genetics practice questions exam 2
an origin of replication generally has __ replication forks
2
in typical human cell DNA polymerase replicates about ___ nucleotides per second
50
packaging into nucleosomes condenses naked DNA bout
7 fold
33. The first level of compaction of DNA consists of: A) DNA winding around histones to form small nucleosomes. B) tight coiling of DNA with nucleosomes into higher order structures. C) high level compaction into metaphase-type chromosomes. D) histone, DNA, and nonhistone covalent bonding.
A
39. The total compaction of DNA as seen in metaphase chromosomes is approximately ______ fold. A) 10,000 B) 50,000 C) 100,000 D) 40
A
25. Despite selection against chromosomal variations: A) related species almost always have the same karyotype. B) related species almost always have a different karyotype. C) closely related species diverge by many chromosomal rearrangements. D) distantly related species diverge by only a few chromosomal rearrangements.
B
25. The enzyme that some organisms use to replicate DNA at the 5' ends of chromosomes is called: A) DNA polymerase. B) telomerase. C) DNA ligase. D) replicase.
B
39. Which of the following does not usually show a problem during meiosis? A) translocation heterozygotes B) translocation homozygotes C) paracentric inversion D) pericentric inversion
B
50. Which of the following is not an aneuploidy? A) monosomy B) tetraploid C) trisomy D) tetrasomy
B
55. In yeast chromosomes, centromeres: A) help distinguish one chromosome from another. B) are closely related in sequence. C) are only 10-15 bp long. D) play various roles in chromosome segregation.
B
63. From DNA research, sites of transcription and therefore most of the genes along the length of the chromosome appear to be found in: A) heterochromatin. B) euchromatin. C) constitutive heterochromatin. D) centromeric regions.
B
24. Karyotypes generally remain constant within a species because: A) rearrangements occur frequently. B) changes in chromosome number occur infrequently. C) genetic instabilities produced by genomic changes usually are at a selective disadvantage. D) genetic imbalances are often at a selective advantage.
C
30. Histones and DNA have a strong attraction for each other because: A) DNA is positively charged and histones are negatively charged. B) both DNA and proteins are hydrophobic. C) DNA is negatively charged and histones are positively charged. D) like substances share common charges. E) none of the above
C
35. Inversions may be hard to detect because they: A) never visibly change chromosome banding patterns. B) increase recombination in heterozygotes. C) do not usually cause an abnormal phenotype. D) normally are removed immediately in natural populations.
C
52. In DNA, most satellite sequences are found in: A) chromosome arms. B) telomeres. C) centromeres. D) spaces around the dark bands. E) none of the above
C
55. Which of the following is not an example of a euploid condition? A) triploidy B) diploidy C) Down syndrome D) tetraploidy
C
18. DNA is localized mainly in the: A) cell membrane. B) endoplasmic reticulum. C) vacuoles. D) chromosomes. E) none of the above
D
21. Sometimes a piece of one chromosome attaches to another chromosome. This is known as a(n): A) inversion B) duplication C) deletion D) translocation E) none of the above
D
31. Which of the following is not a role ascribed to nonhistone proteins found in chromatin? A) structural B) replication C) chromosome segregation D) nucleosome packers
D
32. Histones appear to have a singular role in the packaging of DNA. The nonhistone proteins in chromatin have which of the following functions? A) different functions for different tissues, such as tissue-specific transcription factors B) activity at different moments in the life cycle C) centromere function activity D) all of the above
D
36. In DNA, the 300Å fiber is formed into structural loops. Responsibility for this function appears to lie with: A) histone H4. B) nucleosomase. C) histone H1. D) certain nonhistone proteins.
D
42. Translocations can help: A) determine linkage groups. B) aid in the diagnosis and treatment of certain cancers. C) map important genes. D) all of the above
D
43. Down Syndrome can result from: A) three copies of chromosome 21. B) a translocation of a part of chromosome 21. C) a reciprocal translocation between any two autosomes. D) a and b E) a, b, and c
D
48. Which of the following is not true about DNA polymerase? A) It cannot begin the 5' end of a new strand without a primer. B) It can only travel in the 5'-to-3' direction. C) It can reconstruct the 3' end of each newly made DNA strand. D) It can replace RNA primer with DNA at the 5' end.
D
53. Turner syndrome, XO, is a sex chromosome aneuploidy. Of the effects listed below, which one is not usually seen in this syndrome? A) unusually short stature B) infertility C) skeletal abnormalities D) unusually long limbs
D
54. During mitosis, kinetochores develop during: A) telophase. B) anaphase. C) metaphase. D) prophase.
D
An inversion may result from: A) a half-circle rotation of a chromosomal region after two double-strand breaks in a chromosome's DNA. B) the action of a transposable element. C) a crossover between DNA sequences present in two positions on same chromosome in inverted orientation. D) all of the above
D
In higher organisms, using genetic analysis is usually difficult to distinguish small deletions in one gene from: A heterozygotes. B small duplications. C monosomies. D point mutations.
D
Which of the following does not happen when an intragenic inversion occurs? A One part of the gene is relocated to a distant region of the chromosome. B One part of the gene stays at its original site. C Homozygotes for the inversion do not survive. D The gene's function is not disrupted.
D
avery, macleod and McCarthy's experiments
DNA=molecule of heredity
51. The two chromatids of each replicated chromosome must separate from one another and segregate during: A) mitosis. B) meiosis I. C) meiosis II. D) both a and b E) both a and c
E
Sometimes a part of the genome moves from chromosome to chromosome. This is known generally as a(n): A) inversion B) duplication C) deletion D) translocation E) transposable element
E
during the DNA replication process RNA primers are removed and replaced with DNA why is it important that it is replaced
RNA is more unstable than DNA which could be easily degraded. and dna must be present so that the next round of replication may proceed.
20. The polarity of DNA synthesis is: A) 5'3'. B) 3'5'. C) 5'2'. D) 2'5'. E) none of the above
a
21. In the Hershey and Chase experiment designed to determine the molecule of heredity, what was radiolabeled with 35S? A) protein B) DNA C) RNA D) rRNA E) none of the above
a
30. During early interphase the state of the DNA can be described as: A) a single continuous linear double helix. B) a double helix replicated semiconservatively. C) a double helix replicated conservatively. D) single-stranded DNA. E) none of the above
a
32. The step in DNA replication in which the replication proteins open up the double helix and prepare for complementary base pairing is called: A) initiation. B) elongation. C) termination. D) translation. E) translocation.
a
44. Recombination involves the breakage and reunion of DNA molecules from: A) homologous nonsister chromatids. B) homologous sister chromatids. C) heterologous nonsister chromatids. D) heterologous sister chromatids. E) none of the above
a
47. If 35% of the bases in a region of the mouse genome are cytosine, what percentage in that region are adenine? A) 15% B) 20% C) 30% D) 35% E) none of the above
a
why do inversions act as cross over supressors
an inversion loop cannot recombine
16. The molecule of heredity is: A) RNA. B) DNA. C) protein. D) carbohydrate. E) none of the above
b
22. The ratio of _____ is 1:1. A) guanine to adenine B) adenine to thymine C) cytosine to adenine D) uracil to cytosine E) none of the above
b
23. X-ray data showed that the spacing between repeating units along the axis of the DNA helix is: A) 2.0 angstroms. B) 3.4 angstroms. C) 20 angstroms. D) 34 angstroms. E) none of the above
b
28. DNA replication occurs through a _________process. A) conservative B) semiconservative C) dispersive D) transferal E) none of the above
b
31. During the S phase of interphase, the state of the DNA can be described as: A) a single continuous linear double helix. B) a double helix replicated semiconservatively. C) a double helix replicated conservatively. D) a triple helix replicated semiconservatively. E) none of the above
b
33. The step in DNA replication in which the proteins connect the correct sequence of nucleotides into a continuous new strand is called: A) initiation. B) elongation. C) termination. D) translation. E) translocation.
b
51. Occasionally, a loss of function mutation may occur in the telomerase enzyme in a cell. What is likely to be the result of this mutation on the DNA in the cell over the course of several rounds of mitosis? A) Chromosome length will gradually increase. B) Chromosome length will gradually decrease. C) Chromosome length will stay constant. D) Chromosomes will fail to dissociate after replication. E) None of the above
b
a virus that infects bacteria cells is called _______
bacteriophage
design an experiment that utilizes suggestive physical evident to test the hypothesis that during recombination DNA molecules break and rejoin
bacteriophage previously grown in either heavy or light isotopes can be used to track breakage by infection of bacteria and gradient centerfugation. banding at densities intermediate to the heavy and light phage dna indicates breakage and rejoining.
Watson and crick's experiment
basic structure of dna
discuss the roles proteins play in reproducing chromatin structure
before dna synthesis can occur the chromatin fiber must unwind. newly formed DNA must associate with histones. they synthesis and transport of histones must be coordinated with DNA synthesis since the DNA becomes incorporated into nucleosomes soon after formation. The nucleosomal DNA must interact in specific ways with a variety of proteins to compact in the same pattern as before
discuss the several effects that translocations and inversions have in common
both change genomic position without affecting the total amount of DNA. if a breakpoint of either one is within a gene, the gene function may be altered or lost. both may produce genetically imbalanced gametes that may negatively affect a zygote or developing embryo. both reduce viable progeny and heterozygotes.
17. The four subunits which compose DNA are called: A) phosphodiesters. B) proteins. C) nucleotides. D) nucleosides. E) polymers.
c
20. In general, which of the following usually has a greater chance of lethality than the others? A) inversion B) duplication C) deletion D) translocation
c
25. ________ bonds are responsible for the chemical affinity between A and T (or G and C) nucleotides. A) Ionic B) Covalent C) Hydrogen D) Electro-ionic E) none of the above
c
29. During complementary base pairing, enzymes join the base's nucleotide to the preceding nucleotide by a __________bond. A) hydrogen B) ionic C) phosphodiester D) electrostatic E) none of the above
c
34. The step in DNA replication in which two replication forks moving in opposite directions may meet is called: A) initiation. B) elongation. C) termination. D) translation. E) translocation.
c
41. The process of _________ is extremely important in generating genetic diversity. A) translation B) transcription C) recombination D) transformation E) none of the above
c
43. Recombination occurs during meiotic ________. A) anaphase B) interphase C) prophase D) metaphase E) none of the above
c
46. What radiolabeled substance did Hershey and Chase use to label the protein component of the bacteriophage in their study to determine whether protein or DNA was necessary for phage production? A) nitrogen B) carbon C) sulfur D) phosphorous E) iodide
c
explain the possible effects that a transposable element may have on a gene
can affect the gene expression and alter the phenotype. depends on what the element is and where the insertion point is. it may cause a frame shift or cause a stop codon to be introduced.
chromosome regions that remain condensed in heterochromatin at most times in all cells are known as ________ heterochromatin
constitutive
_____ made of repetitious DNA that is late to replicate and is transcriptionally inactive
constitutive heterochromatin
alternative resolutions of the holiday intermediate are responsible for whether or not ____________ occurs
crossing over or gene conversion
24. X-ray data showed that the DNA helix undergoes one complete turn every: A) 2.0 angstroms. B) 3.4 angstroms. C) 20 angstroms. D) 34 angstroms. E) none of the above
d
39. Eukaryotic chromosomes have evolved special structures at the ends of chromosomes to ensure the replication of the two ends of linear chromosomes. These structures are called: A) methylases. B) capping proteins. C) ligases. D) telomeres. E) single-stranded biding proteins.
d
53. Hershey and Chase relied on ________ to physically separate the infected bacterial cells from the phage ghosts. A) radioactivity B) gel filtration C) ion exchange D) centrifugation E) none of the above
d
a decrease of genetic material in the genome
deletion
how do deletions and duplications contribute to evolution
deletions-may move a coding sequence to the next promoter or other regulatory element of an adjacent gene may allow expression of a protein at a important time during expression which could benefit the organism. duplications-if one copy maintains the original function the other may have a new job which would be related to the original
miescher's experiment
discovery of "nuclein"
a change in the genome whereby new material is added
duplication
15. Which of the following is not true of DNA? A) It is acidic. B) It contains deoxyribose. C) It is found in cell nuclei. D) It contains phosphate. E) It contains proteins.
e
19. Each nucleotide of DNA is made up of: A) a deoxyribose sugar. B) a nitrogenous base. C) a phosphate. D) a and b only. E) all of the above
e
38. In eukaryotic cells, replication proceeds from ____ origin(s) of replication. A) no B) one C) two D) several E) many
e
54. Meselson and Stahl relied on equilibrium density gradient centrifugation in a _______ solution to resolve the DNA containing 14N from the DNA containing 15N. A) radiolabeled phosphate B) calcium chloride C) radiolabeled nitrogen D) sodium acetate E) cesium chloride
e
holiday's experiment
early recombination models
regions of chromosomes that are heterochromatic in some cells and euchromatic in other cells of the same organism are _______ heterochromatin
facultative
Hershey and chase's experiment
famous phage blender experiment
briefly describe the role of an initiator protein
first protein to bind to the origin of replication and attracts helicase which is unable to unwind the region surrounding the origin
Griffith found that smooth S. pneumonia have a poly saccharide capsule and rough do not. only S cause infection. describe how he demonstrated transformation using live R form and heat killed S form bacteria
heat killed S does not yield infection, R does not yield infection, when S heat killed and R live are injected together infection does occur. R had been transformed by S
cells express their genes mainly during ____ when their chromosomes have decondensed or decompacted
interphase
a change in the genetic material where a DNA sequence changes direction
inversion
the type of chromosomal rearrangement which reorganizes the DNA sequence within one chromosome is known as a
inversion
very large deletions are visible at the relatively low resolution of a ______ showing up as the loss of one or more bands from a chromosome
karyotype
the _______ strand is synthesized continuously during replication
leading
Why are triploid organisms almost always sterile
meiosis produces mostly unbalanced gametes. most gametes will be aberrant and will have a reduced chance of producing viable offspring.
explain the mechanism by which aneuploidy occurs
meiotic nondisjunction in meiosis 1 or 2. if homologs do not separate all gametes produced will have an error. two of the gametes will contain both homologs and two will have none. when fertilization of these occurs aneuploidy occurs. half will be trisomic and half will be monosomic. if it happens during meiosis 2 than two will be normal and two will be abnormal.
the most rudimentary DNA packaging unit which involves four types of histones is the
nucleosome
chargaff's experiment
nucleotide ratios of dna
the discontinuous lagging strand on a replication fork consists of _____ fragments that are later ligated together to form one strand of DNA
okazaki
how is a nucleosome constructed from DNA and histone proteins
on an electron micrograph the chromatin fibers resemble beads on a string. the string is dna and the beads are histone proteins. DNA wraps twice around the histone core to form chromatin fiber's beads.
a ______ bond joins one nucleotide together in the DNA polymer
phosphodiester
describe ways the telomeres are critical to chromosome function
prevent shortening during replications which would dismantle the genes. maintain integrity of the chromosomal ends. broken chromosomes without telomeres are defective by the cellular DNA repair machinery. the repair will put broken ends back together. if not they can cause chromosome fusion or degradation entirely
the protein _____ is needed to lay down a segment of RNA complementary to the DNA before replication can begin
primase
explain the differenct between chromosomal rearrangements and changes in chromosome number
rearrangements reorganize the DNA sequences within one or more chromosomes. ex. deletion, duplication, inversion, translocation changes in chromosome number involve losses or gains of entire chromosomes or sets of chromosomes ex. aneuploidy: monosomy, trisomy, monoploidy, polyploidy
type of large scale mutation in which parts of two different chromosomes trade places is a _________
reciprocal translocation
_____ a genetic element that behaves as autonomous unit during DNA replication
replicon
meselson and radding's experiments
revised recombination models
centromeres are contained within blocks of repetitive simple noncoding sequences known as ______DNA
satellite
meselson and stahl
semiconservative replication
when repeats of a region lie adjacent to each other they are called _______ duplications
tandem
in many human tumor cells abnormal activation of the _____ gene seems to bestow the capacity to divide infinitely
telomerase
describe the relationship between chromatin structure and gene function in eukaryotic chromosomes
the compaction of chromosomes makes dna inaccessible to the gene function. the compaction makes it so that proteins cant initiate gene expression. this is greatest at metaphase and anaphase which stops gene transcription at these times. decompaction precedes gene expression, this depends on a network of dna protein interactions which modifies the density of chromatin packaging.
when meselson and stahl performed the experiment that showed that replication is a semiconservative process they used E. coli and isotopes of nitrogen. what would the results have been if dna was replicated conservatively
the first generation would have 2 bands, the second generation would have the same resulting pattern with no hybrid pattern ever revealed.
if you're mapping traits of an organism how would it be effected if the organism has a deletion
the mapping distance will be smaller than it should be
if you do a FISH on different organisms of the same animal and see that a specific gene is on a different chromosome for each of them how would you interpret this
the unusual sequence is a transposon and your new phenotype arose via a disruption of its gene by the transposon
the largest class of nonhistone proteins foster or regulate _______ and RNA processing during gene expression
transcription
Griffith's experiment
transformation (R and S strains)
a piece of chromosome attaches to another chromosome
translocation
a piece of genetic material that moves from place to place in the genome
transposable element
transformation in bacteria results from
uptake of foreign DNA
franklin and wilkins experiment
x ray structure of dna
