BIOLOGY 151 EXAM 2 QUESTIONS AND
ANSWERS
X-ray crystallography - Correct Answers -Make solid DNA crystal, shine X-rays, scatter
pattern gives structural information
double helix - Correct Answers -Nucleotides covalently linked into "strand" that can
contain any sequence of nucleotides ("bases") in any order
nucleotides on double helix bonded - Correct Answers -covalently
nucleotides on one strand bond to other strand - Correct Answers -hydrogen bond
dNTPs - Correct Answers -"N"=A, C, G,T
sugar-phosphate backbone - Correct Answers -The alternating chain of sugar and
phosphate to which the DNA and RNA nitrogenous bases are attached
Phosphodiester bond - Correct Answers -the type of bond that links the nucleotides in
DNA or RNA. joins the phosphate group of one nucleotide to the hydroxyl group on the
sugar of another nucleotide
antiparallel - Correct Answers -subunits run in opposite directions
5' and 3' ends - Correct Answers -5' has phosphate group; 3' has hydroxyl group;
nucleotides added from 5 to 3
DNA REPLICATION ALWAYS OCCURS IN _____ DIRECTION - Correct Answers -5' to
3'
Complementary or matching or paired bases - Correct Answers -Base pairing: T pairs
with A; C pairs with G
Bases include thymine, adenine, cytosine, guanine
Semi-conservative - Correct Answers -build new DNA by conserving one old template
strand, building one completely new strand
,Start codon - Correct Answers -AUG!!!! Matches initiator tRNA anticodon, binds amino
acid methionine, mRNA and initator tRNA bind small ribosomal subunit, recruits large
subunit, fixing the frame of translation. Usually the most 5[' AUG
Stop codon: - Correct Answers -translation stops at one of three "nonsense" stop
codons(UAA, UAG, UGA). Binds release factor protein which releases polypeptide,
List possible causes of DNA mutations. - Correct Answers -Bad replication: some DNA
polymerases proofread by excising mismatched bases, not always successful
Chemical damage: to bases, breaks in one or both DNA strands
Selfish DNA: some virus and transposable element DNA spices in and out of DNA<
causes damage, moves surrounding genomic DNA
Predict whether a change, addition, or deletion of a DNA nucleotide leads to a specific
class of point and frameshift mutation. - Correct Answers -Deletion or insertions can
create frameshift mutations if other than 3^n nucleotides
Change in or loss of a single base results in point mutations
DNA polymerase - Correct Answers -used in DNA replicatio; matches complementary
nucleotides to template, builds new strand
Helicase - Correct Answers -An enzyme that untwists and unzips the double helix of
DNA at the replication forks.uses ATP
single strand binding proteins - Correct Answers -prevent bases from re-binding each
other
Origin of replication - Correct Answers -specific DNA sequence where helicases and
polymerases start replication
How many origins of replication do prokaryotes have - Correct Answers -one (circular)
How many origins of replication do eukaryotes have - Correct Answers -multiple (more
linear)
replication bubble - Correct Answers -helicases moving both directions with two
replication forms
replication fork - Correct Answers -A Y-shaped region on a replicating DNA molecule
where new strands are growing. made from unzipping strands and preventing bases
from re-binding to eachother
Supercoiling - Correct Answers -twisting in the opposite direction to the turns of the
double helix
, Topoisomerase - Correct Answers -cuts strands, allows them to unwind and then re-
joins them
Primase - Correct Answers -adds complementary RNA nucleotides to DNA template,
builds short RNA primer
RNA primer - Correct Answers -short segment of RNA used to initiate synthesis of a
new strand of DNA during replication.
Bonding site for DNA polymerse - Correct Answers -RNA primer
DNA ligase - Correct Answers -enzyme that chemically links DNA fragments together
Leading strand - Correct Answers -The new continuous complementary DNA strand
synthesized along the template strand in the mandatory 5' to 3' direction. follows
helicase
lagging strand - Correct Answers -The strand that is synthesized in fragments using
individual sections; keeps restarting
Okazaki fragments - Correct Answers -Small fragments of DNA produced on the lagging
strand during DNA replication
Telomere - Correct Answers -repeating nucleotide at the ends of DNA molecules that do
not form genes and help prevent the loss of genes
Telomerase - Correct Answers -An enzyme that catalyzes the lengthening of telomeres
Transcription - Correct Answers -synthesis of an RNA molecule from a DNA template
mRNA - Correct Answers -messenger RNA; type of RNA that carries instructions from
DNA in the nucleus to the ribosome
RNA polymerase - Correct Answers -enzyme that links together the growing chain of
RNA nucleotides during transcription using a DNA strand as a template
Promoter - Correct Answers -nucleotides bound by RNA polymerase and cofactors,
where transcription begins
Terminator - Correct Answers -In prokaryotes, a special sequence of nucleotides in
DNA that marks the end of a gene.
Transcription unit - Correct Answers -A region of DNA that is transcribed into an RNA
molecule by mRNA
ANSWERS
X-ray crystallography - Correct Answers -Make solid DNA crystal, shine X-rays, scatter
pattern gives structural information
double helix - Correct Answers -Nucleotides covalently linked into "strand" that can
contain any sequence of nucleotides ("bases") in any order
nucleotides on double helix bonded - Correct Answers -covalently
nucleotides on one strand bond to other strand - Correct Answers -hydrogen bond
dNTPs - Correct Answers -"N"=A, C, G,T
sugar-phosphate backbone - Correct Answers -The alternating chain of sugar and
phosphate to which the DNA and RNA nitrogenous bases are attached
Phosphodiester bond - Correct Answers -the type of bond that links the nucleotides in
DNA or RNA. joins the phosphate group of one nucleotide to the hydroxyl group on the
sugar of another nucleotide
antiparallel - Correct Answers -subunits run in opposite directions
5' and 3' ends - Correct Answers -5' has phosphate group; 3' has hydroxyl group;
nucleotides added from 5 to 3
DNA REPLICATION ALWAYS OCCURS IN _____ DIRECTION - Correct Answers -5' to
3'
Complementary or matching or paired bases - Correct Answers -Base pairing: T pairs
with A; C pairs with G
Bases include thymine, adenine, cytosine, guanine
Semi-conservative - Correct Answers -build new DNA by conserving one old template
strand, building one completely new strand
,Start codon - Correct Answers -AUG!!!! Matches initiator tRNA anticodon, binds amino
acid methionine, mRNA and initator tRNA bind small ribosomal subunit, recruits large
subunit, fixing the frame of translation. Usually the most 5[' AUG
Stop codon: - Correct Answers -translation stops at one of three "nonsense" stop
codons(UAA, UAG, UGA). Binds release factor protein which releases polypeptide,
List possible causes of DNA mutations. - Correct Answers -Bad replication: some DNA
polymerases proofread by excising mismatched bases, not always successful
Chemical damage: to bases, breaks in one or both DNA strands
Selfish DNA: some virus and transposable element DNA spices in and out of DNA<
causes damage, moves surrounding genomic DNA
Predict whether a change, addition, or deletion of a DNA nucleotide leads to a specific
class of point and frameshift mutation. - Correct Answers -Deletion or insertions can
create frameshift mutations if other than 3^n nucleotides
Change in or loss of a single base results in point mutations
DNA polymerase - Correct Answers -used in DNA replicatio; matches complementary
nucleotides to template, builds new strand
Helicase - Correct Answers -An enzyme that untwists and unzips the double helix of
DNA at the replication forks.uses ATP
single strand binding proteins - Correct Answers -prevent bases from re-binding each
other
Origin of replication - Correct Answers -specific DNA sequence where helicases and
polymerases start replication
How many origins of replication do prokaryotes have - Correct Answers -one (circular)
How many origins of replication do eukaryotes have - Correct Answers -multiple (more
linear)
replication bubble - Correct Answers -helicases moving both directions with two
replication forms
replication fork - Correct Answers -A Y-shaped region on a replicating DNA molecule
where new strands are growing. made from unzipping strands and preventing bases
from re-binding to eachother
Supercoiling - Correct Answers -twisting in the opposite direction to the turns of the
double helix
, Topoisomerase - Correct Answers -cuts strands, allows them to unwind and then re-
joins them
Primase - Correct Answers -adds complementary RNA nucleotides to DNA template,
builds short RNA primer
RNA primer - Correct Answers -short segment of RNA used to initiate synthesis of a
new strand of DNA during replication.
Bonding site for DNA polymerse - Correct Answers -RNA primer
DNA ligase - Correct Answers -enzyme that chemically links DNA fragments together
Leading strand - Correct Answers -The new continuous complementary DNA strand
synthesized along the template strand in the mandatory 5' to 3' direction. follows
helicase
lagging strand - Correct Answers -The strand that is synthesized in fragments using
individual sections; keeps restarting
Okazaki fragments - Correct Answers -Small fragments of DNA produced on the lagging
strand during DNA replication
Telomere - Correct Answers -repeating nucleotide at the ends of DNA molecules that do
not form genes and help prevent the loss of genes
Telomerase - Correct Answers -An enzyme that catalyzes the lengthening of telomeres
Transcription - Correct Answers -synthesis of an RNA molecule from a DNA template
mRNA - Correct Answers -messenger RNA; type of RNA that carries instructions from
DNA in the nucleus to the ribosome
RNA polymerase - Correct Answers -enzyme that links together the growing chain of
RNA nucleotides during transcription using a DNA strand as a template
Promoter - Correct Answers -nucleotides bound by RNA polymerase and cofactors,
where transcription begins
Terminator - Correct Answers -In prokaryotes, a special sequence of nucleotides in
DNA that marks the end of a gene.
Transcription unit - Correct Answers -A region of DNA that is transcribed into an RNA
molecule by mRNA
