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Exam 3 Dr. Gee

Bodnar et al. (1998) used telomerase to extend the life span of normal human cells. Telomere shortening puts a limit on the number of times a cell can divide. How might adding telomerase affect cellular aging?

) Telomerase ensures that the ends of the chromosomes are accurately replicated and eliminates telomere shortening.

Marfan syndrome results from a defect in a single gene FBN1. Individuals with Marfan syndrome exhibit a wide array of phenotypic effects such as increased height, disproportionately long limbs and fingers, an abnormally shaped chest and potentially severe heart problems. The FBN1 gene influences many traits and is therefore ___________.

pleiotropic

A cross between pure-breeding chicken lines with rose combs and pea combs produces offspring all having a new phenotype, walnut comb. If two walnut comb chickens are mated, the offspring will have the following phenotypes: walnut comb, rose comb, pea comb, and a new phenotype called single comb. Which of the following statements best explains this result?

The alleles of two genes are interacting to produce the different phenotypes.

Which of the following statements is true of DNA synthesis?

DNA polymerase requires a single-stranded template plus a primer to synthesize DNA.

Put the following steps of DNA replication in chronological order.

hydrogen bonds between base pairs of antiparallel strands are broken.
Single-stranded binding proteins attach to DNA strands.
Primase binds to the site of origin.
An RNA primer is created.
DNA polymerase binds to the template strand.

During meiosis, Sister chromatids separate during ________.

anaphase II.

What is a major difference between meiosis II and mitosis?

Meiosis II takes place in a haploid cell, while mitosis takes place in diploid cells.

Which of the following cells do not have active telomerase activity?

most normal somatic cells

Imagine that you are a researcher trying to develop a gene therapy for XP patients. The best gene to incorporate into the skin cells of these patients would be a gene _____.

that would increase the production of DNA repair proteins

What is a major difference between mitosis and meiosis I?

Sister chromatids separate in mitosis, and homologues separate in meiosis I.

Refer to the Figure on the right. What bases will be added to the primer as DNA replication proceeds? The bases should appear in the order that they will be added starting at the 5' end of the new strand.

A, G, A, C, G, A, C

What is the difference between the leading strand and the lagging strand in DNA replication?

The leading strand is synthesized continuously in the 5'→3' direction, while the lagging strand is synthesized discontinuously in the 5'→3' direction.

Refer to Figure on the right. A branched metabolic pathway synthesizes two related amino acids (D and F). If there is a genetic defect, resulting in a nonfunctional enzyme (3), how could you ensure that adequate amounts of the amino acid F are synthesized?

Supplement with intermediate E

Refer to Figure above you used to answer question 13. In the branched metabolic pathway, if enzyme 3 is defective and the amount of each enzyme is constant, you might expect to see an increase in the amount of which intermediate/product?

D

In the Morse code, a series of dots and dashes code for letters of the alphabet. How is this analogous to the genetic code?

The bases of DNA code for the more complex amino acid sequence of the various proteins found in cells.

The bases of DNA code for the more complex amino acid sequence of the various proteins found in cells.

pass the G2 checkpoint

In 1985 Hassold and Chiu found that the likelihood of miscarriage increased with maternal age. What is the most likely explanation for the relationship between age and miscarriage?

Ova are arrested in meiosis until ovulation. As a result, completion of meiosis in the older woman is more likely to result in aneuploidy or other chromosomal abnormalities.

For cells to divide more rapidly, increased production would likely be required of each of the following proteins except ________. (Hint: Which one is a tumor suppressor?)

p53

Centromeres split and sister chromosomes migrate to opposite poles in _____.

anaphase II

In the process of transcription, _____.

RNA is synthesized

Codons, the three base sequences that code for specific amino acids, are part of _____.

mRNA

If meiosis produces haploid cells, how is the diploid number restored for those organisms that spend most of their life cycle in the diploid state?

fertilization

How might a single base substitution in the sequence of a gene affect the amino acid sequence of a protein encoded by the gene, and why?

Only a single amino acid could change, because the reading frame is unaffected.

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.

A certain species of animal has six pairs of chromosomes. How many individual chromosomes do the nuclei of these animal's somatic cells have during G2 phase?

24

Mitotic spindle fibers are composed of what cellular structures?

microtubules

Taxol is a drug that stabilizes microtubules in animal cells and prevents them from depolymerizing. Consequently cells treated with Taxol fail to complete mitosis. What event during the subphases of mitosis is most likely to be inhibited by this drug?

movement of the sister chromatids to their respective poles

Which of the following statements concerning crossing over is true?

Chromosomes that result from crossing over have a mixture of maternal and paternal alleles

The consequence of E2F activation is that

cells would immediately enter the S phase

The statement, DNA → RNA → Proteins, _____.

) has become known as the central dogma

Genotype is to _____ as phenotype is to _____.

DNA base sequence; amino acid sequence

If the prokaryotic RNA polymerase is missing its _____ then transcription initiation would not occur but elongation could.

sigma factor

A cross between Ttrr and TtRR snapdragon plants where T is the dominant allele for plant height (tall), t is the recessive allele for plant height (dwarf), R is the dominant allele for flower color (red), and r is the recessive allele for flower color (white) would result in what proportion of offspring with pink flowers on dwarf plants?

1/4

. David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the -10 box and the -35 box). What is the function of these two regions of the promoter?

They bind the sigma factor subunit that is associated with RNA polymerase

. Put the following events of transcription in chronological order.
1. Sigma binds to the promoter region.
2. The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands.
3. Sigma binds to RNA polymerase.
4. Sigma is released.
5. Transcription begins.

3, 1, 2, 5, 4

. The first gap in the cell cycle (G1) corresponds to ________.

normal growth and functioning.

man who carries an allele of an X-linked gene will pass it on to ________.

all of his daughters

Metaphase occurs prior to the splitting of centromeres. It is characterized by ________.

aligning of chromosomes on the equator

If an individual with type O blood mates with an individual with type AB blood, what are the possible blood types (phenotypes) of their offspring?

A and B

. Nerve cells lose their ability to undergo mitosis. Instead, they are permanently stuck in ________.

G0

If a heterozygous type A (blood type) man has a child with a heterozygous type B woman, what are the possible blood types of the offspring, regardless of whether the child is male or female?

AB, A, B, and O

A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision whose father is color blind marries a color-blind male. What is the probability that this couple's first son will be color blind?

) 50%

A primary transcript in the nucleus of a eukaryotic cell is _____ the functional mRNA, while a primary transcript in a prokaryotic cell is _____ the functional mRNA.

larger than; the same size as

Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis?
A) Both cyclin and Cdk subunits are completely degraded.

Cyclin is degraded; the concentration of cyclin-dependent kinase remains unchanged, but without cyclin, MPF is not formed.

Which early theory, proposed by Charles Darwin, involved the shedding of gemmules by somatic cells and the subsequent traveling of these gemmules through the bloodstream to the reproductive tissue to provide genetic info to gametes?

pangenesis

The M-phase checkpoint is designed to make sure all chromosomes are attached to the mitotic spindle. If this fails to happen, in which stage of mitosis would the cells be most likely to arrest?

metaphase

There are 61 codons that each specify the addition of a specific amino acid, and three stop codons for which there is no corresponding amino acid. However, there are only about 40 tRNA molecules, representing 40 anticodons. How is that possible?

An anticodon forms hydrogen bonds with the codon; it must match the first two bases of the codon, but is less specific with respect to the third base, i.e. the wobble hypothesis

Nondisjuction of chromosomes results in _______________.

aneuploidy

A mutation that results in premature termination of translation _____.

is a nonsense mutation

What is a key difference between benign tumors and metastatic tumors?

metastatic tumors are invasive

One of the causes of cancer is the mutation of genes that encode proteins in the biochemical pathway regulated by PDGF, a growth factor. How could such mutations cause cancer?

Cancer could result if the mutations caused the biochemical pathway to become permanently active.

. Suppose two AaBbCc individuals are mated. Assuming that the genes are not linked, what fraction of the offspring are expected to be homozygous recessive for the four traits?

1/64

A mutation that results in a base substitution, but does not change the amino acid coded for, is a _____.

is a silent mutation

DNA is synthesized through a process known as _____.

semiconservative replication

Refer to the figure on the right. The mRNA is smaller than the length of the DNA that codes for it because _____.

transcriptional modification removes the introns

Which of the following does not occur in post-transcriptional modifications of eukaryotic mRNAs?

RNA polymerase termination

Which of the following occurs in prokaryotes, but not eukaryotes?

concurrent (occurs almost at the same time) transcription and translation

What molecule/feature ensures that the correct amino acid is added with reading of a specific codon during translation?

the anticodon of a properly formed aminoacyl tRNA

According to the wobble hypothesis _____.

More than one codon specifies for an amino acid and they all have the same nucleotides in the first two positions.

Hereditary nonpolyposis colorectal cancer (HNPCC) is an inherited disorder. The genetic defect identified is an error in the mismatch repair mechanism. Which of the following would be an expected result of this mutation?

decreased ability to repair certain DNA mutations

A mutation that results in premature termination of translation due to the introduction of a stop codon_____.

is a nonsense mutation

Refer to the Figure on the right. What is the function of the AGU on the bottom stem-loop of the tRNA?

It base pairs with the codon of mRNA

to Figure on the right. What is the function of the exposed single stranded ACC sequence at the 3' end?

It attaches to the amino acid.

If DNA repair mechanisms fail, what is the result?

A) a mutation can be introduced
B) a defective enzyme may be produced
C) cancer may result
D) All of the above can result from the failure of DNA repair mechanisms.

The lack of organelles in bacteria impacts transcription and translation in which way?

Transcription and translation can occur simultaneously

Which of the following is true about the evolution of the genetic code?

The existing genetic code is structured in a way that efficiently minimizes the phenotypic effects of small changes in DNA and errors during translation.

What happens when an individual has an odd number of chromosome sets (e.g., triploidy)?

Their offspring are often sterile.

Homologous chromosomes ________.

carry information for the same traits

In humans, blue eyes are inherited as a recessive autosomal trait and color blindness is an X-linked recessive trait. A woman with blue eyes and normal color vision whose father was color blind marries a man who also has normal color vision. He has brown eyes but his mother had blue eyes. Which of the following do you expect to be true for their daughters?

One-half of their daughters will have normal color vision and brown eyes; 1/2 of their daughters will have normal color vision and blue eyes.

In humans, blue eyes are inherited as a recessive autosomal trait and color blindness is an X-linked recessive trait. A woman with blue eyes and normal color vision whose father was color blind marries a man who also has normal color vision. He has brown eyes, but his mother had blue eyes. Which of the following do you expect to be true for their sons?

One-fourth of their sons will be color blind and have blue eyes, 1/4 of their sons will be color blind and have brown eyes, 1/4 of their sons will have normal color vision and blue eyes, 1/4 of their sons will have normal color vision and brown eyes

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