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Y1 IMS- Nucleic Acids > 2 Transcription Translation And Trafficking > Flashcards

2 Transcription Translation And Trafficking Flashcards

(78 cards)

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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
Which C bases are methylated
Ones outside of the CpG island
26
What is the effect of methylating
It suppresses their expression
27
Give an example of when CpG methylation suppressing gene expression
In X inactivation
28
For genes which are expressed, is the CpG island methylated?
Nopeeee
29
In inactive genes, is the CpG island methylated
Yes - as it suppresses their expression
30
What is transcription
A process by which DNA is copied into RNA
31
What are the three sections of transcription
Initiation Elongation Termination
32
Give a summary of the main steps in transcription
- 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
What is translation
Process by which mRNA is decoded to build a specific protein
34
Where does translation occur
Ribosome
35
Give a summary of the main steps of translation
- 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
Which enzyme separates the two strands of DNA during transcription
RNA polymerase
37
Which enzyme adds new complementary bases in transcription
DNA polymerase
38
Function of DNA polymerase in transcription
Adds new complementary bases
39
Purpose of 5’ cap
Protects the transcript from being broken down | Helps the ribosome attaches to the mRNA and start to make a protein
40
Purpose of poly A tail
The poly-A tail makes the RNA molecule more stable and prevents its degradation.
41
What is the polyadenylation sequence
AAUAAA
42
What is the poly A tail made up of
100- 200 adenosine nucleotides
43
What is RNA splicing
Introns get removed by RNA spliceosome
44
Function of the spliceosome in transcription
Removes introns | Pastes exons together
45
Give 3 differences between RNA and DNA
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
Which nucleotide does the splice site contain at the 3G’ end upstream
G-U dinucleotide at 3’ end
47
Which dinucleotide does the splice site contain at 5’ downstream of intron
A-G dinucleotide at 5
48
Which mRNAs do not have a poly(A)tail added
Histones
49
Which part of the ribosome is the growing peptide chain in
P site
50
Are adenine and guanine purines or pyrimidines
Purines
51
Are thymine cytosine and uracil purines or pyrimidines
Pyrimidines
52
What happens before a poly(A)tail is added
Cleaves mRNA - 20 nucleotides cleaved and then poly(A)tail added
53
Which enzyme adds a poly(A)tail
Poly(A) polymerase
54
What is polycistronic mRNA
MRNA which codes for several proteins involved in carrying out a particular task
55
What is an Operon
An operon is a cluster of functionally-related genes that are controlled by a shared operator.
56
What is alternative splicing
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
What is a protein isoform
Same function but slightly different aa sequence
58
Function of LCR - Locus Control Region
Regulates transcription of genes and enhances gene expression
59
What are the three stop codons
UAA UAG UGA
60
What is the start codon
AUG
61
Structure of tRNA
Shaped like a clover leaf with: - a 3’ end - a 5’ end - T loop - D loop - anticodon loop
62
What happens at the 3’ end of the tRNA
Amino acid attached via aminoacyl synthetase
63
Which enzyme attached the amino acid to the 3’ end of tRNA
Aminoacyl tRNA synthetase
64
Role of aminoacyl synthetase
Enzyme which attaches aa to 3’ end of tRNA molecule | Specific enzyme per tRNA which ensures that the correct tRNA is inserted
65
Role of the T loop of a tRNA molecule
Act as a recognition site for ribosome to form a ribosome tRNA complex
66
Which part of the tRNA molecule forms a tRNA- ribosome complex
T loop
67
What does the anticodon loop on a tRNA molecule form
H-bonds with complementary codon on mRNA
68
What is wobble base pairing
1st nucleotide on anticodon of tRNA can pair with different bases in 3rd position of mRNA codon
69
Usually, tRNA molecules are specific to amino acids so why do cells synthesise less tRNA than expected
A single tRNA can recognise multiple codons - (in wobble base pairing)
70
Give an effect of Wobble base pairing
Non-complementary base pairing can occur
71
What is Watson Crick base pairing
- Purines pair with pyrimidines - complementary base pairing - C with G - A with T - A with U
72
Example of non-complementary base-pairing: yeast tRNA for phenylalanine can recognise which two codons
UUC and UUU
73
In translation, why might the initiation factor ignore AUG codons
They are seen as ‘bad’/ not in good context
74
What are the three sites in the ribosome
E P A
75
What happens in translation when the ribosome reached the stop codon
release factors bind & polypeptide chain released from ribosome in cytosol
76
What is non-sense mediated decay
Premature stop codon via mutation in mRNA – mRNA exposed & degrades downstream of stop codon
77
Describe the structure of a ribosome briefly
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
What two things is a ribosome made of
Protein and rRNA

Y1 IMS- Nucleic Acids (4 decks)

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