d1.2 protein synthesis

Question 1

sense strand

Answer 1

actually contains the genetic material for the polypeptide

Question 2

antisense strand

Answer 2

complimentary strand
- not codable in the 5’ to 3’ direction

Question 3

mRNA vs sense strand

Answer 3

mRNA is a copy of the sense strand (T is replaced by U)

Question 4

gene

Answer 4

segment of dna that contains coded information for synthesising a polypeptide molecule

Question 5

what does ribosome convert (what to what)

Answer 5

dna to amino acid

Question 6

what is the only thing that is copied

Answer 6

gene segment

Question 7

start codon

Answer 7

AUG

Question 8

what can cells do through gene expression

Answer 8

cells can specialise into different types

Question 9

what does cell specialisation affect

Answer 9

whether or not a gene will be transcribed for ribosomes to create the necessary polypeptide

Question 10

transcription

Answer 10

first stage of gene expression, key stage at which expression of a gene can be switched on and off

Question 11

how does the dna fit in the nucleus

Answer 11

wrapped around histone to form nucleosome

Question 12

how does nucleosome affect gene expression

Answer 12

by prompting or limiting dna transcription

Question 13

what does a condensed chromatin mean

Answer 13

no genes are expressed since dna transcription is inhibited

Question 14

what does an open chromatin mean

Answer 14

genes are expressed since it promotes dna transcription

Question 15

what does the rna polymerase attach to + what does it do

Answer 15

1. unzip the double helix
2. attach onto the antisense strand (template strand)

Question 16

why does the rna polymerase attach to the antisense strand

Answer 16

as it moves, it copies and makes rna that is complementary to the antisense strand

Question 17

after transcription what do the ribosomes do (+ what do they use)

Answer 17

uses tRNA to synthesise the polypeptide using the mRNA

Question 18

what do tRNA contain

Answer 18

anticodon that is complementary to the codon in the mRNA

Question 19

what do ribosomes do after transcription at the 3’ end

Answer 19

carries the amino acid that the codon codes for

Question 20

2 types of ribosomes

Answer 20

1. free ribosomes
2. bound ribosomes

Question 21

where will all mRNA go to first

Answer 21

free ribosomes

Question 22

how to tell if a gene is expressed

Answer 22

if it is condensed, its not expressed

Question 23

how is the mRNA identical to the sense strand except T to U

Answer 23

mRNA uses RNA polymerase which attaches to the antisense strand

Question 24

what would happen is the ribosome is bound on the rough er

Answer 24

polypeptide would go outside of the cell through exocytosis

Question 25

dna structure of tRNA

Answer 25

clover leaf

Question 26

brief process of translation

Answer 26

1. initiation 2. elongation 3. termination

Question 27

detailed process of initiation

Answer 27

- mRNA enters the small unit of the ribosome - tRNA carrying Met will bind to start codon - large subunit of ribosome binds and the tRNA will fit into the p site

Question 28

detailed process of elongation

Answer 28

- another tRNA binds to the next codon at the A site - amino acid in P site will form a peptide bond with the amino acid of the A site - ribosome will move from 5' to 3' to the next codon - tRNA in the E site leaves - repeats until the stop codon hits the A site

Question 29

detailed process of termination

Answer 29

- when a stop codon enters A site, translation terminates - ribosome detaches - polypeptide detaches from the tRNA

Question 30

what does the polypeptide need to do in order for it to be functional

Answer 30

fold according to its properties

Question 31

3 types of point mutation affecting protein structure

Answer 31

1. base substitution 2. base deletion 3. base addition

Question 32

which point mutation has the least impact + why

Answer 32

base substitution doesnt change all the codons after it (reads in triples)

Question 33

how does the different amino acid in sickle cell affect the chemical properties

Answer 33

non polar - hydrophobic so it wants to be on the inside

Question 34

codon for Met (the starting codon)

Answer 34

AUG

Question 35

codons for the stop codon

Answer 35

1. UAG 2. UAA 3. UGA

Question 36

how to determine where to start reading a codon

Answer 36

- the first few codons doesnt have a stop codon

Question 37

what do non-coding sequences in dna mean

Answer 37

do not code for polypeptides

Question 38

functions of non-coding sequences in dna

Answer 38

1. telomeres 2. introns 3. base sequences

Question 39

what are telomeres

Answer 39

structures that form the end of chromosomes in eukaryotes

Question 40

what are introns

Answer 40

non coding regions within a gene that needs to be edited out

Question 41

what do only eukaryotes have

Answer 41

introns

Question 42

what are base sequences

Answer 42

- can be transcribed to produce transfer rna (tRNA), ribosomal RNA (rRNA) that makes up part of a ribosome (ribosome is made up of RNA and proteins - base sequences used to regulate gene expression (eg. promoters, enhancer and silencer) - affects gene even tho doesnt code for polypeptide itself

Question 43

what proteins affects dna transcription

Answer 43

enhancer and silencer regions

Question 44

what is the promoter proximal elements

Answer 44

proteins need to bind there to allow for transcription to start

Question 45

mechanism of silencer

Answer 45

bind and stops the promoter or rna polymerase to bind

Question 46

what does activated protein do

Answer 46

enhances transcription

Question 47

y is regulation needed

Answer 47

so not all resources are used up

Question 48

why do only eukaryotes need to do post transcription processing

Answer 48

have introns to be cut out

Question 49

process of post-transcriptional processing

Answer 49

1. splicing 2. alternative splicing 3. 5' cap 4. poly A tail

Question 50

splicing

Answer 50

removal of introns using splicesome (small nuclear ribonucleoprotein)

Question 51

why is alternative splicing needed

Answer 51

to make variations of polypeptide for different functions

Question 52

function of 5' cap

Answer 52

- prevents breakdown of the mRNA - helps regulate the export out of the nucleus - promotes translation

Question 53

function of poly A tail

Answer 53

- prevents breakdown of mRNA - keeps mRNA stable - results in mature mRNA

Question 54

conjugated proteins

Answer 54

quaternary + non polypeptide component

Question 55

name of sequence that tells ribosomes to go to rough er

Answer 55

signal sequence

Question 56

why does the protein have to go to the rough er

Answer 56

so exocytosis can occur

Question 57

what is the signal sequence not a part of

Answer 57

insulin

Question 58

prepoinsulin

Answer 58

chop off signal sequence

Question 59

3 parts of preproinsulin

Answer 59

1. b-b chain 2. a-a chain 3. connecting polypeptide

Question 60

how does the preproinsulin start folding

Answer 60

- r group - disulphide birdges between cystine

Question 61

what are used to modify the polypeptide

Answer 61

protease

Question 62

why might proteins no longer be needed

Answer 62

1. reaction ended 2. proteins changed due to denaturation/mis-folding 3. changed due to free radicals or other reactive chemicals

Question 63

name of recycling protein

Answer 63

proteaosomes

Question 64

what are proteaosomes

Answer 64

molecular machine that removes and recycles proteins into amino acids

Question 65

what tags the short protein sequences

Answer 65

ubiquitin

Question 66

what is needed to break down protein

Answer 66

atp

Question 67

role of ribosomes in translation [4]

Answer 67

translation is the production of polypeptides/proteins - mRNA binds to the ribosome - tRNA binds to the ribosome at the site where its anti-codon corresponds to the codon on the mRNA - amino acids of consecutive tRNAs bind by a peptide link in the ribosomes - the ribosome moves along the mRNA