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187 Cards in this Set

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through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely
a plant cell in the process of cytokinesis.
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of micro-tubules, its effectiveness must be related to
disruption of mitotic spindle formation.
One difference between cancer cells and normal cells is that cancer cells
continue to divide even when they are tightly packed together.
The decline of MPF activity at the end of mitosis is due to
the degradation of cyclin.
In the cells of some organisms, mitosis occurs without cytoki-nesis. This will result in
cells with more than one nucleus
Which of the following does not occur during mitosis?
DNA replication
A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in
G1
The drug cytochalasin B blocks the function of actin. Which of the following aspects of the animal cell cycle would be most disrupted by cytochalasin B?
cleavage furrow formation and cytokinesis
The person credited with first recognizing (in the 1860s) that living cells cannot arise spontaneously, but arise only from previously existing cells, is
Rudolf Virchow
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 is false regarding sister chromatids?
Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred.
The complex of DNA and protein that makes up a eukaryotic chromosome is properly called _
chromatin
The region of a chromosome holding the two double strands of replicated DNA together is called ____
a centromere
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 is false regarding sister chromatids?
Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred.
The complex of DNA and protein that makes up a eukaryotic chromosome is properly called
chromatin
The region of a chromosome holding the two double strands of replicated DNA together is called _
a centromere
The centromere is a region in which
sister chromatids are attached to one another in prophase
How many maternal chromosomes are present in a somatic human cell not engaged in cell division?
23
"Cytokinesis" refers to
division of the cytoplasm
Chromatids are __
identical copies of each other if they are part of the same chromosome
If a cell contains 60 chromatids at the start of mitosis, how many chromosomes will be found in each daughter cell at the completion of the cell cycle?
30
A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in the cells doubled
between the G1 and G2 phases
A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA at G1 of the cell cycle in one of the grasshopper daughter cells?
100 units
During interphase, the genetic material of a typical eukaryotic cell is _
dispersed in the nucleus as long strands of chromatin
DNA replication occurs in _
the S phase of interphase in both somatic and reproductive cells
If a somatic human cell is just about to divide, it has _____ chromatids
92
Down syndrome is characterized by cells having three copies of chromosome 21. As a cell in an individual with Down syndrome prepares to enter mitosis, how many chromatids would be present?
94
Which of the following does NOT occur during mitosis?
replication of chromosomes
During what phase in the cell cycle would you find the most DNA per cell?
G2
In telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _
prophase
Which of the following phases of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope?
telophase
Assume that you are dealing with a species in which the number of chromosomes in each somatic cell is 14. How many sister chromatids are present in the early telophase of mitosis?
0
In a human skin cell that is going through the cell cycle, when do the centrosomes separate?
prophase
Following cytokinesis in an animal cell, how many centrioles does each new daughter cell possess?
two
The phase of mitosis during which the chromosomes move toward separate poles of the cell is
anaphase
One event occurring during prophase is
the beginning of the formation of a spindle apparatus
Which event or events occur during anaphase?
All of the listed responses are correct.
Which of the following represents a mismatch or incorrect description?
metaphase: the nuclear envelope disappears
During which stage of the cell cycle do sister chromatids separate?
anaphase
In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?
cytokinesis
At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?
metaphase
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 processes does NOT occur in dividing bacteria?
mitosis
During binary fission in a bacterium ____
the origins of replication move apart
Which of the following is involved in the binary fission of bacteria?
distribution of a copy of the single parental chromosome to each daughter cell
When a cell in S phase is fused with a cell in G1
DNA synthesis begins immediately in the original G1 nucleus
Tissue culture experiments with PDGF demonstrate that without this substance
fibroblasts fail to divide
You would be unlikely to see which of the following human cells dividing?
nerve cell
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 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.
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
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
A = big apples; R = red apples; a = small apples; r = yellow apples. You have one tree that produces big yellow apples and another tree that produces small red apples. When the two are crossed, you find that half of the new trees produce big red apples and half produce big yellow apples. What are the genotypes of the parents?
AArr and aaRr
No. Trees that produce big yellow apples could be AArr or Aarr. Trees that produce small red apples could be aaRR or aaRr. Because all the offspring are big, the big parent must be homozygous for A. Because half the apples are red and half are yellow, the red parent must be heterozygous for red. The conclusion is that the cross must be AArr x aaRr.
Assume tall (T) is completely dominant to dwarf (t) in a certain species of plant. If a homozygous dominant individual is crossed with a homozygous dwarf, the offspring will
all be tall
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
Physically, what are different alleles?
Different alleles are different DNA sequences found at the same locus on homologous chromosomes.
In a certain plant, the alleles A, B, and C are completely dominant to the alleles a, b, and c. A plant with the genotype AABbcc will have the same phenotype as a plant with the genotype _____
AaBBcc
This genotype expresses a phenotype that is dominant for all three characters.
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.
What is indicated when a single-character testcross yields offspring that all have the dominant phenotype?
The parent with the dominant phenotype was homozygous.
If an organism that is homozygous dominant is crossed with a heterozygote for that trait, the offspring will be _____
all of the dominant phenotype
In Mendel's monohybrid cross of purple-flowered and white-flowered peas, all members of the F1 generation had the _____ phenotype because their genotype was _____ at the flower-color locus.
purple-flowered ... heterozygous
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
the law of independent assortment ___
look up
Homologous pairs of chromosomes often
contain different alleles
f each parent can produce 100 genetically distinct gametes, how many genetically distinct offspring can two parents produce?
10,000
Pea flowers may be purple (P) or white (p). Pea seeds may be round (R) or wrinkled (r). What proportion of the offspring from the cross PpRr x PpRr will have white flowers and wrinkled seeds?
1/16
An AABbccDdEeFF individual is crossed with an individual with the genotype AaBBCCDdEeff. What is the probability that their offspring will have the genotype AaBBCcddEEFf?
1/64
If a heterozygous plant is allowed to self-pollinate, what proportion of the offspring will also be heterozygous?
1/2
An individual with the genotype AABbCcDD can make how many different kinds of gametes?
4
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 ___
codominant
Flower color in snapdragons is an example of incomplete dominance. When a red-flowered plant is crossed with a white-flowered plant, the F1 generation has pink flowers. If a pink-flowered plant is crossed with another pink-flowered plant, the progeny plants will be ____
25% red, 50% pink and 25% white
Which choice below describes the expression of Tay-Sachs disorder in humans at the biochemical level?
incompletely dominant
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
Which of the following matings cannot produce a child with blood type O? The letters refer to blood types (phenotypes)
O x AB
A woman with type O blood is expecting a child. Her husband is type A. Both the woman's father and her husband's father had type B blood. What is the probability that the child will have type O blood?
50%
A single genetic locus that controls more than one trait is said to be _____.
pleiotropic
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?
yellow
Tail length in a certain species of armadillo falls along a continuum, following a normal distribution. Assuming that environmental factors do not play an important role in determining tail length, this type of variation probably reflects _____.
polygenic inheritance
Mendel's theory of particulate inheritance ____
can explain inheritance patterns for virtually every sexually reproducing organism but does not explain multifactorial characters
Tay-Sachs disease runs in Rebecca's family. On a family pedigree, she saw a shaded circle. This represented a ___
female with Tay-Sachs
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 fathers mother cannot roll her tongue
Michelle and Keith are apparently normal, but their daughter was born with alkaptonuria, an inherited metabolic disorder. If alkaptonuria is like most other human hereditary disorders, the probability of their next child being born with alkaptonuria is _____.
1/4
Correct. The probability of their next child having alkaptonuria is one-fourth because they are both heterozygous (carriers) for the trait.
Tom's brother suffers from phenylketonuria (PKU), a recessive disorder. The brothers' parents do not have PKU. What are the chances that Tom, who is normal for this trait, is a carrier of PKU?
2/3
A couple, both descended from eastern European (Ashkenazic) Jews, visit a genetic counselor before trying to have children. In view of their ethnic background, the counselor recommends that they be tested to see if they are carriers for ____
Tay-Sachs
Cystic fibrosis, which is usually lethal before the age of reproduction, is a homozygous recessive trait. Why do cases continue to arise, even though people with the disease rarely live to reproduce?
The harmful allele "hides" within heterozygous individuals, and one-fourth of the offspring of two heterozygotes would be afflicted.
The genetic disease cystic fibrosis is caused by a defective allele that _____.
encodes a defective chloride-channel membrane transport protein
When two average-height parents give birth to a child exhibiting achondroplasia, it is most likely due to a new mutation. This is because _____
achondroplasia is caused by an allele that is always expressed, therefore the parents must not have the allele
Correct. Achondroplasia, a form of dwarfism, is due to a dominant allele.
It is far more common to find human genetic disease caused by _____ alleles than by _____ alleles because _____.
recessive ... dominant ... harmful recessive alleles can survive in the heterozygote without any selection pressure against them
Huntington's disease is an example of a genetic disorder caused by _____
a lethal dominant allele that afflicts an individual later in life
Heart disease, diabetes, cancer, alcoholism, and many mental illnesses can best be described as _____.
multifactorial disorders with a possible polygenic component
Correct. These disorders involve several genes and environmental factors.
Fetal cells may be removed along with fluid from the womb by a process known as _____.
amniocentesis
In which genetic testing procedure would a physician remove a small tissue sample from a membrane of fetal genetic origin?
chorionic villus sampling
Correct. The cells sampled are derived from the fetus; therefore, a karyotype of the fetus can be created using these cells.
How does codominance at the molecular level help to explain why evolutionary processes haven't resulted in the elimination of the sickle-cell allele among people of African descent?
Individuals with normal and sickle-cell hemoglobin in their red blood cells are usually healthy and, when infected by the malaria parasite, have lower parasite densities and, thus, reduced malaria symptoms.
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.
Correct. The law was enacted to allay fears by people opting for genetic testing that the results from such tests could be used against them by health insurance companies or potential employers.
Wild type refers to _____
the most common phenotype thought to be found in the natural population
Which of the following results of Thomas Hunt Morgan's experiments with white-eyed mutant flies was unexpected in light of Mendelian genetics?
Among the F2 progeny, only males had white eyes. All of the females had red eyes.
What is the probability that a male will inherit an X-linked recessive allele from his father?
0%
In an X-linked, or sex-linked, trait, it is the contribution of _____ that determines whether a son will display the trait
the mother
If a mother is heterozygous for a recessive sex-linked trait and her husband has the dominant allele, which one of the following is true about the probabilities for their children?
Half of their sons will have the recessive trait.
Correct. All the sons will receive Y chromosomes from their father. The X must come from the heterozygous mother; therefore, each son has a 50% chance of inheriting the recessive allele.
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?
50%

The female werewolf must be heterozygous, because her father has round ears. Each of her sons has a 50% chance of inheriting the round allele.
A woman is red-green color-blind. What can we conclude, if anything, about her father?
he is red-green color-blind
A woman is a carrier for red-green color blindness, a sex-linked trait. Her husband is normal (not color-blind) for this trait. What are the chances that their newborn daughter will be red-green color-blind?
0%
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.
Hemophilia is a sex-linked disorder. The daughter of a father with hemophilia and a carrier mother has a _____ probability of having hemophilia.
50%
Correct. The mother is XHXh, and the father is XhY. The daughter must receive Xh from the father and has a 50% chance of receiving Xh from the mother.
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.
A genetic defect in humans results in the absence of sweat glands in the skin. Some men have this defect all over their bodies, but in women it is usually expressed in a peculiar way: A woman with this defect typically has small patches of skin with sweat glands and other patches without sweat glands. In women, the pattern of sweat-gland distribution can best be explained by _____.
Correct Answer:

X chromosome inactivation
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.
X-linked genes differ from Y-linked genes in which of the following ways
ons and daughters have equal probabilities in inheriting a recessive allele of an X-linked gene from their mother, but only sons can inherit rare Y-linked genetic disorders from their father.
Which of the following best describes the function of the XIST gene in X chromosome inactivation?
The XIST gene on the X chromosome to be inactivated is expressed to produce multiple RNA transcripts that bind to that chromosome and effectively cover it up, thereby generating a Barr body.
If two genes are linked, _____.
they are on the same chromosome
In a particular species of mammal, black hair (B) is dominant to green hair (b), and red eyes (R) are dominant to white eyes (r). When a BbRr individual is mated with a bbrr individual, offspring are produced in a ratio of 5 black hair and red eyes:5 green hair and white eyes:1 black hair and white eyes:1 green hair and red eyes. Which of these explanations accounts for this ratio?
The genes for hair color and eye color are linked.
A gray-bodied, vestigial-winged fly is crossed with a black-bodied, normal-winged fly. The F1 progeny is testcrossed. Among the resulting offspring, _____ is a parental type, and _____ is a recombinant type.
black-bodied, normal-winged ... black-bodied, vestigial-winged
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 _____
unlinked
The recombination frequency between two gene loci is ____
greater as the distance between the two loci increases
Four genes (A, B, C, and D) are on the same chromosome. The recombination frequencies are as follows: A-B: 19%; B-C: 14%; A-C: 5%; B-D: 2%; A-D: 21%; C-D: 16%. Based on this information, which sequence of genes is correct?
ACBD
A linkage map _____
orders genes on a chromosome based on recombination frequencies
Correct. A linkage map presents the correct order of genes on the chromosome, although it is not necessarily an accurate representation of the actual distances between genes.
Because the frequency of crossing over is not uniform along the length of a chromosome, _____
map units do not necessarily correlate to physical distances along the chromosome
Correct. Map units reflect recombination frequency, but not physical distance.
Which of the following would result in genetic variation by way of new combinations of alleles?
The first three responses are correct.
Individuals with an extra X chromosome _____
may have subnormal intelligence or be at risk for learning disabilities
During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as ____
nondisjunction
Correct. In nondisjunction, chromosomes fail to separate properly at meiosis.
cells that have a number of chromosomes different from the normal number for their species are known as _____
aneuploid
____ is usually less severe than _____, and _____ species have been observed in plants, fish, amphibians, and even mammals.
Polyploidy ... aneuploidy ... polyploid
Correct. Polyploidy appears to disrupt genetic balance less than aneuploidy, and it has been observed among animals and especially plants.
Gene A is normally found on chromosome number 15 in humans. If amniocentesis reveals fetal cells containing gene A on chromosome 17, but not on 15, the best explanation would be that _____.
translocation occurred
The chromosomal abnormality in which a fragment of a chromosome breaks off and then reattaches to the original chromosome in the same place but in the reverse direction is called _____.
inversion
Correct. As the name suggests, an inversion is a backward piece of a chromosome.
When a person has Down syndrome, he or she has an extra chromosome 21. Therefore, Down syndrome is a kind of _____ and results from _____
aneuploidy ... nondisjunction of chromosome 21 during meiosis I
A person with two X chromosomes and one Y chromosome would appear to be _____
male
Which of the following is the only known viable human monosomy?
XO
Which type of chromosomal alteration is responsible for the cri du chat syndrome?
deletion
Correct. A specific deletion from chromosome 5 leads to this disorder, which is characterized by mental retardation, small head and unusual facial features, and a cry that sounds like a distressed cat.
What appears to be the mechanism for genomic imprinting?
both the first and third listed responses
Genomic imprinting in mammals appears to affect primarily genes involved in _____
embryonic development
Both chloroplasts and mitochondria _____
carry extranuclear genes
Correct. Both chloroplasts and mitochondria carry extranuclear genes.
During Griffith's experiments with Streptococcus pneumoniae in mice, material from _____ bacteria transformed _____ bacteria
heat-killed virulent ... living nonvirulent
Avery and his colleagues' 1944 experiment showed that DNA _____.
was the substance that transformed the bacteria in Griffith's experiment
A scientist assembles a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have _____
the protein and DNA of T4
n an important experiment, a radioactively labeled bacteriophage was allowed to infect bacteria. In a first trial, the phage contained radioactive DNA, and radioactivity was detected inside the bacteria. Next, phage containing radioactive protein was used, and the radioactivity was not detected inside the bacteria. These experiments led to the conclusion that _____.
the genetic material of the phage is DNA
Up until Hershey and Chase showed that DNA was the genetic molecule, what molecule was considered the best candidate for carrying genetic information and why?
proteins because they were thought to be the only molecule with both the variety and specificity of function to account for the array of heritable traits observed
Monomers for the synthesis of DNA are called _____
nucleotides
Chargaff found that for DNA _____.
the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1
What technique was most helpful to Watson and Crick in developing their model for the structure of DNA?
X-ray crystallography
In DNA, the two purines are _____, and the two pyrimidines are _____.
adenine and guanine ... cytosine and thymine
Which of the following is correct?
Adenine forms two hydrogen bonds with thymine; guanine forms three hydrogen bonds with cytosine.
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 information in DNA is contained in _____.
the sequence of nucleotides along the length of the two strands of the DNA molecule
Who is credited with explaining the structure of the DNA double helix?
Watson and Crick
Which of the following attributes of DNA is most crucial to its accurate duplication?
its specific base pairing and hydrogen bonding
During the replication of DNA, _____.
both strands of a molecule act as templates
The experiments of Meselson and Stahl showed that DNA _____.
replicates in a semiconservative fashion
The DNA structures of prokaryotes and eukaryotes are different in several ways, but one way in which they are the same is that
both have a sugar-phosphate backbone
At each end of a DNA replication bubble is _____.
a replication fork
The role of DNA polymerases in DNA replication is to _____
attach free nucleotides to the new DNA strand
The rate of elongation in prokaryotes is _____ the rate in eukaryotes.
much faster than
The two strands of a DNA double helix are antiparallel. This means that _____.
one strand runs in the 5' to 3' direction, and the other runs in the 3' to 5' direction
Correct. This allows the two strands to fit together properly.
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′.
TATCCA
DNA polymerase adds nucleotides to the _____ of the leading strands, and to the _____ of the lagging strands
3' end...3' end
What enzyme joins Okazaki fragments?
topoisomerase
After the formation of a replication bubble, which of the following is the correct sequence of enzymes used for the synthesis of the lagging DNA strand?
helicases, primase, DNA polymerases, ligase
Which of the following components is required for DNA replication?
RNA primer
The removal of the RNA primer and addition of DNA nucleotides to the 3' end of Okazaki fragments in its place is carried out by _____.
DNA polymerase I
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 _____.
topoisomerase
Once the DNA at the replication fork is unwound by helicases, what prevents the two strands from coming back together to re-form a double helix?
Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming.
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
The incorporation of an incorrect base into the DNA during replication _____
can be repaired by the mismatch repair system
Which set of enzymes is involved in nucleotide excision repair?
nuclease, DNA polymerase, and ligase
unlike prokaryotic DNA replication, replication of eukaryotic chromosomes ___
cannot be completed by DNA polymerase
Telomeres _____.
get shorter with continued cell division

is an enzyme that lengthens telomeres
Which of the following best illustrates the importance of altered DNA nucleotides in evolutionary processes?
In a temporally variable environment, a population of bacteria with an elevated rate in replication error can have a selective advantage over other populations with lower rates in replication error.
What is the major difference between bacterial chromosomes and eukaryotic chromosomes?
Bacteria have a single circular chromosome whereas eukaryotes have several linear chromosomes.
Put the following DNA-containing entities in order according to the amount of DNA found in their genomes.
virus, bacteria, eukaryote
The "beads on a string" seen in interphase chromatin are _____
nucleosomes
DNA is the genetic material of a virus called
phage T2
parts of the phage
The phage, which infects E. coli, consists of a head, sheath, tail, and base plate made of different proteins. DNA is packaged within the head of the virus.
Because genetic material is passed on from parent to offspring, Hershey and Chase concluded that
DNA had to be the genetic material of T2. Their results helped convince the scientific community that DNA was the hereditary material.
DNA and RNA are nucleic acids
polymers made of subunits called nucleotides.
Nucleotide structure
nitrogeneous base, sugar, and phosphate group
One difference between DNA and RNA is the type of sugar their nucleotides contain
DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. Ribose has one more oxygen atom than deoxyribose.
Three of the four bases are the same in DNA and RNA
adenine, guanine, and cytosine. The fourth base in DNA is thymine. In RNA it is uracil.
the synthesis of a new strand begins when an enzyme called ______ attaches and synthesizes a short RNA strand that is complementary to one of the DNA strands. This piece of RNA is a _____
primase

primer
In his work with pneumonia-causing bacteria and mice, Griffith found that
some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
DNA polymerase can join new nucleotides only to the 39 end of a growing strand.
DNA polymerase can join new nucleotides only to the 39 end of a growing strand.
A + G = C + T
The elongation of the leading strand during DNA synthesis
depends on the action of DNA polymerase.
In a nucleosome, the DNA is wrapped around
histones.
E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?
one low-density and one intermediate-density band
A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
DNA Ligase
chromatin



euchromatin





Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.
The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.


The less condensed form of eukaryotic chromatin that is available for transcription.



heterochromatin