DNA and RNA Structure and Function Quiz Answers

Base pairs in DNA

A-T and C-G

Bond that hybridizes base pairs

Hydrogen bond

Chemical feature determining the 3'-end of DNA

a hydroxyl group

Chemical feature determining the 5'-end of DNA

a phosphate group

True statement for most genes

All statements are true

Eukaryotic chromosomes and origin of replication

False

Structure at the end of a linear eukaryotic chromosome

telomere

Genomic DNA associated with nuclear packing proteins

chromatin

Determination of origin of replication (ORI)

a specific DNA sequence MOTIF that delimits a DNA region as an ORI and a set of ORI specific proteins

microRNAs and their function

interfering with translation of proteins

Direction of replication forks at an origin of replication

in opposite directions

Direction of DNA synthesis

from 5' to the 3' direction

Synthesis of leading and lagging strands at a replication fork

continuously and discontinuously, respectively

Proofreading function of DNA polymerase

before adding the next nucleotide in the chain

Function of single-stranded binding proteins (SSP) in DNA replication

SSP bind to single-stranded DNA and prevent re-hybridization and formation of double stranded DNA

Function of the sliding clamp in DNA replication

it keeps DNA polymerase firmly attached to the template while it synthesizes a new strand of DNA

Enzyme that replicates the ends of chromosomes

telomerase

Depurination

the loss of a A or a G from DNA

Ultraviolet radiation damage to DNA

it promotes covalent linkage between two adjacent pyrimidine bases

Enzyme that seals a repaired DNA strand

DNA ligase

ligase

An enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.

DNA mismatch repair system

A system that corrects copying errors not flagged by the replication machinery.

double stranded break repair end-joining

A process that repairs double-stranded DNA breaks, altering the original DNA sequence at the repair site by a short deletion.

thymine

A nitrogenous base that is not present in RNA.

U

The base that pairs with base A in RNA.

transcription

The process by which all types of RNAs are synthesized in cells.

phosphodiester bond

The type of covalent bond that RNA polymerase uses to link nucleotides together.

5' to 3'

The direction in which RNA molecules elongate (synthesize).

RNA polymerase

An enzyme that begins the synthesis of an RNA molecule without a primer.

error rate of RNA polymerase

Higher than DNA polymerase's rate (1 error in 10 million nucleotides) because RNA polymerase is unable to proofread its own synthesis activity.

sigma factor

A protein that recruits RNA polymerase to the promoter site located upstream of a gene soon to be transcribed in prokaryotes.

Eukaryotic RNA polymerase

An enzyme that needs to be phosphorylated to begin transcription.

lariat

The RNA intron sequence that is spliced out by snRNPs during RNA splicing.

capped and polyadenylated

The process by which eukaryotic mRNAs are modified at the 5'-end and 3'-end, respectively.

reading frames in RNA

In principle, there are 3 potential reading frames that can be translated into proteins.

codons in mRNA (more than one)

Some codons do not code for more than one amino acid.

wobble effect

The third position in codon assignments is not always constant.

reading frame +1

The coding frame for the RNA segment AGUCUAGGCCACUGA that is in the middle of a coding region.

aminoacyl-tRNA synthase

The enzyme that couples the tRNA to the correct amino acid.

functions of rRNAs in ribosomal structure

rRNAs do more than just provide structural support to large protein aggregates like ribosomes.

AUG

The codon at which translation of a mRNA begins.

methionine

The first amino acid carried by the first tRNA when translation begins.

stop codons

Codons like UAG, UAA, and UGA that recognize special termination factor proteins.