Ch 17 Protein Synthesis

Question 1

transcription

Answer 1

the synthesis of RNA from DNA (RNA then processed into mRNA)

Question 2

translation

Answer 2

the synthesis of a amino acids/polypeptide from mRNA

Question 3

ribosomes re: (protein synthesis)

Answer 3

molecular complexes that facilitate the orderly linking of amino acids into polypeptide chains

Question 4

Primary transcripts

Answer 4

initial RNA from any gene

Question 5

central dogma of biology

Answer 5

DNA -> RNA -> Protein

Question 6

genetic code

Answer 6

language of genes, codons being translated to amino acids

Question 7

codon, triplet code

Answer 7

genetic instructions for a polypeptide chain are written in the DNA as a series of nonoverlapping three nucleotide “words” (codons) in mRNA. codon codes for specific amino acid

Question 8

template strand vs coding strand

Answer 8

codons are complementary to the template strand of DNA which provides the pattern; product will match the coding (non template) strand of the DNA

Question 9

reading frame

Answer 9

nucleotides must be read in the correct groupings to code properly for amino acids

Question 10

promoter

Answer 10

DNA sequence where RNA polymerase attaches and initiates transcription

Question 11

terminator

Answer 11

DNA sequence that signals the end of transcription

Question 12

RNA polymerase

Answer 12

enzyme, pries two strands of DNA apart and elongates the RNA polynucleotide

Question 13

transcription factors

Answer 13

collection of proteins that help guide the binding of RNA polymerase

Question 14

transcription initiation complex

Answer 14

entire complex of transcription factors and RNA pol II bound to the promotor

Question 15

downstream and upstream (transcription)

Answer 15

direction of transcription is downstream, other direction is upstream

Question 16

RNA processing definition

Answer 16

enzymes in the eukaryotic nucleus modify pre-mRNA in specific ways before the genetic message is dispatched to the cytoplasm

Question 17

Poly-A tail

Answer 17

50-250 adenine nucleotides added to the 3’ end of mRNA

Question 18

RNA splicing

Answer 18

stage of RNA processing where RNA goes through a spliceosome, introns are removed and exons are reconnected

Question 19

introns, exons

Answer 19

introns are non-coding segments of nucleotides, exons will eventually be EXpressed

Question 20

spliceosome

Answer 20

large complex made of proteins and small RNAs, splices exons from introns

Question 21

alternative RNA splicing

Answer 21

a single gene can encode more than one kind of polypeptide because of the presence of introns

Question 22

domains (proteins)

Answer 22

structural and functional regions of a protein (ex: active site, binding site)

Question 23

tRNA

Answer 23

transfer RNA transfers amino acid from the cytoplasmic pool of amino acids to a growing polypeptide in a ribosome

Question 24

anticodon

Answer 24

nucleotide triplet on the tRNA that can base pair with the complementary mRNA codon

Question 25

aminoacyl-tRNA synthetases

Answer 25

a family of 20 enzymes (one for each amino acid) which ensure tRNA matches with appropriate codon

Question 26

stages of translation

Answer 26

initiation, elongation, termination

Question 27

signal peptide

Answer 27

sequence of ~20 amino acids which marks the polypeptide at the N-terminus for secretion (removed by an enzyme after ribosome lands on ER)

Question 28

signal recognition particle (SRP)

Answer 28

recognizes the signal peptide and escorts ribosome to the ER in protein synthesis

Question 29

Polyribosomes/polysomes

Answer 29

Multiple ribosomes which translate a single mRNA at the same time

Question 30

Mutations

Answer 30

changes to the genetic information of a cell, ultimate source of new genes/evolution

Question 31

Point mutations

Answer 31

small scale mutation, changes in a single nucleotide pair of a gene

Question 32

Nucleotide-pair substitution

Answer 32

the replacement of one nucleotide and its partner with another pair of nucleotides

Question 33

Silent mutation

Answer 33

substitution, no observable effect on phenotype, can occur outside genes

Question 34

Missense mutation

Answer 34

substitution, changes one amino acid to another, most common substitution

Question 35

Nonsense mutation

Answer 35

substitution, changes a codon for an amino acid into a stop codon, most lead to non functional protein

Question 36

insertion and deletion (mutation)

Answer 36

additions or losses of nucleotide pairs in a gene. can alter reading frame, more disastrous than substitutions

Question 37

Frameshift mutation

Answer 37

whenever the number of nucleotides inserted or deleted is not a multiple of three

Question 38

Mutagens

Answer 38

physical and chemical agents which interact with DNA in ways that cause mutations

Question 39

Gene editing

Answer 39

altering genes in a specific, predictable way

Question 40

CRISPER-Cas9 system

Answer 40

Gene editing technique, Cas9 is a nuclease that cuts double stranded DNA molecules, will cut any sequence for which it is directed

Question 41

transcription initiation

Answer 41

During initiation, RNA polymerase pries the two strands of DNA apart. Transcription factors attach to the DNA at the promotor region of the gene (TATA or CAAT). The RNA can then attach to the gene at the promotor region, along with the transcription factors, forming the transcription initiation complex.

Question 42

transcription elongation

Answer 42

During elongation, RNA pol adds complementary nucleotides one at a time to the 3’ end of RNA. RNA then peels away, and the double helix reforms.

Question 43

transcription termination

Answer 43

In the last stage, termination, the RNA pol II reaches the terminator (aauaaa). Polymerization stops

Question 44

translation initiation

Answer 44

requires initiation factors to bind mRNA, two subunits of the ribosome, first amino acid with its attached tRNA. Ribosome scans for “start” codon AUG which establishes reading frame.

Question 45

translation elongation

Answer 45

requires elongation factors, three steps:

a. Codon recognition – anticodon of appropriate tRNA base pairs with complementary mRNA codon in A site
b. Peptide bond formation – rRNA molecule removes polypeptide from tRNA and forms peptide bond between carboxyl end of growing polypeptide in the P site and amino of new amino acid in the A site.
c. Translocation – ribosome translocates the tRNA in the A site to the P site, and the empty tRNA in the P site is moved to the E site & released

Question 46

translation termination

Answer 46

requires release factor, ribosome reaches a stop codon (terminators are UAA, UAG, UGA), release factor promotes hydrolysis of the bond between the tRNA and the P site, frees polypeptide from the ribosome

Question 47

genetic code

Answer 47

a universal set of rules. The same codons will correlate with the same amino acid and therefore the same protein in every organism - so a gene from one organism can build the same protein in a different organism.

Question 48

ingredients & roles of translation

Answer 48

mRNA – instructions for building
tRNA – transfer an amino acid from the cytoplasmic pool of amino acids to a growing polypeptide. anticodon on one end, amino acid on other end
Ribosomes – makes polypeptides, made up of two subunits, contain ribosomal RNA (rRNA). “grooves”:
A site – arrival site
P site – placeholder site
E site – exit site

Question 49

What happens during RNA processing?

Answer 49

RNA is processed into mRNA. A 5’ cap is added to the beginning and a poly-A tail is added to the 3’ end to protect the mRNA from degradation and export it from the nucleus. Before entering the cytoplasm, the RNA goes through the spliceosome to remove the introns and join the exons together.