Chapter 9: Molecular Biology

Question 1

alternative RNA splicing

Answer 1

a post-transcriptional gene regulation mechanism in eukaryotes in which multiple protein products are produced by a single gene through alternative splicing combinations of the RNA transcript

Question 2

codon

Answer 2

three consecutive nucleotides in mRNA that specify the addition of a specific amino acid or the release of a polypeptide chain during translation

Question 3

deoxyribose

Answer 3

a five-carbon sugar molecule with a hydrogen atom rather than a hydroxyl group in the 2’ position; the sugar component of DNA nucleotides

Question 4

DNA ligase

Answer 4

the enzyme that catalyzes the joining of DNA fragments together

Question 5

DNA polymerase

Answer 5

an enzyme that synthesizes a new strand of DNA complementary to a template strand

Question 6

double helix

Answer 6

the molecular shape of DNA in which two strands of nucleotides wind around each other in a spiral shape

Question 7

epigenetic

Answer 7

describing non-genetic regulatory factors, such as changes in modifications to histone proteins and DNA that control accessibility to genes in chromosomes

Question 8

exon

Answer 8

a sequence present in protein-coding mRNA after completion of pre-mRNA splicing

Question 9

gene expression

Answer 9

processes that control whether a gene is expressed

Question 10

genetic code

Answer 10

the amino acids that correspond to three-nucleotide codons of mRNA

Question 11

helicase

Answer 11

an enzyme that helps to open up the DNA helix during DNA replication by breaking the hydrogen bonds

Question 12

intron

Answer 12

non–protein-coding intervening sequences that are spliced from mRNA during processing

Question 13

lagging strand

Answer 13

during replication of the 3’ to 5’ strand, the strand that is replicated in short fragments and away from the replication fork

Question 14

leading strand

Answer 14

the strand that is synthesized continuously in the 5’ to 3’ direction that is synthesized in the direction of the replication fork

Question 15

mismatch repair

Answer 15

a form of DNA repair in which non-complementary nucleotides are recognized, excised, and replaced with correct nucleotides

Question 16

mRNA

Answer 16

messenger RNA; a form of RNA that carries the nucleotide sequence code for a protein sequence that is translated into a polypeptide sequence

Question 17

mutation

Answer 17

a permanent variation in the nucleotide sequence of a genome

Question 18

nitrogenous base

Answer 18

a nitrogen-containing molecule that acts as a base; often referring to one of the purine or pyrimidine components of nucleic acids

Question 19

nontemplate strand

Answer 19

the strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA

Question 20

nucleotide excision repair

Answer 20

a form of DNA repair in which the DNA molecule is unwound and separated in the region of the nucleotide damage, the damaged nucleotides are removed and replaced with new nucleotides using the complementary strand, and the DNA strand is resealed and allowed to rejoin its complement

Question 21

Okazaki fragments

Answer 21

the DNA fragments that are synthesized in short stretches on the lagging strand

Question 22

phosphate group

Answer 22

a molecular group consisting of a central phosphorus atom bound to four oxygen atoms

Question 23

post-transcriptional

Answer 23

control of gene expression after the RNA molecule has been created but before it is translated into protein

Question 24

primer

Answer 24

a short stretch of RNA nucleotides that is required to initiate replication and allow DNA polymerase to bind and begin replication

Question 25

promoter

Answer 25

a sequence on DNA to which RNA polymerase and associated factors bind and initiate transcription

Question 26

replication fork

Answer 26

the Y-shaped structure formed during the initiation of replication

Question 27

RNA polymerase

Answer 27

an enzyme that synthesizes an RNA strand from a DNA template strand

Question 28

rRNA

Answer 28

ribosomal RNA; molecules of RNA that combine to form part of the ribosome

Question 29

semiconservative replication

Answer 29

the method used to replicate DNA in which the double-stranded molecule is separated and each strand acts as a template for a new strand to be synthesized, so the resulting DNA molecules are composed of one new strand of nucleotides and one old strand of nucleotides

Question 30

splicing

Answer 30

the process of removing introns and reconnecting exons in a pre-mRNA

Question 31

start codon

Answer 31

the AUG (or, rarely GUG) on an mRNA from which translation begins; always specifies methionine

Question 32

stop codon

Answer 32

one of the three mRNA codons that specifies termination of translation

Question 33

telomerase

Answer 33

an enzyme that contains a catalytic part and an inbuilt RNA template; it functions to maintain telomeres at chromosome ends

Question 34

telomere

Answer 34

the DNA at the end of linear chromosomes

Question 35

template strand

Answer 35

the strand of DNA that specifies the complementary mRNA molecule

Question 36

transcription bubble

Answer 36

the region of locally unwound DNA that allows for transcription of mRNA

Question 37

tRNA

Answer 37

transfer RNA; an RNA molecule that contains a specific three-nucleotide anticodon sequence to pair with the mRNA codon and also binds to a specific amino acid