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y1 ims- nucleic acids > 2 Transcription Translation And Trafficking > Flashcards

2 Transcription Translation And Trafficking Flashcards

1
Q

Where in the cell is pre mRNA produced

A

Nucleus

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2
Q

What are nuclear pores made of

A

2 nuclear membranes

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3
Q

Where is mRNA translated

A

Cytosol

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4
Q

What is a poly some

A

mRNA molecules in cytosol covered in ribosomes

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5
Q

Function of the ER and Golgi apparatus

A

Used for packaging and secretion of proteins

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6
Q

Lysosome function

A

Degrade molecules imported into the cell and old/damaged cellular components

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7
Q

What are lysosomes made of

A

Degradative enzymes

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8
Q

Where are nuclear proteins synthesised

A

Cytosol

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9
Q

Where are nuclear proteins transported into

A

Nucleus via the nuclear pore

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10
Q

What is cytosol

A

Fluid part of cytoplasm

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11
Q

Function of nuclear proteins

A

They have amino acids sequences that tag proteins to be imported into the nucleus

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12
Q

What happens in mitochondria

A

Site of energy production - ATP is made

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13
Q

Function of RNA polymerase 1

A

Synthesis rRNA

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14
Q

Function of RNA polymerase 2

A

Synthesises mRNA, microRNA, and other non-coding RNAs

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15
Q

Function of RNA polymaerase 3

A

synthesises tRNA, rRNA and other small RNAs

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16
Q

What is the TATA box and what’s its function

A

A promoter region in eukaryotes- short run of T and A bases which varies slightly from gene to gene
Transcription factors bind to it

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17
Q

Location of the TATA box

A

25 to 35 base pairs upstream from the start of transcription

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18
Q

Why are T and A bases used in TATA box

A

They form the lowest energy bonds which are easiest to break - only 2 hydrogen bonds

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19
Q

Which enzyme binds to the TATA box

A

RNA polymerase 2

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20
Q

What is a CpG island

A

Stretches of DNA where there are a lot of C followed by G bases repeatedly

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21
Q

Location of CpG Islands

A

Occur upstream of many genes

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22
Q

In what way is a CpG island similar to a TATA box

A

It also has promoter activity

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23
Q

What does the p in CpG islands indicate

A

There is a phosphodiester bond between the C and G bases

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24
Q

Can a CpG island be present as well as a TATA box

A

Yes

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25
Q

Which C bases are methylated

A

Ones outside of the CpG island

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26
Q

What is the effect of methylating

A

It suppresses their expression

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27
Q

Give an example of when CpG methylation suppressing gene expression

A

In X inactivation

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28
Q

For genes which are expressed, is the CpG island methylated?

A

Nopeeee

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29
Q

In inactive genes, is the CpG island methylated

A

Yes - as it suppresses their expression

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30
Q

What is transcription

A

A process by which DNA is copied into RNA

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31
Q

What are the three sections of transcription

A

Initiation
Elongation
Termination

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32
Q

Give a summary of the main steps in transcription

A
  • RNA polymerase binds to promoter region (eg TATA box)
  • RNA polymerase separates the DNA strands
  • DNA polymerase adds complementary bases to the template strand (Uracil instead of thymine)
  • terminators signal that RNA transcript is complete
  • pre-mRNA is made
  • 5’ cap added
  • poly A tail added to 3’ end
  • splicing
  • spliceosome pastes exons together
  • mature mRNA formed
33
Q

What is translation

A

Process by which mRNA is decoded to build a specific protein

34
Q

Where does translation occur

A

Ribosome

35
Q

Give a summary of the main steps of translation

A
  • tRNA bound to methionine attaches to small ribosomal unit
  • this binds to 5’ end of mRNA and goes along
  • when it reaches the AUG (start codon) it binds to the large ribosomal subunit too
  • methionine starts in P site
  • another amino acid attracted to tRNA enters A site
  • bond formed between the two aa
  • both move along one, one goes to the exit site
  • a site gets empty so can hold next tRNA with aa
  • Stop codons recognised by release factor
  • Protein released
  • aa deletion
  • protein folding
36
Q

Which enzyme separates the two strands of DNA during transcription

A

RNA polymerase

37
Q

Which enzyme adds new complementary bases in transcription

A

DNA polymerase

38
Q

Function of DNA polymerase in transcription

A

Adds new complementary bases

39
Q

Purpose of 5’ cap

A

Protects the transcript from being broken down

Helps the ribosome attaches to the mRNA and start to make a protein

40
Q

Purpose of poly A tail

A

The poly-A tail makes the RNA molecule more stable and prevents its degradation.

41
Q

What is the polyadenylation sequence

A

AAUAAA

42
Q

What is the poly A tail made up of

A

100- 200 adenosine nucleotides

43
Q

What is RNA splicing

A

Introns get removed by RNA spliceosome

44
Q

Function of the spliceosome in transcription

A

Removes introns

Pastes exons together

45
Q

Give 3 differences between RNA and DNA

A
  1. DNA has a double strand but RNA has a single strand
  2. RNA has uracil instead of thymine
  3. DNA has deoxyribose but RNA has ribose
46
Q

Which nucleotide does the splice site contain at the 3G’ end upstream

A

G-U dinucleotide at 3’ end

47
Q

Which dinucleotide does the splice site contain at 5’ downstream of intron

A

A-G dinucleotide at 5

48
Q

Which mRNAs do not have a poly(A)tail added

A

Histones

49
Q

Which part of the ribosome is the growing peptide chain in

A

P site

50
Q

Are adenine and guanine purines or pyrimidines

A

Purines

51
Q

Are thymine cytosine and uracil purines or pyrimidines

A

Pyrimidines

52
Q

What happens before a poly(A)tail is added

A

Cleaves mRNA - 20 nucleotides cleaved and then poly(A)tail added

53
Q

Which enzyme adds a poly(A)tail

A

Poly(A) polymerase

54
Q

What is polycistronic mRNA

A

MRNA which codes for several proteins involved in carrying out a particular task

55
Q

What is an Operon

A

An operon is a cluster of functionally-related genes that are controlled by a shared operator.

56
Q

What is alternative splicing

A

When splicing happens during transcription, there is slight variation in where exactly the splicing occurs= results in single gene coding for multiple different protein isoforms

57
Q

What is a protein isoform

A

Same function but slightly different aa sequence

58
Q

Function of LCR - Locus Control Region

A

Regulates transcription of genes and enhances gene expression

59
Q

What are the three stop codons

A

UAA
UAG
UGA

60
Q

What is the start codon

A

AUG

61
Q

Structure of tRNA

A

Shaped like a clover leaf with:

  • a 3’ end
  • a 5’ end
  • T loop
  • D loop
  • anticodon loop
62
Q

What happens at the 3’ end of the tRNA

A

Amino acid attached via aminoacyl synthetase

63
Q

Which enzyme attached the amino acid to the 3’ end of tRNA

A

Aminoacyl tRNA synthetase

64
Q

Role of aminoacyl synthetase

A

Enzyme which attaches aa to 3’ end of tRNA molecule

Specific enzyme per tRNA which ensures that the correct tRNA is inserted

65
Q

Role of the T loop of a tRNA molecule

A

Act as a recognition site for ribosome to form a ribosome tRNA complex

66
Q

Which part of the tRNA molecule forms a tRNA- ribosome complex

A

T loop

67
Q

What does the anticodon loop on a tRNA molecule form

A

H-bonds with complementary codon on mRNA

68
Q

What is wobble base pairing

A

1st nucleotide on anticodon of tRNA can pair with different bases in 3rd position of mRNA codon

69
Q

Usually, tRNA molecules are specific to amino acids so why do cells synthesise less tRNA than expected

A

A single tRNA can recognise multiple codons - (in wobble base pairing)

70
Q

Give an effect of Wobble base pairing

A

Non-complementary base pairing can occur

71
Q

What is Watson Crick base pairing

A
  • Purines pair with pyrimidines
  • complementary base pairing
  • C with G
  • A with T
  • A with U
72
Q

Example of non-complementary base-pairing: yeast tRNA for phenylalanine can recognise which two codons

A

UUC and UUU

73
Q

In translation, why might the initiation factor ignore AUG codons

A

They are seen as ‘bad’/ not in good context

74
Q

What are the three sites in the ribosome

A

E P A

75
Q

What happens in translation when the ribosome reached the stop codon

A

release factors bind & polypeptide chain released from ribosome in cytosol

76
Q

What is non-sense mediated decay

A

Premature stop codon via mutation in mRNA – mRNA exposed & degrades downstream of stop codon

77
Q

Describe the structure of a ribosome briefly

A

Smaller subunit fits into depression of surface of larger subunit .
Eukaryotes: large subunit = 60s. Small subunit=40s. —>80s
Prokaryotes: large subunit = 50s. Small subunit=30s. —>70s

78
Q

What two things is a ribosome made of

A

Protein and rRNA

y1 ims- nucleic acids (4 decks)

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