Which life cycle stage is found in plants but not animals?
A life cycle in which the only multicellular form is haploid is most typical of __________.
Regardless of whether an organism is an animal, a plant, a fungus, or an algal cell, all zygotes are __________ and are formed during the __________ of two __________ gametes.
diploid; fertilization; haploid
Which of the following occurs in meiosis, but not mitosis?
Homologous chromosomes separate.
A clone is the product of __________.
asexual reproduction and mitosis
The life cycle called __________ in plants has two multicellular stages: the __________ and the __________.
alternation of generations; haploid gametophyte; diploid sporophyte
Which of the following statements about homologous chromosomes is correct?
They have genes for the same traits at the same loci.
Ignoring crossover, how many kinds of gametes can be produced by an organism with a diploid number of 8?
Genetic diversity requires __________.
sexual reproduction, independent assortment, crossing over between nonsister chromatids of homologous chromosomes, and random fertilization
How many genes are present in the human genome?
tens of thousands
A pair of genetic structures carrying genes that control the same inherited characters are called __________.
Regarding the role of cohesin protein in maintaining cohesion between sister chromatids, which of the following statements is false?
During meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms.
The major contribution of sex to evolution is that __________.
it provides a method to increase genetic variation
The zipper-like complex that forms in meiosis occurs during __________ and is called the __________.
prophase I; synaptonemal complex
At the end of mitosis, __________ daughter cells that are genetically __________ are formed, while at the end of meiosis, __________ daughter cells that are genetically __________ are formed.
two; identical; four; distinct
Somatic cells in animals differ from gametes in that somatic cells __________.
are all of the cells of the body except for the gametes and their precursors
Somatic cells in humans contain __________ set(s) of chromosomes and are therefore termed __________.
Somatic cells in humans differs from gametes in that human somatic cells __________.
contain two sets of each of the 23 chromosome types
Unless the chromosomes were stained to show band patterns, a karyotype would be least likely to show which of the following?
Part of a chromosome turned around.
Darwin realized the importance of heritable variation to evolution __________.
even though he never read any of Gregor Mendel’s work
Sister chromatids differ from nonsister chromatids in that sister chromatids __________.
are products of the S phase of the cell cycle and are two copies of one chromosome
The process called __________ reduces the chromosome number by __________.
meiosis; two consecutive cell divisions
Which of the following is a function of mitosis in humans?
Multiplication of body cells
Characteristic of the bdelloid rotifer is that it __________.
is an example of an animal that has not reproduced sexually in 40 million years
The egg (ovum) of a rabbit contains 22 chromosomes. How many chromosomes are in the somatic (body) cells of a rabbit?
What is a locus?
The precise location of a gene on a chromosome.
Allelic variation is an important source of __________ in a population.
__________ are a group of genetically identical individuals produced by a process called __________.
Clones; asexual reproduction
In meiosis, __________ of __________ cross over and form __________.
nonsister chromatids; homologous pairs; chiasmata
What is the result when a diploid cell undergoes meiosis?
Four haploid cells
Which of the following events does not occur during interphase of the cell cycle?
Separation of the sister chromatids
During interphase, the genetic material of a typical eukaryotic cell is __________.
dispersed in the nucleus as long strands of chromatin
Which of the following statements describes a cell that undergoes mitosis but not cytokinesis?
The cell contains more than one nucleus.
Chromatids are __________.
identical copies of each other if they are part of the same chromosome
Observations of cancer cells in culture support the hypothesis that cancer cells __________.
do not exhibit density-dependent inhibition
The function of the mitotic cell cycle is to produce daughter cells that __________.
are genetically identical to the parent cell (assuming no mutation has occurred)
Which of the following events occurs during prometaphase of mitosis?
The nuclear envelope fragments.
Which of the following events does not occur during prophase of mitosis?
The mitotic spindle breaks down.
How does the process of mitosis differ between most eukaryotes and other eukaryotes such as diatoms and dinoflagellates?
The nuclear envelope fragments in most eukaryotes but remains intact in diatoms and dinoflagellates.
DNA replication occurs in __________.
the S phase of interphase in both somatic and reproductive cells
During binary fission in a bacterium __________.
the origins of replication move apart
A cell contains 40 chromatids at the beginning of mitosis. How many chromosomes will it contain at the completion of cytokinesis?
The complex of DNA and protein that makes up a eukaryotic chromosome is properly called __________.
What is the difference between a benign tumor and a malignant tumor?
Cells of benign tumors do not metastasize; those of malignant tumors do.
Which of the following phases of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope?
A cell biologist examined the DNA content of a cell from a fruit fly larva during the G1 phase and determined that it had 150 units of DNA. After measuring the DNA content of the same type of cell after the G2 phase, it was discovered that the cell had 300 units of DNA. How is this possible?
The DNA was replicated during the S phase of interphase, which occurs between the two G phases.
Which of the following statements correctly describes the difference(s) between mitosis and binary fission?
Binary fission involves the replication and division of a single chromosome, whereas mitosis involves the division of multiple, replicated chromosomes.
Which of the following structures is/are part of the mitotic spindle?
All of the listed responses are part of the mitotic spindle.
In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?
Checkpoints in the cell cycle control system __________.
regulate the cell cycle through a variety of stop and go signals
How many chromatids does a human somatic cell contain after interphase and just prior to mitosis?
The region of a chromosome holding the two double strands of replicated DNA together is called __________.
The spread of cancer cells to other locations in the body is known as __________.
You would know a dividing cell was a plant cell rather than an animal cell if you saw that __________.
it had formed a cell plate
Which of the following events occurs during metaphase of mitosis?
The chromosomes align along the metaphase plate of the cell.
Which of the following events occurs during telophase of mitosis?
Two distinct daughter nuclei form in the cell.
Which of the following events occurs during anaphase of mitosis?
The sister chromatids are pulled apart toward opposite sides of the cell.
Cytokinesis refers to __________.
division of the cytoplasm
One event occurring during prophase is __________.
the beginning of the formation of a spindle apparatus
The F1 generation differed from the F2 in Mendel’s experiments in that __________.
all of the F1 showed the dominant phenotype, but only three-fourths of the F2 did
Human ABO groups are best described as an example of __________.
If the two traits that Mendel looked at in his dihybrid cross of smooth yellow peas with wrinkled green peas had been controlled by genes that were located near each other on the same chromosome, then the F2 generation __________.
would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment
In a typical pea experiment, two true-breeding plants with distinct traits of a single character are called the __________, and the offspring are called the __________, which will always be __________.
P (or parental) generation; F1 (or first filial) generation; hybrid
If an organism that is homozygous dominant is crossed with a heterozygote for that trait, the offspring will be __________.
all of the dominant phenotype
Pea plants are tall if they have the genotype TT or Tt, and they are short if they have genotype tt. A tall plant is mated with a short plant. Which outcome below would indicate that the tall parent plant was heterozygous?
The ratio of tall offspring to short offspring is 1:1.
Color in squash is controlled by epistatic interactions in which color is recessive to no color. At the first locus white squash (W) is dominant to colored squash (w). At the second locus yellow (Y) is dominant to green (y). What is the phenotype of a squash with the genotype wwYy?
A man who can roll his tongue and a woman who cannot roll her tongue have a son who can roll his tongue (R = can roll tongue; r = can’t roll tongue). The son is curious about whether his father is homozygous or heterozygous for the tongue-rolling trait. Which of the following facts would allow him to know?
His father’s mother cannot roll her tongue.
In Labrador retrievers, a dog that has the genotype BBee, where BB produces black-pigmented fur and ee produces yellow-pigmented fur, would have __________ fur and would exhibit __________.
Which choice below is a basic difference between Mendel’s particulate hypothesis and the hypothesis of blending inheritance?
The blending inheritance hypothesis, but not the particulate hypothesis, maintained that after a mating, the genetic material provided by each of the two parents is mixed in the offspring, losing its individual identity.
Achondroplasia, a type of dwarfism, and Huntington’s disease are examples of __________, with the exception that the Huntington’s allele is __________.
dominant inherited disorders; lethal
If a plant variety is true-breeding for a dominant trait, then __________.
if the plant were allowed to self-pollinate, all of the progeny would have the dominant trait
In addition to the ABO system, humans have other blood groups, including the MN system. Individuals who have alleles for both M and N show __________ for the M and N red blood cell surface antigens.
Human blood groups are governed by three alleles, A, B, and O. A and B are codominant and O is recessive to both. A man who has type B blood and a woman who has type A blood could have children of which of the following phenotypes?
A, B, AB, or O
Mendel’s law of segregation states that __________
the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes
In humans, height and skin color have continuous variation in the population because of __________.
The effect of the environment on a phenotype is referred to as __________.
In incomplete dominance, the offspring __________.
will have an appearance that’s intermediate between those of the two parental types
An alternative version of a gene is called a(n) __________.
Huntington’s disease is an example of a genetic disorder caused by __________.
a lethal dominant allele that afflicts an individual later in life
In people with sickle-cell disease, red blood cells break down, clump, and clog the blood vessels. The blood vessels and the broken cells accumulate in the spleen. Among other things this leads to physical weakness, heart failure, joint pain, and brain damage. Such a suite of symptoms can be explained by __________.
the pleiotropic effects of the sickle-cell allele
Fetal cells may be removed along with fluid from the womb by a process known as __________.
If a heterozygous plant is allowed to self-pollinate, what proportion of the offspring will also be heterozygous?
A red bull is crossed with a white cow and all of the offspring are roan, an intermediate color that is caused by the presence of both red and white hairs. This is an example of genes that are __________.
What kind of protection does the Genetic Information Nondiscrimination Act of 2008 provide the public with regard to the use of genetic information?
The law prohibits the use of genetic test information to deny insurance coverage or employment to individuals.
Mendel studied __________, heritable features that vary among individuals; each variant is called a __________.
__________ occurs when a single gene affects the phenotype of many characters in an individual.
A pleiotropic effect
The term “true-breeding plants” means __________.
that self-pollinating plants will always produce the same trait of a particular character
Besides the fact that pea plants have a short generation time, the key to Mendel’s successful plant-breeding experiments was that pea plants usually __________.
A family tree that describes traits in families is called a __________.
Gene silencing is called __________.
In an X-linked, or sex-linked, trait, it is the contribution of __________ that determines whether a son will display the trait.
The chromosome theory of inheritance states that __________.
genes occupy specific positions on chromosomes, homologous chromosomes segregate from each other during meiosis, and chromosomes assort independently during meiosis
In Klinefelter syndrome, individuals are phenotypically male, but have reduced sperm production and may have some breast development in adolescence. The cells of Klinefelter individuals have two X chromosomes and one Y (they are XXY instead of XY).
This occurs because of what meiotic error?
What appears to be the mechanism for genomic imprinting?
DNA methylation that silences particular genes and DNA methylation that activates particular genes
X inactivation occurs when there is/are at least __________ X chromosomes present in an individual, forming a structure called a __________ by a __________ event.
two; Barr body; random
Down syndrome is an example of __________, and the child is __________ for chromosome 21.
Linked genes __________.
are located near each other on the same chromosome
With a microscope, you examine some somatic cells from a woman and notice that each nucleus has two Barr bodies. What can you infer about the sex chromosomes in this individual?
She is XXX.
Wild type refers to __________.
the most common phenotype thought to be found in the natural population
Genomic imprinting in mammals appears to primarily affect genes involved in __________.
Duchenne muscular dystrophy is caused by a sex-linked recessive allele. Its victims are almost invariably boys, who usually die before the age of 20. Why is this disorder almost never seen in girls?
To express an X-linked recessive allele, a female must have two copies of the allele.
Why did Morgan choose Drosophila for his genetics experiments?
A single mating can produce many offspring and Drosophila chromosomes can be easily distinguishable under a light microscope.
In a certain fish, fin rays (supporting structures for the fins) can be either bony or soft in adult fish. Sex linkage in a fish is similar to that in humans. What evidence would most strongly support the idea that the ray locus is on the X chromosome?
Matings of soft ray males and bony ray females give different results from the matings of bony ray males and soft ray females.
Female mammals have two X chromosomes, one from their mother and one from their father. During X inactivation, one X chromosome in each embryonic cell is randomly inactivated; therefore, all of the tissues that arise from that cell have the same inactivated X chromosome. Female mammals are therefore considered to be __________ of the maternal and paternal cells.
In humans, a normal male’s somatic cells will have __________ set(s) of chromosomes and sex chromosomes designated as __________ and __________, while in bees and ants, a normal male’s somatic cells have __________ set(s) of chromosomes, which are __________.
two; X; Y; one; haploid
In X-linked patterns of inheritance, __________.
fathers pass X-linked alleles only to their daughters, and mothers pass X-linked alleles to both their daughters and their sons
In werewolves (hypothetically), pointy ears (P) are dominant over round ears (p). The gene is on the X chromosome. (Sex determination in werewolves is the same as for “other” humans.) A certain female werewolf has pointy ears even though her father had round ears.
What percentage of her sons will have round ears if she mates with a werewolf with round ears?
A linkage map __________.
orders genes on a chromosome based on recombination frequencies
When crossing over occurs between two linked genes in an F1 dihybrid testcross, the frequency of the parental types will always __________ the frequency of the recombinant types when compared to Mendel’s unlinked genes.
be greater than
Examples of alterations of chromosomal structures include all of the following except __________.
In a cross between wild-type (red-eyed) female flies and mutant white-eyed male flies, the F1 generation should always produce females with __________ eyes and males with __________ eyes.
Individuals with an extra X chromosome __________.
may have subnormal intelligence or be at risk for learning disabilities
You perform a testcross using F1 dihybrid flies. If, in the resulting offspring, the percentages of parental and recombinant offspring are about the same, this would indicate that the two genes are __________.
The __________ states that genes have specific positions on chromosomes and that chromosomes undergo both __________ and __________.
chromosomal theory of inheritance; segregation; independent assortment
Compared to peas, fruit flies were thought to have no variations, until the discovery of a __________ fly by __________.
male white-eyed; Morgan
When an individual has an additional chromosome, that chromosome set is called __________, and the condition is known as __________.
The ability to observe meiosis in gamete production supported Mendel’s first law of __________, which applies when __________ separate, and supported Mendel’s second law of __________, which applies when __________ sort __________.
segregation; homologous pairs; independent assortment; alleles; independently
__________ is the failure of __________ to separate in meiosis I or the failure of __________ to separate in meiosis II.
Nondisjunction; homologous chromosomes; sister chromatids
Queen Victoria was a carrier of a recessive sex-linked allele for hemophilia. Which of the following possibilities could explain the presence of the hemophilia allele in her genotype?
Either her mother was a carrier or her father had hemophilia.
In DNA replication, the next nucleotide is incorporated into the growing polymer at the __________ of the molecule by an enzyme called __________.
3ꞌ (hydroxyl) end; DNA polymerase
The role of DNA polymerases in DNA replication is to __________.
attach free nucleotides to the new DNA strand
The information in DNA is contained in __________.
the sequence of nucleotides along the length of the two strands of the DNA molecule
DNA replication begins at a site called the origin of replication, forming a bubble, which is followed by a __________, where parental strands are unwound by __________.
replication fork; helicases
Which description of DNA replication is correct?
Helicases separate the two strands of the double helix, and DNA polymerases then construct two new strands using each of the original strands as templates.
The overall error rate in the completed DNA molecule is approximately __________.
1 error per 10,000,000,000 nucleotides
DNA polymerase adds nucleotides to the __________ of the leading strands, and to the __________ of the lagging strands (Okazaki fragments).
3′ end; 3′ end
In the famous Hershey and Chase “blender experiment,” radioactive sulfur was used to label __________, and radioactive phosphorus was used to label __________, demonstrating that the genetic material of a bacteriophage is __________.
protein; DNA; DNA
When __________ form after an exposure to ultraviolet (UV) light, a __________ can remove the damaged nucleotides and replace them with normal nucleotides.
thymidine dimers; nucleotide excision repair enzyme
In bacterial DNA replication of the lagging strand, __________ is required for the synthesis of a new DNA strand whereas __________ is required for removing the RNA primer and replacing it with DNA nucleotides.
DNA polymerase III; DNA polymerase I
X-ray diffraction images produced by __________ showed that DNA is a __________.
Franklin; double helix
Proteins that are involved in packaging the eukaryotic chromosome into “beads” called __________ are __________.
Griffith showed that dead __________ cells __________ living __________ cells into living __________ cells.
pathogenic; transform; nonpathogenic; pathogenic
What is the major difference between bacterial chromosomes and eukaryotic chromosomes?
Bacteria have a single circular chromosome whereas eukaryotes have several linear chromosomes.
In DNA, the two purines are __________, and the two pyrimidines are __________.
adenine and guanine; cytosine and thymine
One strand of a DNA molecule has the base sequence 5′-ATAGGT-3′. The complementary base sequence on the other strand of DNA will be 3′-__________-5′.
Replication of the lagging strand of DNA is accomplished by repeatedly making __________ followed by 1,000-2,000 nucleotide segments called __________.
short RNA primers; Okazaki fragments
Of the three alternative models of DNA replication, which are the __________ models, the one that explains how DNA replicates is the __________ model.
conservative, semiconservative, and dispersive; semiconservative
Telomeres are __________.
repeating noncoding sequences at the ends of linear eukaryotic chromosomes
Evidence to support that DNA strands run antiparallel to each other includes all of the following except __________.
that the sugar-phosphate backbones are to the inside of the molecule
Chargaff analyzed DNA and found that the numbers of adenine molecules is approximately equal to the numbers of __________ molecules and that the numbers of __________ molecules is approximately equal to the numbers of __________ molecules.
thymine; guanine; cytosine
The 5ꞌ end of a DNA strand always has a free __________ group while the 3ꞌ end always has a free __________ group.
In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?
A + G = C + T
The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is relieved by an enzyme called __________.
Who is credited with explaining the structure of the DNA double helix?
Watson and Crick
The two sugar-phosphate strands that form the rungs of a DNA double helix are joined to each other through __________.
hydrogen bonds between nucleotide bases
The experiments of Meselson and Stahl showed that DNA __________.
replicates in a semiconservative fashion
A virus that infects bacteria is called a __________, which is made up of the macromolecules __________ and __________.
bacteriophage; DNA; protein
Which of the following components is required for DNA replication?
Which of the following catalyzes the linkage between ribonucleotides to form RNA during gene expression?
An exception to the one gene-one enzyme hypothesis is __________.
that not all genes code for enzymes; some genes code for structural proteins such as keratin
One strand of a DNA molecule has the following sequence: 3-AGTACAAACTATCCACCGTC-5.
In order for transcription to occur in that strand, there would have to be a specific recognition sequence, called a(n) __________, to the left of the DNA sequence indicated.
In eukaryotic cells, a __________ by a __________ targets a growing peptide to the endoplasmic reticulum.
signal peptide; signal-recognition particle
__________ is the synthesis of RNA using information in the DNA.
The bonds that hold tRNA molecules in the correct three-dimensional shape are __________.
The structures called snRNPs are __________.
part of a spliceosome
Which of the following best describes the arrangement of genetic information in a DNA molecule?
The three-nucleotide words of a gene are arranged in a nonoverlapping series on the DNA template strand.
How many nucleotides are needed to code for a protein with 450 amino acids?
at least 1,350
By bombarding the fungus Neurospora crassa with X-rays, Beadle and Tatum were able to study __________ and characterize enzymes in a __________.
nutritional mutants; biochemical pathway
The “triplet code” refers to the fact that _________.
three nucleotides code for a single amino acid
__________ is the synthesis of a polypeptide using information in the mRNA.
Bacteria can transcribe and translate human genes to produce functional human proteins because __________.
the genetic code is nearly universal
Polysomes may be defined as __________.
groups of ribosomes
RNA molecules that function as enzymes are called __________.
Gene expression is __________.
the process by which DNA directs the synthesis of proteins
The sickle-cell β-globin mutation is an example of a __________.
Stop codons are unique because they __________.
do not code for amino acids that allow a releasing factor to bind to the A site of the ribosome
When RNA is being made, the RNA base _________ always pairs with the base __________ in DNA.
Insertions and deletions are called __________ mutations.
Which of the following is a post-translational modification of a polypeptide?
Cleavage of a polypeptide into two or more chains
Who formulated the one gene-one enzyme hypothesis?
Beadle and Tatum
What is a key difference in gene expression between eukaryotic and prokaryotic cells?
In prokaryotic cells, the mRNA transcript is immediately available as mRNA without processing.
The function of tRNA during protein synthesis is to __________.
deliver amino acids to their proper site during protein synthesis
Eukaryotic processing of the primary transcript includes __________.
the addition of a 5ꞌ cap, a 3ꞌ poly-A tail, and the splicing out of introns
Genetic information of eukaryotic cells is transferred from the nucleus to the cytoplasm in the form of __________.
What is the proper order of the following events in the expression of a eukaryotic gene?
2. RNA processing
4. modification of protein
3, 2, 1, 4
Because the bacterial cell’s DNA is not surrounded by a nuclear envelope, __________ occur(s).
coupled transcription and translation
The type of point mutation that results in a premature stop codon is called a _________ mutation.
The TATA box is a __________ that allows for the binding of __________ and __________.
eukaryotic promoter; transcription factors; RNA polymerase II
In a eukaryote, activating transcription factors may stimulate gene expression by binding to a DNA site called a(n) __________.
A cancer cell __________.
does not respond to the chemical signals that control cell division
In Drosophila development, pattern development in the late embryo, larva, and adult is controlled by __________.
In the trp (tryptophan) operon, the __________ binds to the product of the trp operon synthesis pathway, called __________, forming the __________.
repressor protein; tryptophan; active corepressor
The trp (tryptophan) operon is an example of a(n) __________ operon.
In addition to a promoter, eukaryotic genes have control elements called __________.
proximal control elements and distal enhancers
Post-transcriptional processing of a pre-mRNA allows for differential cell expression by a process called __________.
What is the role of proteasomes?
They are giant protein complexes that recognize ubiquitin and degrade the tagged proteins.
What two genes are often mutated in colon cancer?
ras and p53
Chemotherapeutic treatment for breast cancer depends on the absence or overexpression of the __________ gene(s).
ERa, PR, and HER2
In the lac operon, the inducer is __________.
allolactose, the isomer of lactose
Which of the following best describes the makeup of the human genome?
Genes for noncoding RNA make up the majority of meaningful genetic information in the human genome.
The trp (tryptophan) operon is an example of a(n) __________ that is controlled by __________.
anabolic pathway; feedback inhibition
In prokaryotic genomes, groups of functionally related genes along with their promoters and operators are found together in __________.
Although the number of genes in the human genome is surprisingly low compared to less complex organisms, the number of possible products from those genes is greatly amplified by __________.
alternate arrangements of exons from a primary transcript
MyoD promotes muscle cell development by __________.
turning on the expression of multiple muscle-related genes
In eukaryotes, histone acetylation __________.
The control of gene expression is more complex in multicellular eukaryotes than in prokaryotes because __________.
in a multicellular eukaryote, different cells are specialized for different functions
In general, operons that encode the enzymes of a biosynthetic (anabolic) pathway (such as the trp operon) are __________, and those encoding the enzymes of a catabolic pathway (such as the lac operon) are __________.
In Drosophila development, the anterior-posterior axis of the embryo is determined by __________.
Gene expression in bacteria is regulated primarily by __________.
controlling the transcription of genes into mRNA
Specific cells that appear undifferentiated under the microscope but are already fated to become muscle cells are called __________.
In an inducible operon, the inducer is often the __________ in the pathway being regulated; the inducer binds to the __________, thus rendering it __________.
substrate; repressor; inactive
Small noncoding RNAs (ncRNAs) called piwi-interacting RNAs, or piRNAs, __________.
induce the formation of heterochromatin and block the expression of movable DNA elements called transposons
What gene has been called the “guardian angel of the genome?”
the p53 gene
MicroRNAs binding to complementary sequences on an mRNA __________.
results in either blocking translation or degrading the targeted mRNA
Cell type-specific transcription is accomplished __________.
by specific enhancer control elements interacting with cell type-specific transcription factors
Both repressible and inducible operons control gene expression at the level of __________.
Cytoplasmic determinants __________.
are RNAs, proteins, and other substances produced by the mother and deposited in the egg
The lac operon is an example of a(n) __________ operon.
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.
three … amino acid
What does it mean when we say the genetic code is redundant?
More than one codon can specify the addition of the same amino acid.
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the _____.
binding of the anticodon to the codon and the attachment of amino acids to tRNAs
For a repressible operon to be transcribed, which of the following must occur?
RNA polymerase must bind to the promoter, and the repressor must be inactive.
How is translation initiated?
The small ribosomal subunit binds to the mRNA.
The tRNA bearing methionine binds to the start codon.
The large ribosomal subunit binds to the small one.
The start codon signals the start of translation.
One way to detect alternative splicing of transcripts from a given gene is to _____.
compare the sequences of different mRNAs made from the given gene
What would the anticodon be for a tRNA that transports phenylalanine to a ribosome?
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is _____.
In the process of transcription, _____.
RNA is synthesized
Which of the following is the first event to take place in translation in eukaryotes?
the small subunit of the ribosome recognizes and attaches to the 5′ cap of mRNA
According to the lac operon model proposed by Jacob and Monod, what is predicted to occur if the operator is removed from the operon?
The lac operon would be transcribed continuously.
Codons are part of the molecular structure of _____.
A lack of which molecule would result in a cell’s inability to “turn off” genes?
A nonsense mutation in a gene _____.
introduces a premature stop codon into the mRNA
After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence?
introns … exons
DNA methylation and histone acetylation are examples of _____.
The flow of information in a cell proceeds in what sequence?
from DNA to RNA to protein
What is the function of RNA polymerase?
It unwinds the double helix and adds nucleotides to a growing strand of RNA.
The mitotic spindle is a microtubular structure that is involved in _____.
separation of sister chromatids
Sister chromatids separate from each other during _____.
mitosis and meiosis II
Which of the following is true of kinetochores?
They are sites at which microtubules attach to chromosomes.
In human and many other eukaryotic species’ cells, the nuclear membrane has to disappear to permit _____.
the attachment of microtubules to kinetochores
The first gap in the cell cycle (G1) corresponds to _____.
normal growth and cell function
Metaphase is characterized by _____.
aligning of chromosomes on the equator
In eukaryotic cells, chromosomes are composed of _____.
DNA and proteins
Which of the following occurs during meiosis but not during mitosis?
A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
What do we mean when we use the terms monohybrid cross and dihybrid cross?
A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied.
In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?
Which of the following is the best statement of the use of the addition rule of probability?
the probability that either one of two independent events will occur
Consider pea plants with the genotypes GgTt and ggtt . These plants can each produce how many type(s) of gametes?
four … one
Which of the following provides an example of epistasis?
In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.
In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?
What is the function of helicase in DNA replication?
It untwists the double helix and separates the two DNA strands.
Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
XNXn and XNY
When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?
The gene involved is on the X chromosome.
DNA replication is said to be semiconservative. What does this mean?
Each new double helix consists of one old and one new strand.
How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?
It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.
Normally, only female cats have the tortoiseshell phenotype because _____.
a male inherits only one allele of the X-linked gene controlling hair color
Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
Which of the following statements describes chromatin?
Heterochromatin is highly condensed, whereas euchromatin is less compact.