RNA synthesis

Question 1

what is the main function of transcription?

Answer 1

for mRNA to be synthesised in the nucleus

Question 2

Does the language remain the same?

Answer 2

As the transcript goes from DNA to mRNA so contains the same language

Question 3

what is the main function of translation?

Answer 3

proteins are produced from mRNA

Question 4

Does the language remain the same?

Answer 4

Transcript of the mRNA produces the protein so therefore they contain different languages

Question 5

how many nucleotides are in the human genome?

Answer 5

3.2x10^9

Question 6

What are the two homologs found in chromosomes?

Answer 6

paternal and maternal

Question 7

what is the key function of chromosomes and what do they contain?

Answer 7

22 pairs of autosomes and 1 pair of sex chromosomes
centromere and telomere
pseudo genes

Question 8

centromere

Answer 8

is made up of DNA and key function is to keep the chromosome attached to the spindle fibre during mitosis

Question 9

telomere

Answer 9

located at end of chromosome
double stranded and a 6 pair repeat
protects end of chromosome by preventing fusion from neighbouring chromosomes

Question 10

what is the intergenic region?

Answer 10

region of DNA between genes which have no current function

Question 11

what is a gene and its properties?

Answer 11

unit of heredity - contains instructions for an organisms phenotype
DNA segment containing the formation of a particular product
differ in size
differ in number of introns and exons
cluster into families

Question 12

what is the promoter?

Answer 12

region/ DNA sequence to which RNA polymerase binds to the initiate transcription
cis acting element (only works on promoter region)

Question 13

what is the TATA box?

Answer 13

consists of 6 nucleotides; TATAAT
appears at -10 to -25 (upstream)
found in genes that are actviely transcribed by RNA

Question 14

What is TTAGACA?

Answer 14

-35 sequence
sequence recognised by delta factor
promoter region

Question 15

What does DNA transcribe into and what does RNA polymerase catalyse?

Answer 15

DNA transcribes into RNA and it catalyses the formation of phosphodiester bonds

Question 16

types of RNA polymerase

Answer 16

RNA polymerase I - most ribosomal RNA
RNA polymerase II - protein coding, microRNA, non coding RNA
RNA polymerase III - tRNA, 5S rRNA, other small RNAs

Question 17

how many bases are transcribed roughly during RNA synthesis?

Answer 17

about 1.25-1.75kb per min so quite fast

Question 18

how do polymerases work during RNA synthesis as well as their effect on the number of transripts from a gene simultaneously?

Answer 18

many polymerases work on the same gene

many transcripts from a gene simultaneously

Question 19

Why are transcription factors required and what does the promoter contain which RNA polymerase II bind to (how many bps are there)?

Answer 19

requierd to initiate or regulate transcription and contains TATA box (30 bps)

Question 20

transcription (initiation)

Answer 20

TATA box is recognized by the TATA binding protein (TBP), sub unit of transcription factor (TFIID) and binds distorting the DNA

This allows the binding of transcription factors, TFIIA (stabilizes the complex) and TFIIB (responsible for linking RNA polymerase to the complex) 

TFIIF is already associated with the RNA polymerase when the RNA polymerase binds to the TBP-TFIIB-TFIID complex 

Then other transcription factors TFIIE and TFIIH bind 

RNA polymerase II assembles at promoter: transcription initiation complex is formed 

TFIIH breaks apart the double helix at the transcription starting point  

It also phosphorylates RNA polymerase II, so it can begin transcription

Question 21

transcription (elongation)

Answer 21

RNA strand gets longer by the addition of nucleotides at the growing 3’ end

Question 22

transcription (termination)

Answer 22

when a sequence of DNA, known as a terminator and located after the stop codon, is reached transcription ends

Question 23

what are untranslated regions and what are they required for?

Answer 23

transcribed but not translated as they are required for regulation

Question 24

what is the 5 primer UTR responsible for?

Answer 24

involved in the regulation of translation

Question 25

what is the 3 primer UTR responsible for?

Answer 25

regulation of mRNA

stability and miRNA binding

Question 26

RNA processing (capping)

Answer 26

5’ end becomes modified after 25 nucleotides of RNA have been synthesized

a guanine is added to the 5’ end and an enzyme called methyl trasnferase, methylates guanine to give rise to 7 methylguanine cap 

the cap protects the degradation of mRNA

Question 27

RNA processing (polyadenylation)

Answer 27

mRNA is trimmed by an enzyme at the 3’ end

the transcript is finished off by a second enzyme that adds repeated adenine bases to the cut end 

Poly A tail is formed making the transcript more stable and protects pre- mRNA from RNAses which digests the RNA in the cytoplasm as it moves out the nucleus 

The longer the poly A tail, the more stable the RNA is

Question 28

what is AAUAAA?

Answer 28

cleavage signal recognised by endonuclease for the addition of poly(A) polymerase to form the polyadenylated tail

Question 29

why is capping and polyadenylation required? for?

Answer 29

required for stability

Question 30

what is an exon and intron?

Answer 30

exon - segment of genetic information in genome

intron - intervenes between exons and doeasnt contribute to genetic information to be used in final product

Question 31

what is RNA splicing?

Answer 31

removal of introns and joining of exons

Question 33

splicing

Answer 33

• Special sequences in a pre-mRNA signal the beginning and the end of an intron Recognised by snRNPs
• At GU we have the 5 primer splicing region
• At AG we have the 3 primer splicing region
• The lariate structure loops to join the branch point as is disposed off leaving the exon which joins the second exon.

Question 33

what is alternative splicing?

Answer 33

there are splice variables meaning during translation different proteins are synthesised