ch 18: translation and mutations

Question 1

A site

Answer 1

holds an aminoacyl tRNA

Question 2

P site

Answer 2

holds the tRNA with the growing polypeptide chain attached

Question 3

E site

Answer 3

holds a tRNA that will exit

Question 4

initiation steps

Answer 4

1. first amino acid is always methionine (AUG)
2. tRNA attaches to the AUG codon
3. the large subunit of rRNA binds

Question 5

elongation steps

Answer 5

1. incoming tRNA binds to other codons and enters the A site
2. the large subunit of rRNA catalyzes peptide bonds between amino acids in P site
3. steps repeat for each codon until stop codon

Question 6

what happens after the first tRNA released its methionine?

Answer 6

it moves to the E site and dissociates from the ribosome, and tRNA can become charged again

Question 7

termination steps

Answer 7

1. translation ends when a stop codon enters the A site
2. release factor (protein) binds to stop codon and ribosome falls off mRNA transcript

Question 8

what does a stop codon not have?

Answer 8

a matching tRNA anticodon

Question 9

when does protein fold?

Answer 9

as it is being synthesized but can refold as new amino acids are added

Question 10

how is protein synthesis amplifed?

Answer 10

when many rRNAs are attached and translate an mRNA transcript

Question 11

what does the location of translation depend on?

Answer 11

the final destination of protein

Question 12

what are 3 modifications made to proteins after synthesis?

Answer 12

1. phosphorylation
2. glycosylation
3. proteolysis

Question 13

phosphorylation

Answer 13

added phosphate groups alter the shape of the protein

Question 14

glycosylation

Answer 14

adding sugars is important for targeting and recognition

Question 15

proteolysis

Answer 15

cleaving the polypeptide allows the fragments to fold in different shapes

Question 16

mutations

Answer 16

changes in the nucleotide sequence that can change protein shape and function

Question 17

causes of mutations

Answer 17

DNA replication, spontaneous chemical changes, mutagens

Question 18

somatic mutations

Answer 18

occur in body cells and have consequences for the phenotype of an individual but are not passed to offspring

Question 19

germ line mutations

Answer 19

occur in gamete cells and is passed to offsprings

Question 20

point mutations

Answer 20

changes to 1 nucleotide

Question 21

types of point mutations

Answer 21

1. silent
2. missense
3. nonsense
4. frameshift

Question 22

loss-of-function mutation

Answer 22

codes for a nonfunctional protein

Question 23

gain-of-function mutation

Answer 23

codes for a protein with a new function

Question 24

silent mutation

Answer 24

changes in the DNA bases but the amino acid stays the same due to genetic code being redundant

Question 25

do silent mutations change shape?

Answer 25

no, so they do not have a loss of function

Question 26

missense mutation

Answer 26

amino acid does change

Question 27

what are the 2 categories of missense mutations?

Answer 27

conservative and non-conservative

Question 28

conservative missence

Answer 28

chemical property of new amino acid is the same as the original - can still function

Question 29

non-conservative missense

Answer 29

chemical property of new amino acid is different from the original - creates a nonfunctional protein because it can no longer bind to the active site

Question 30

nonsense mutation

Answer 30

amino acid changes to a stop codon and the protein sentence is stopped - loss of function protein because the shape changed and cannot bind to active site

Question 31

frameshift mutations

Answer 31

addition or deletion of a DNA base, changes how the mRNA is read

Question 32

do frameshift mutations have a significant effect on final protein

Answer 32

yes, because everything after the addition or deletion is impacted

Question 33

do mutations impact alternative splicing of mRNA?

Answer 33

yes

Question 34

how do mutations impact transcription factor binding outside of protein coding region?

Answer 34

1. it can stop an activator, which stops transcription 2. it can activate a repressor, which starts transcription when it is not needed