Practice Exam

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Updated March 2011

DNA, RNA structure and function

Why are multiple copies of tRNA and rRNA genes needed?
a. These RNAs are destroyed very rapidly.
b. These RNAs are very stable.
c. These RNAs are needed in large amounts.
d. These RNAs do not benefit from the extra amplification step that occurs for protein-encoding genes. e. c and d

If you treat mitotic chromosomes with solutions that extract histones, what happens? a. The chromosomes become more condensed.
b. The DNA separates into two single strands instead of remaining as a double helix. c. Histone-free DNA can be seen to extend outward as loops from a protein scaffold. d. The chromosomes precipitate.

e. The chromosomes become branched

What postulates that the state and activity of a particular region of chromatin depends upon the specific modifications, or combination of modifications, to the histone tails in that region? It suggests that the pattern of modifications adorning the tails of the core histones contains encoded information governing the properties of the nucleosomes containing them. a. the DaVinci code

b. the chemiosmotic hypothesis
c. the histone code
d. the genetic code
e. the endosymbiotic hypothesis

For DNA structure, more compact structures are based upon simpler structures. Explain what this means.

Replication

Which type of replication results in 2 duplexes made of one parental strand and one newly synthesized strand? a. semiconservative replication
b. conservative replication
c. dispersive replication
d. incisive replication
e. reservative replication

In eucaryotes replication moves out from the origin in ________ directions and is said to be ________. a. opposite, unidirectional
b. opposite, bidirectional
c. three, bidirectional
d. unique, unidirectional
e. common, bidirectional

Some DNAs are circular and some are linear. How does this fact affect DNA synthesis?

Transcription

Which eukaryotic RNA polymerase synthesizes mRNAs and most small nuclear RNAs? a. RNA polymerase I
b. RNA polymerase II
c. RNA polymerase III
d. RNA polymerase IV
e. RNA polymerase V

What suggests the high rRNA synthesis rate in the nucleolus? a. the length of the transcripts
b. the width of the transcripts
c. the low density of RNA polymerase molecules along the transcriptional unit d. the high density of RNA polymerase molecules along the transcriptional unit e. a and d

RNA is transcribed and then modified. What modifications affect non protein-coding genes and how do they do it (2 examples)

Translation

You travel to another planet and discover that its genetic system is based on DNA, but it has 6 bases instead of 4 as happens on Earth. The proteins on the planet have 30 amino acids. What would be the likely number of letters in each codon on this planet? a. 1

b. 2
c. 3
d. 4
e. 6

What are the three distinct activities of protein synthesis in the correct order? a. initiation, elongation, termination
b. termination, initiation, elongation
c. initiation, termination, elongation
d. elongation, initiation, termination
e. elongation, termination, initiation

If AUG is not the start codon in every organism, then what is?

Regulation

If lactose is present in the medium in which bacteria are being cultured, which of the following statements is true? a. β-galactosidase is not needed.
b. β-galactosidase is present at less than 5 copies per cell. c. β-galactosidase is present at about 5000 molecules per cell d. β-galactosidase mRNA is transcribed.
e. c and d

What happens if cAMP is added to the bacterial culture medium along with glucose? a. The lac operon remains inactive.
b. The lac operon is turned on.
c. The enzymes of the lac operon are suddenly synthesized by the bacterial...
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