1. In a DNA double helix, _____________________. (a) the two DNA strands are ide
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Question
1. In a DNA double helix, _____________________.
(a) the two DNA strands are identical.
(b) purines pair with purines.
(c) thymine pairs with cytosine.
(d) the two DNA strands run antiparallel to one another.
(e) adenine pairs with uracil.
2. Fred Griffith studied two strains of Streptococcus pneumonia, one that causes a lethal infection when injected into mice, and a second that is harmless. He observed that pathogenic bacteria that have been killed by heating can no longer cause an infection. But when these heat-killed bacteria are mixed with live, harmless bacteria, this mixture is capable of infecting and killing a mouse. What did Griffith conclude from this experiment?
(a) The infectious strain cannot be killed by heating.
(b) The heat-killed pathogenic bacteria “transformed” the harmless strain into a lethal one.
(c) The harmless strain somehow revived the heat-killed pathogenic bacteria.
(d) The mice had lost their immunity to infection with S. pneumoniae.
(e) The result obtained is cannot be scientifically explained.
3. Because hydrogen bonds hold the two strands of a DNA molecule together, the strands can be separated without breaking any covalent bonds. Every unique DNA molecule “melts” at a different temperature. In this context, Tm (melting temperature) is the point at which two strands separate, or become denatured. Which of the following sequences has the lowest melting temperature?
(a) 5’GGCGCACC-3’ 3’-----------------5’
(b) 5’-TATTGTCT-3’ 3’-----------------5’
(c) 5’-GACTCCTG-3’ 3’-----------------5’
(d) 5’-CTAACTGG-3’ 3’-----------------5’
(e) 5’-TATATGGC-3’ 3’-----------------5’
4. DNA replication is considered semiconservative because ___________________________.
(a) after many rounds of DNA replication, the original DNA double helix is still intact.
(b) each daughter DNA molecule consists of two new strands copied from the parent DNA
molecule.
(c) each daughter DNA molecule consists of one strand from the parent DNA molecule and
one new strand.
(d) new DNA strands must be copied from a DNA template.
(e) only half each strand is conserved, and the other half is variable
5. Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because________________.
(a) RNA contains uracil and uses ribose as the sugar.
(b) RNA bases cannot form hydrogen bonds with each other.
(c) RNA nucleotides use a different chemical linkage between nucleotides compared to DNA.
(d) RNA is single-stranded.
(e) RNA contains stretch of nucleotides that can base-pair with complementary sequence
within the single stranded RNA
6. Which of the following statements correctly explains what it means for DNA replication to be bidirectional?
(a) The replication fork can open or close, depending on the conditions.
(b) The DNA replication machinery can move in either direction on the template strand.
(c) Replication-fork movement can switch directions when the fork converges on another
replication fork.
(d) The replication forks formed at the origin move in opposite directions.
7. Which of the following statements about the proteasome is false?
(a) Ubiquitin is a small protein that is covalently attached to proteins to mark them for
delivery to the proteasome.
(b) Proteases reside in the central cylinder of a proteasome.
(c) Misfolded proteins are delivered to the proteasome, where they are sequestered from the
cytoplasm and can attempt to refold.
(d) The protein stoppers that surround the central cylinder of the proteasome use the energy
from ATP hydrolysis to move proteins into the proteasome inner chamber
8. RNA in cells differs from DNA in that ___________________.
(a) it contains the base uracil, which pairs with cytosine.
(b) it is single-stranded and cannot form base pairs.
(c) it is single-stranded and can fold up into a variety of structures.
(d) the sugar ribose contains fewer oxygen atoms than does deoxyribose.
9. Translation in prokaryotes is initiated by ____ , ____, ____, and ____, whereas translation is eukaryotes is initiated by ____, and proteins that are bound at the 5’ ____ and
_____ at the 3’end
(a) IF1; IF2; IF3; translation initiation factors; cap; tRNA
(b) IF1-GTP; IF2; IF3; translational initiation factors; cap; polyA tail
(c) IF1; IF2; IF3-GTP; translation initiation factors; codon; polyA tail
(d) IF1; IF2-GTP; IF3; translation initiation factors; cap; polyA tail
(e) IF1, EF-Tu-GTP; IF-G-GTP; translation initiation factors; cap; polyA tail
10. For a cell’s genetic material to be used, the information is first copied from the DNA into the nucleotide sequence of RNA in a process called ____________. Various kinds of RNA are produced, each with different functions: ________ molecules code for proteins, __________ molecules act as adaptors for protein synthesis, ___________ molecules are integral components of the ribosome, and __________ molecules are important in the splicing of RNA transcripts.
(a) translation; mRNA; tRNA; rRNA; SnRNP
(b) transcription; mRNA; tRNA, rRNA; SnRNP
(c) replication; DNA; tRNA, rRNA; SnRNA
(d) transcription; tRNA; mRNA; rRNA; SnRNA
(e) translation; mRNA; rRNA; SnRNA; tRNA
Explanation / Answer
1.d) the two DNA strands run antiparallel to one another.
2.(b) The heat-killed pathogenic bacteria “transformed” the harmless strain into a lethal one.
3. a) 5’GGCGCACC-3’ 3’-----------------5’
Because there are present 3 hydrogen bonds between G and C, it will require more energy to melt the strand.
4. (c) each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand.
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