Past Exam 2017 Flashcards by Marissa Brosseau

The 4 subunits that compose DNA are

Nucleotides

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In the Hershey and Chase experiment designed to determine molecule of heredity, what was radiolabelled with 35S

Protein

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X-ray data showed that the spacing between repeating units along the axis of the DNA helix is

3.4 angstroms

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_______ bonds are responsible for the chemical affinity between A and T (or G and C)

Hydrogen

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________-form DNA spirals to the right and is the major form of naturally occurring DNA molecules

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DNA replication occurs through a _______ process

semiconservative

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During early interphase, the state of the DNA can be described as

A single continuous linear double helix

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The step in DNA replication in which the replication proteins open up the double helix and prepare for complementary base-pairing is called

Initiation

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The step in DNA replication in which two replication forks moving in opposite directions may meet is called

Termination

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The protein that progressively unwinds DNA ahead of each replication fork is called

Helicase

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What radiolabelled 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?

Sulfur

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Meselson and Stahl relied on equilibrium density gradient centrifugation in a ______ solution to resolve the DNA containing 14N from the DNA containing 15N

Cesium chloride

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The energy for DNA synthesis comes most directly from

dNTP

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If chromosomal DNA were single stranded, which of the following would be most reduced compared to a double stranded molecule?

Information fidelity (the consistency of sequence between generations)

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The enzyme that some organism use to replicate DNA at the 5’ ends of chromosomes is called

telomerase

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The chromosome can be considered a dynamic organelle for _________ of DNA

All of the above
(expression, segregation, replication, packaging)

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By weight the chromatin consists roughly of

1/3 DNA, 1/3 histones and 1/3 nonhistones

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Without __________ regions on the DNA during recombination, gene conversion could not occur

heteroduplex

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The first level of compaction of DNA consists of

DNA winding around histones to form small nucleosomes

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Nucleosomal chromatin, with a diameter of 100A, supercoils into a 300A superhelix. The histone that appears to be responsible for this compaction is

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At what stage of mitosis do we first see a chromosome that is compacted 250-fold over the 40-fold compacted 300A fibre

Metaphase

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The total compaction of DNA as seen in metaphase chromosomes is approx. _______ fold

10,000

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With regard to the typical human cell, which of the following appears to be true

There are multiple origins of replication that function simultaneously

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The 10,000 origins of replication in mammalian calls suggests that concerning origin of replication there is

at least one per loop of DNA

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Which of the following is not true about DNA polymerase

It can replace RNA primer with DNA at the 5' end

The two chromatids of each replicated chromosome must separate from one another and segregate during

Both A and C (mitosis and meiosis 2)

One of the functions of a centromere is to contribute to proper chromosome segregation. The other function is to

hold sister chromatids together

During mitosis, kinetochores develop during

prophase

In higher eukaryotes, kinetochores attach to

multiple spindle fibers

During development, an XX female embryo will form one of the X chromosomes in each cell into a Barr body. This usually occurs

about 2 weeks after zygote formation

recombination occurs during meiotic

prophase

The nicking of DNA that initiates recombination during mitosis may be due to all but

instruction from normal cell-cycle program

Which of the following statements about the double strand break-repair model is true?

Recombination is initiated by the double strand breaks on each of the two sister chromatids

which of these is required for the first strand invasion in the double-strand break repair model?

3' single stand tails on one sister chromatid

Which of the following enzymes is not required for recombination in the double-strand break repair model

Double strand recombinase

In the usual flow of genetics information (often called the Central Dogma), which of the following best represents the expression of genes?

DNA-RNA-Protein

The scientists credited with postulating the basis for the genetic code are

Watson and Crick

which of these is NOT a character of the genetic code

There are the same number of codons as there are amino acids

There are __________ usually found in the genetic code

1 start codon and 3 stop codons

Which of these terms is NOT a stop codon or a nickname for a stop codon

emerald

Which of these is NOT a step in transcription

replication

The (expressed) sequences within mRNA that code for gene products are called

exons

A(n) _________ consists of proteins and small nuclear RNAs forming discrete particles that mediate splicing

splicesome

Transcription occurs in the _______ and translation occurs in the _________ of eukaryotic cells

Nucleous ; cytoplasm

In the modification of eukaryotic mRNA, a "cap" consisting of an _________ and a tail consisting of ______ are usually added to the transcript

methyl groups, multiple adenines

Ribosomes are composed of

rRNA and protein

Aminoacyl-tRNA sythetase is the enzyme that

Adds the appropriate amino acid to an uncharged tRNA

A bacterial (prokaryotic) ribosome is composed of _______ subunits

30s and 50s

Which of these processes are coupled (linked) in prokaryotes but NOT in eukaryotes

transcription and translation

A mutation that changes a codon sequence, and subsequently changes the amino acid that should have been placed at that point in the polypeptide chain, is called a

Missense mutation

A mutation that occurs when a base is inserted into or deleted from a DNA sequence, completely alternating the subsequent amino acid sequence is called a

Frameshift mutation

A tRNA that recognizes a nonsense codon and inserts an amino acid where protein synthesis should have stopped is called a

Suppressor tRNA

mutations that abolish the function encoded by wild-type allele are known as

Null mutations

A neomorphic mutation results in an allele that

Produces novel proteins or cause inappropriate expression resulting in a new phenotype

Assume that for a given gene a mutation creates an allele that functions as dominant negative. The gene codes for a protein that forms a trimer within the cell. If at lease of the subunits has the mutant structure the entire process is inactivated. For a heterozygous individual, what percent of the trimers present in the cell will be inactive

12.5%

As compared to subunit vaccines, what is the main advantage of "killed whole virus" HIV vaccine under development in Canada

jknk

What would happen if all of the snRNAs were removed from a cell

The term mutation refers to

A heritable change in the DNA of a cell

Replacing a thymine nucleotide with a guanine is an example of a

transversion

Assume that a wild-type sequence is 5'AGCCTAC3'. indicate the sequence that might be produced by a transversion

5'ATCCTAC3'

Assume that the mutation rate for a given gene is 5x10^-6 mutations per gene per generation. For that gene how many mutations would be expected if 10 million sperms are examined

Consider the following results. When 50 million sperms were examined for a specific mutation, 100 mutations were found. Indicate the mutation rate for that gene

2 x 10^-6

The results of the Luria-Delbruck fluctuation experiment indicated that

Bacteria become resistant to phage by random spontaneous mutations

The hydrolysis of a purine base from the deoxyribose-phophate backbone is called

Depurinination

UV light is a mutagen that can cause

Thymine dimers

The heritable disorder fragile X syndrome, a major cause of mental retardation, is caused by

Duplication of multiple 3- nucleotide repeats

The duplication of the triplet sequence CGG resulting in elongation or breakage of the X chromosome is termed

Fragile X syndrome

If a base analogue such as 5-bromouracil is used as a mutagen, how many generations will be required to mutate the codon for proline (CCC) into the codon for alanine (GCC)

It will not occur

Interacting agents such ethidium bromide function as a mutagen

Assuming that in the organism under study, the DNA polymerase has an error rate of 1 mistake in every 10^6 bases copied. However, the overall mutation rate is much lower. This is most likely because

Repair mechanisms correct errors made by the polymerase

The genetic condition Xeroderma pigmentosum, which can lead to skin cancer, results from

Inability to correct UV induced dimers

The consequences to a bacterial cell of a mutation that inactivated the enzyme that methylates the A of the sequence GATC in newly made DNA would be

Failure to distinguish old and new DNA during mismatch repair

In the Ames test for mutagenicity, rat liver enzymes are included with the compound under tests because

Rat liver enzymes may modify or break down some compounds

The Ames test for mutagenicity is useful to identify potential carcinogens because

Mutagens that affect bacterial DNA are likely to cause human mutation

Assume a researcher is studying coat colour in voles. Three stains of white vole have been isolated: milky, blanc, and weiss. White is a recessive train in each strain. Homozygous white voles are obtained for each strain. Consider the following crosses: milky x blanc = all white milky x weiss = brown (wild-type) blanc x weiss = brown (wild-type) The conclusion most consistent with these results is

In the human genetic disorder Alkaptonuria, urine turns black because of the presence of homogentisic acid and in individuals with the trait. this is due to

Failure of individuals with Alkaptonuria to manufacture enzymes involved in the breakdown of homogentisic acid

Indicate the false statement regarding amino acids

all correct

Choose the condition that involves a defect in an enzyme pathway

The condition sickle-cell amaemia is due to

Substitution of an amino acid

Though sickle-cell anaemia is frequently lethal for individuals who are homozygous for the sickle-call allele, natural selection seems to have maintained that allele in certain geographic locations. A likely explination for this observation is that

Individuals who are heterozygous for the sickle-cell allele are protected from malaria

The structure of a protein that involves the interaction between two distinct polypeptide chains is

Quaternary structure

The photoreceptor protein rhodopsin

is found in rod cells and is sensitive to weak light at many wavelengths

Red green colour blindness is more common in males than females because

Both the red and the green pigment genes are on the X chromosome

Which of the following is used in site-directed mutagenesis

Synthetic oligonucleotide

How are somatic mutations different from germline mutations

Only germline mutations are heritable

Which of the following is not considered a chromosomal rearrangement

Replication

Karyotypes generally remain constant within a species bases

Genetic instabilities produced by genomic changes usually are at a selective disadvantage

In higher organisms, it is usually difficult to distinguish with genetic analysis small deletions in one gene from

point mutations

During the pairing of homologues in prophase of meiosis 1, the region of a normal, nondeleted chromosome that has nothing with which to recombine forms a so-called

Deletion loop

Which of the following does not happen when an intragenic inversion occurs

The genes function remains unaffected

Robertsonian translocation results from which of the following

Breaks at or near the centromeres of two acrocentric chromosomes followed by the reciprocal exchange of broken parts

Which of the following would be most helpful in mapping the genes that cause down syndrome

In terms of evolution, what is the most frequent outcome of repeated duplications of different segments of a species genome

Gene families

In Drosophila, a gynandroporph, which is composed of equal parts of a male and female tissue, results from

An XX female losing one X chromosome during the first mitotic division after fertilization

Which of the following causes yellow corn kernals to gain red spots

Past Exam 2017 Flashcards

(95 cards)