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Flashcards in Translation_Molecules Deck (61):
1

What carries out translation?

Ribosomes

2

What is translation?

Protein synthesis when there is a conversion of RNA code to AA code

3

What does mRNA get translated by?

1) Ribosome
2) rRNA and proteins
3) peptide bond formation catalysed by rRNA (not protein enzyme)

4

What is translation regulated by?

microRNA (miRNA)

5

How does miRNA regulate translation?

suppress growth inhibitor -> too much miRNA

6

Can you go directly from protein to RNA?

No can't use it to transfer information to RNA directly

7

What structures are visible under a microscope?

Ribosome
mRNA (gets stained)

8

A sequence of 2 bases can specify what?

4^2 (16) AA
and
4^3 (64) AA

9

Why can a single base in the mRNA not specific an AA in a polypeptide?

mRNA has only four bases but polypeptides contain 20 AA

10

What are codons?

a sequence of three bases on the mRNA codes for an AA

11

What direction does the ribosome read the codon?

5' -> 3' direction

12

What happens when the ribosome moves along the mRNA in the 5' -> 3' direction?

It synthesises the polypeptide in the amino -> carboxyl terminal direction

13

What are the properties of genetic code?

1) Colinear
2) nonoverlapping and "commaless"
3) Degenerate
4) Contains 61 AA coding codons and the three stop codons UAA, UAG, UGA
5) unambigious
6) Universal

14

What does it mean that the genetic code is colinear

sequence of AA in the polypeptide from amino end to carboxyl end, corresponds exactly to the sequence of their codons in the mRNA, read form 5' -> 3'

15

What does it mean the genetic code is non overlapping and "commaless"

Codons are aligned without overlapping and without empty spaces in between. Each base belongs to only one codon.

16

What does it mean the genetic code is degenerate

More than one codon can code for an AA

17

What does it mean that the genetic code is unambiguous?

Each codon specifies one and only one AA

18

What does it mean that the genetic code is universal?

With the minor exception of the start codon AUG, the code is identical in prokaryotes and eukaryotes

19

What breaks the properties of genetic code?

Synthesising mRNA could make a new protein.
e.g.
1) poly U -> poly Phe
2) poly C -> poly Pro
3) poly random (U,small amount of C) -> Phe, Pro, Ser and Lys
4) poly (AU) -> Ile-Tyr-Ile-Tyr-...

20

What is the start codon?

AUG

21

What is the stop/termination/nonsense codon?

UAA
UAG
UGA

22

What is the exception that slightly doesn't follow the genetic code in the human body?

Mitochondria

23

When you silent a codon, which position is normally silenced

the third position

24

What does AUG also code for?

Methionine

25

What are the two types of mutations?

1) Point mutation
2) Frameshift mutation

26

What are examples of point mutations and what are they?

Silent mutations - degenerate positions
Missense mutations - change AA
Nonsense mutations - create stop codon
Change stop codon tonne stop - "read through mutations - get a longer protein

27

What does point mutations do?

Change one base

28

What is frame shift mutation?

insert or delete 1,2,4,5,7 etc bases -> random with respect to protein

29

What happens during silent mutation?

Normally no phenotypic change
Can alter splicing causing disease and cancer

30

How is silent mutations detected by?

DNA sequencing or mRNA sequencing (can't see by sequencing protein or AA)

31

What are examples of silent mutations?

SNP (single nucleotide polymorphism)
Codon usage in bacterial and virus genomes not random

32

What is an example of missense mutation

Haemoglobinpathies
- Sickle cell anaemia
- GAA -> GUA OR
- GAG -> GUG at codon 6
- hundred other globin mutations known

33

What is an example of nonsense mutation?

Thalassaemias
- imbalance in globin production or absence of one globin
- e.g. AAG -> UAG at codon 17 of beta globin (beta thalassemia)
- entire globin gene missing

34

What happens in alpha thalassaemia?

4 copies of alpha globin gene
- 2 on each chromosome 16
- deletion of 1 - 4 copies causes disease
- also "read through" mutation of stop codon -> abnormally long alpha globin chains

35

How many transfer RNA are there?

Approx 50 per organism, one or more for each AAA

36

How many tRNA syntheses are there?

20
- attach 1 AA to one tRNA

37

Each tRNA recognises how many codons?

1 or 2 codons
- modified nucleotide at the 3rd position and can recognise at the silent position

38

What do ribosome need to do?

1) Bind to mRNA
2) Recognise start of coding sequence
3) Move along coding sequence
-> read RNA, codon by codon from 5' -> 3'
-> Add amino acids to protein chain from N terminus to C terminus
-> need an "adaptor" molecule which is tRNA

39

When reading nucleotype what happens?

need to use another nucleic acid/nucleotype because H bonding is completely specific

40

What are the features of tRNA?

1) Approximately 70 nucleotide long
2) AA attached at 3' end
3) All end in CCA

41

What type of structure does the tRNA have?

Clover leaf structure

42

What is Gm and what does the Gm AA read in tRNA

Methylated G
UUC

43

What is the codon recognised by?

Anticodon

44

What are the prominent features of tRNA?

1) Modified nucleotides
2) Methylated bases
3) Thymine
4) Pseudouridine

45

What are the two subunits of ribosome?

Large
Small

46

What does S stand for?

Svedberg unit: centrifugation size

47

What does the small subunit contain (in humans)?

1) 34 proteins
2) one RNA -> SSU or 18S rRNA

48

What does the large subunit contain (in humans)?

1) 50 proteins
2) 3 RNA
- LSU or 28S rRNA
- 5.8 S and 5S

49

Looking in atomic detail, when does the 2 subunits attach?

Attach to each other on a mRNA to carry out translation other than that they don't attach

50

Prokaryotes have what type of ribosome?

70S ribosome
- small (30S) and large (50S)

51

What does the small subunit bind to?

Larger subunit
mRNA pattern

52

What does the large subunit bind to?

Smaller subunit
tRNA
AA

53

Eukaryotes have what type of ribosome?

80S ribosome
- small (40S) and large (60S) subunit

54

What happens during translation?

1) Start with Met at first AA
2) Add AAs in order specified by codons (in frame)
3) Stop at stop codon
4) Post translational modification

55

What happens during translation?

Ribosomes need to be positioned correctly

56

What is Shine-Dalgarno sequence?

Ribosomal binding site in bacteria, generally located around 9 - 10 nucleotide away from the AUG codon

57

In humans, where is first AUG sometimes?

in MRNA

58

What does the Shine-Dalgarno sequence do?

RNA sequence helps recruit the ribosome to the messenger RNA (mRNA) to initiate protein synthesis by aligning the ribosome with the start codon.

59

What is the ribosomal binding site rich in?

A /G rich region about 10 bases upstream of the start codon

60

What is the codons for mixed spel-xbal restriction site?

TACTAGATG

61

What happens if a start codon followed the mixed spel-xbal restriction site codon?

RBS would be significantly disturbed