Chapter 17 - Gene Expression: From Gene to Protein

Question 1

pre-mRNA processing

Answer 1

5’ cap
splicing
poly-A-tail
-several mRNAs can be generated from a single pre-mRNA

Question 2

transcription

Answer 2

synthesis of RNA using information in the DNA

1. initiation
2. elongation
3. termination

Question 3

initiation

Answer 3

promotes signal start point, extend many nucleotide pairs upstream of point
-transcription factors mediate RNA polymerase binding/initiation (transcription initiation complex and TATA box)

Question 4

transcription initiation complex

Answer 4

assembly of factors/RNA polymerase II bound to a promoter

Question 5

TATA box

Answer 5

promoter element used for initiation complex in eukaryotes

Question 6

elongation

Answer 6

RNA polymerase moves along DNA, untwisting 10-20 base pairs at a time
-nucleotides added to 3’ end of RNA molecule

Question 7

termination

Answer 7

RNA polymerase II transcribes polyadenylation signal sequence (AAUAAA)
-transcript is released 10-35 nucleotides past poly-A sequence

Question 8

function of 5’ and poly-A-tail

Answer 8

• facilitate export of mRNA to cytoplasm
• protect mRNA from hydrolytic enzymes
• help ribosome attach to 5’ end

Question 9

non-coding regions

Answer 9

intervening sequences, introns lie between coding regions

-promoter elements can be inside an intron

Question 10

exons

Answer 10

expressed part of gene, translated into amino acid sequences

Question 11

RNA splicing

Answer 11

removes introns and joins exons

Question 12

spliceosomes

Answer 12

variety of protein and snRNPs (small nuclear ribonucleoproteins) that recognize splice sites RNAs catalyze splicing reaction

Question 13

ribozymes

Answer 13

catalytic RNA molecules (enzymes)

Question 14

alternative RNA splicing

Answer 14

genes encode for more than one polypeptide (depends on exon splicing)

Question 15

exon shuffling

Answer 15

evolution of new proteins

Question 16

translation (3 steps)

Answer 16

1. codon recognition: tRNA anticodon pairs with complementary mRNA codon in A-site
2. peptide bond formation: rRNA catalyzes formation, removes polypeptide from P-site tRNA and attaches it to amino acid of tRNA in A-site
3. translocation: tRNA from A-site to P-site to E-site and released, process repeated

Question 17

co-translational import

Answer 17

1. polypeptide synthesis begins, SRP binds to signal peptide and receptor protein in ER membrane
2. STP leaves and polypeptide synthesis resumes
3. signal-cleaving enzyme cuts of signal peptide
4. polypeptide leaves the ribosome and folds into final conformation

Question 18

silent mutation

Answer 18

no effect on amino acid sequence

TTT > AAA > Lys

Question 19

missense mutation

Answer 19

single nucleotide change causes codon coding to become a different amino acid (Gly becomes Ser)

Question 20

nonsense mutation

Answer 20

single nucleotide change causes codon coding to become a stop codon (Lys to STOP)

Question 21

frameshift insertion

Answer 21

causes immediate nonsense; nucleotide insertion (AUGUAA)

Question 22

frameshift deletion

Answer 22

causing extensive nonsense; nucleotide deletion

Question 23

central dogma

Answer 23

cells are governed by cellular chain of command

DNA>RNA>protein