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BIOC4332: Biochemistry II > Exam I (Practice Exams) > Flashcards

Exam I (Practice Exams) Flashcards

1
Q

On average, exons comprise 75% of our genes. True or false?

A

True

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2
Q

Genes occupy almost a quarter of the genome. True or false?

A

True

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3
Q

Most of the human genome is highly conserved. True or false?

A

False

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4
Q

Almost half of our genome is composed of repetitive sequences. True or false?

A

True

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5
Q

Transposable elements occupy almost 10% of our genome. True or false?

A

False

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6
Q

The genomes of two individuals who are identical twins could be different by the time they reach adulthood. True or false?

A

True

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7
Q

The Alu element in our genome is an example of retroviral-like retrotransposons. True or false?

A

True

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8
Q

Tens of thousands of replication origins are used each time a cell in our body replicates its DNA. True or false?

A

True

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9
Q

Which of the following would most reliably suggest that a genomic sequence is functionally important?

A. Multispecies conservation of the sequence
B. Low copy number variation of the sequence
C. The presence of a STOP codon
D. The presence of repetitive sequences

A

A

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10
Q

The genetic information carried by a cell is passed on, generation after generation, with astonishing fidelity. However, genomes are still altered over evolutionary time scales, and even their overall size can change significantly. Which of the following genome-altering events has increased the size of the mammalian genome the most?

A. Chromosomal deletion
B. Transposition
C. Chromosomal translocation
D. Point mutation
E. Chromosomal inversion

A

B

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11
Q

If a population of cells had a mutation in which the phosphorylation of the ORC was decreased, a cell cycle analysis would most likely show (relative to cells without the mutation):

A. Cell cycle arrest in G1/G0 phase
B. No change in the relative number of cells with the respective cell cycle phase-dependent DNA content.
C. More cells with increased amounts of DNA content beyond 2N
D. Fewer cells in S phase
E. More cells with less than 1N amount of DNA content

A

C

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12
Q

The two chromosomes in each of the 22 homologous pairs in our cells…

A. have the exact same DNA sequence
B. show identical banding patterns after Giemsa staining
C. are derived from one of our parents
D. All statements are correct
E. usually bear different sets of genes

A

B

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13
Q

In human cells, the alpha satellite DNA repeats…

A. are repetitive sequences that promote transcription
B. consist in a tandem array of rDNA
C. are tandem repeats of coding DNA
D. are transposable elements
E. are tandem repeats found in the centromeres

A

E

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14
Q

Which of the following features is common between the replication origins in Escherichia coli and Saccharomyces cerevisiae?

A. Both are specified by DNA sequences of tens of thousands of nucleotide pairs
B. Both require binding of ORC
C. Both contain sequences that attract initiator proteins, as well as stretches of DNA rich in A-T base pairs
D. They both normally exist in one copy per genome
E. Both contain GATC repeats that are methylated to prevent the inappropriate “firing” of the origin

A

C

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15
Q

Gene duplication can give rise to homologous genes that are part of gene families. For example, there are six actin genes in the genome of most mammalian species. In humans, the ACTB gene, which encodes a cytoskeletal actin, is expressed ubiquitously, while ACTC1 is expressed mainly in cardiac cells. Although bacteria lack the eukaryotic cytoskeletal organization, the bacterial MreB gene bears recognizable sequence similarity to mammalian actin genes and codes for a protein that is similar to actin in structure and function. Which of the following statements is true about these genes?

A. ACTB is paralogous to ACTC1 but not to MreB
B. ACTB is paralogous to both ACTC1 and MreB
C. MreB is orthologous to ACTB but not to ACTC1
D. ACTB is orthologous to ACTC1 but not to MreB

A

A

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16
Q

Nearly half our genome is composed of:

A. Retroviruses
B. Simple repeats like those found at centromeres and telomeres
C. Retrotransposons
D. Introns
E. Exons

A

C

17
Q

Imagine a segment of DNA (within a gene) encoding a certain amount of information in its nucleotide sequence. When this segment is fully transcribed into mRNA and then translated into protein, in general…

A. the amount of information in the mRNA sequence is higher, because several mRNA molecules can be transcribed from one DNA molecule
B. the protein sequence would carry more information compared to the DNA and mRNA sequences, because its alphabet has 20 letters
C. the protein sequence would carry less information compared to the DNA and mRNA sequences, because several codons can correspond to one amino acid
D. the amount of information in the mRNA sequence is lower, because the mRNA has been transcribed using only one of the DNA strands as the template

A

C

18
Q

Which of the following accurately describes the key step that initiate(s) the transition from G1 into S phase at the start of DNA replication in eukaryotes?

A. Helicase is phosphorylated and activated
B. Helicase is released from the double stranded portion of the DNA and loaded onto single stranded DNA by the clamp loader
C. Helicase is phosphorylated and targeted for degradation by the proteasome
D. Geminin binds to Cdc6 and assists it with loading the helicase onto the origin
E. ORC is dephosphorylated and bound to Cdc6 to help load the helicase onto the origin

A

A

19
Q

The Telomerase:

A. is used for LINE transposition
B. adds polyA to the end of RNA molecules
C. adds oligo dT to the end of cDNA molecules
D. is an RNA polymerase
E. is composed of a protein and a noncoding RNA subunit

A

E

20
Q

During DNA replication in the cell, DNA primase makes short primers that are then extended by the replicative DNA polymerases. These primers…

A. are made more frequently in the leading strand than the lagging strand
B. generally have a higher number of mutations compared to their neighboring DNA
C. are made up of DNA
D. provide a 3′-phosphate group for the DNA polymerases to extend
E. are joined to the neighboring DNA by DNA ligase

A

B

21
Q

If the first three bases of a six base pair DNA palindrome are CTA, the last three bases are:

A. ATC
B. CTA
C. none
D. GAT
E. TAG

A

E

22
Q

DNA-only transposons…

A. All statements are correct
B. can be recognized by the presence of short inverted repeats at each end
C. often encode a transposase that mediates the transposition process
D. can move by a cut-and-paste mechanism
E. can leave double-strand breaks in the donor chromosome

A

A

23
Q

DNA ligases are used in both DNA replication and repair to seal breaks in the DNA. But DNA damage can result in single- or double-strand breaks that are not normal ligase substrates. These need to be processed first before a ligase can act on them. One of the enzymes that is recruited to some of such breaks is called PNK. It has two separate activities on the DNA, both of which can help provide a ligase substrate. Which of the following activities would you expect PNK to have in this context?

A. 5′ kinase (phosphorylation of a free 5′-OH group) and 3′ kinase
B. 3′ kinase and 3′ phosphatase
C. 5′ phosphatase (dephosphorylation to create a free 5′-OH group) and 3′ phosphatase
D. 5′ phosphatase and 3′ kinase
E. 5′ kinase and 3′ phosphatas

A

E

24
Q

Which enzyme does not utilize ATP hydrolysis in its mechanism?

A. Topoisomerase II
B. DnaA in E. coli
C. Topoisomerase I
D. DNA helicase
E. DNA ligase

A

C

25
Q

The nuclear DNA polymerases in human cells …

A. require ATP to unwind 3bp of double stranded DNA
B. have a single active site that is used for both polymerization and editing
C. are incapable of 3′-to-5′ exonuclease activity
D. are unable to initiate polymerization de novo (i.e. in the absence of a primer)
E. are capable of 3′-to-5′ DNA polymerase activity

A

D

26
Q

During DNA replication, the single-strand DNA-binding (SSB) proteins …

A. bind cooperatively to short hairpin helices that readily form in the single-stranded DNA
B. prevent the folding of the single-stranded DNA
C. are generally found more on the leading strand than the lagging strand
D, bind cooperatively to single-stranded DNA and cover the bases to prevent base-pairing
E. All are correct

A

B

27
Q

The sliding clamp and the DNA helicase that function at the replication fork both have three-dimensional structures resembling a ring with a central hole through which DNA is threaded. Which of these proteins, the sliding clamp or the helicase, do you think has a wider hole in its structure?

A

Sliding clamp

28
Q

Gaps in DNA are repaired by the two enzymes.

A

DNA polymerase and DNA ligase

29
Q

Recognize(s) sets of short repeats and excises the intervening DNA

A

Transposase

30
Q

Autonomously encode(s) for own reverse transcriptase

A

LINEs

31
Q

Perform(s) the unwinding of DNA in eukaryotic origin licensing

A

Helicase

32
Q

Protect(s) single stranded DNA during replication

A

RPA

33
Q

Only present on the lagging strand of replicating DNA

A

Okazaki fragments

34
Q

Proteins that recognize and cleave short (8-10 bp) sequences of DNA

A

Restriction enzymes

35
Q

Sequences missing when sequencing cDNA libraries

A

Introns

36
Q

Molecular basis of DNA hybridization

A

Hydrogen bonding

BIOC4332: Biochemistry II (7 decks)

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