Chapter 13: Gene Structure and Expression

Question 1

Transcription of a gene occurs in what three steps?

Answer 1

• initiation
• elongation
• termination

Question 2

guanine cap

Answer 2

added to 5` end of the pre-mRNA by a capping enzyme during transcription
-protects mRNA from degradation and where the ribosomes attach during translation

Question 3

direction of transcription

Answer 3

downstream

Question 4

transcription initiation complex

Answer 4

transcription factors and RNA polymerase

Question 5

In eukaryotes, added to the 3` end during replication is….

Answer 5

polyadenylation signal (poly A polymerase adds a chain of 50 to 250 adenine nucleotides)

Question 6

mRNA

Answer 6

messenger RNA; possesses the code for a particular polypeptide chain on it

Question 7

codon

Answer 7

3 nucleotide bases that code for a particular amino acid

Question 8

How many codons are there?

Answer 8

64 (60 without the start codon and stop codons)

Question 9

AUG

Answer 9

start codon (starts translation)

Question 10

Bacterial mRNAs can usually be __________.

Answer 10

immediately translated

Question 11

Prokaryotic mRNAs are translated by ribosomes ______________.

Answer 11

while they are still being transcribed by RNA polymerases

Question 12

pre-mRNA

Answer 12

precursor mRNA (initial mRNA transcribed)

Question 13

After processing the RNAs are called….

Answer 13

mature mRNAs

Question 14

Eukaryote mRNAs must undergo ___________ before they are ready to leave the nucleus.

Answer 14

processing in the nucleus

Question 15

poly (A) tail

Answer 15

protects the RNA from attack by RNA digesting enzymes in the cytosol

Question 16

introns

Answer 16

sections not included in the mature mRNAs

Question 17

exons

Answer 17

sections that are included in the mature mRNA and translated

Question 18

RNA splicing

Answer 18

removes introns

Question 19

ribosomes are….

Answer 19

ribonucleoprotein particles (ribosomal RNA and proteins)

Question 20

initiator tRNA

Answer 20

anticodon UAC

Question 21

stop codons

Answer 21

UAG, UAA, UGA (they have no complementary anticodon)

Question 22

release factor protein

Answer 22

binds to stop codons

Question 23

polysome/polyribosome

Answer 23

an mRNA and associated ribosomes (speeds up the synthesis of the required polypeptide)

Question 24

after proteins leave the ribosome, most are folded or modified in what is called….

Answer 24

post translational modification

Question 25

In many animals mutations have to affect cells in the _____________ in order to be passed on to subsequent generations.

Answer 25

germ line

Question 26

somatic mutations do not have evolutionary significance in animals unless it’s an animal capable of reproducing by…

Answer 26

cloning

Question 27

base substitution mutations

Answer 27

-incorrect base is substituted, resulting in a change in base sequence on both strands (change in a codon)

Question 28

silent mutation

Answer 28

if the amino acid coded for is exactly the same the one one coded for by the original codon

Question 29

missense mutation

Answer 29

cause a change in a single amino acid in the encoded polypeptide

Question 30

nonsense mutations

Answer 30

converts a normal codon to a stop codon causing the translation to stop

Question 31

frameshift mutation

Answer 31

addition or deletion of a nucleotide