Genetics Exam 2

Which of the following would yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)?

15 carbons with two double bonds

How many replication forks are formed when an origin of replication is opened?

2

Which of the following statements about the newly synthesized strand of a human chromosome is TRUE?

It was synthesized from multiple origins by a mixture of continuous and discontinuous DNA synthesis.

Telomeres serve as caps protecting the ends of linear chromosomes. Which of the following is FALSE regarding the replication of telomeric sequences?

The leading strand doubles back on itself to form a primer for the lagging strand.

Which of the following is most likely to occur after the lipid bilayer is pierced?

The membrane reseals.

The DNA duplex consists of two long covalent polymers wrapped around each other many times over their entire length. The separation of the DNA strands for replication causes the strands to be "overwound" in front of the replication fork. How does the cell relieve the torsional stress created along the DNA duplex during replication?

Topoisomerases break the covalent bonds of the backbone, allowing the local unwinding of DNA ahead of the replication fork.

What is one way changes in histone modifications lead to changes in chromatin structure?

They help recruit other proteins to the chromatin.

The consistent diameter of the DNA double helix arises because of which property?

base pairing of pyrimidines with purines

In the α helices of single-pass transmembrane proteins, the hydrophobic side chains face which direction?

the outside of the membrane-spanning helix

In a DNA double helix, a

the two DNA strands run antiparallel.

Although the chromatin structure of interphase and mitotic chromosomes is very compact, DNA-binding proteins and protein complexes must be able to gain access to the DNA molecule. Chromatin-remodeling complexes provide this access by

using the energy of ATP hydrolysis to move nucleosomes.

In a lipid bilayer, where do lipids rapidly diffuse?

within the plane of their own monolayer

RNA in cells differs from DNA in that

it is single-stranded and can fold up into a variety of structures.

According to current thinking, the minimum requirement for life to have originated on Earth was the formation of a

molecule that could catalyze its own replication.

Nucleotides are comprised of

nitrogenous bases + 5 carbon sugar + phosphate

Transcription is similar to DNA replication in that

nucleotide polymerization occurs only in the 5´-to-3´ direction.

The chromosomes we typically see in images are isolated from mitotic cells. These mitotic chromosomes are in the most highly condensed form. Interphase cells contain chromosomes that are less densely packed and

occupy discrete territories in the nucleus.

Proteins that are associated with the membrane by noncovalent interactions with other membrane proteins are called ___________ proteins.

peripheral membrane

The type of bond that holds together neighboring subunits in a single strand of DNA is a

phosphodiester bond.

Transporters, in contrast to channels, work by

specific recognition of transport substrates.

What type of bond connects base pairs?

Hydrogen

Genes in eukaryotic cells often have intronic sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why?

Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus.

Lipid bilayers are highly impermeable to which molecule(s)?

Na+ and Cl-

Which term correctly describes the entire phospholipid molecule?

amphipathic

Ribosomes are made up of

RNA and proteins

Sometimes, chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the adenosine in the sequence TCAT is depurinated and not repaired, which of the following is the point mutation that you would observe after this segment has undergone two rounds of DNA replication?

TCT

Which of the following occurs when a cell repairs a double-strand DNA break by the process of nonhomologous end joining (NHEJ)?

The DNA sequence at the site of repair is altered by a short deletion

Which of the following statements about the genetic code is CORRECT?

The genetic code is redundant.

Which of the following statements correctly explains what it means for DNA replication to be bidirectional?

The replication forks formed at the origin move in opposite directions.

Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?

The ribosome binds to the mRNA.

Plasma membrane proteins that move ions in and out of cells using passive transport are called

channels

The movement of an ion against its concentration gradient is called what?

active transport

Which of the following substances is most commonly used to help purify a membrane protein?

detergent

DNA replication is considered semiconservative because

each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand.

The type of chromatin that participates in the active transcription of DNA to RNA is

euchromatin

The complete set of information in an organism's DNA is called its

genome

What type of macromolecule helps package DNA in eukaryotic chromosomes?

proteins

In eukaryotes, but not in prokaryotes, ribosomes find the start site of translation by

scanning along the mRNA from the 5´ end.