RNA synthesis

Question 1

Main function of transcription and does the language remain the same?

Answer 1

mRNA synthesised in the nucleus and same language of nucleic acids

Question 2

Main function of translation and does the language remain the same

Answer 2

Protein production from mRNA

Different language form nucleic acid to protein

Question 3

How many nucleotides are there in the human genome?

Answer 3

3.2 x10^9

Question 4

How many homologs do chromosomes have and what are they referred to as?

Answer 4

2 and they’re known as paternal and maternal homologs

Question 5

What is the key function of chromosomes?

Answer 5

To carry genes

Question 6

What are centromeres made up of and what is there key function?

Answer 6

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

Question 7

Where are telomeres located and what is there main function?

Answer 7

○ Located at the end of the chromosome
○ Double strand
○ Six base pair repeat

Protects end of chromosome by preventing fusion from neighbouring chromosomes

Question 8

How many autosomes and sex chromosomes are there?

Answer 8

22 autosomes

1 sex chromosome

Question 9

What is the intergenic region and what does it contain?

Answer 9

The region of DNA between genes which have no current function

    Contains pseudo genes
Repetitive DNA

Question 10

What is a gene and its properties such as size and its affect on phenotype?

Answer 10

• Unit of heredity, contains instructions for an organisms phenotype
• DNA segment containing instructions for making a particular product
• Differ in size
• Differ in number of introns and exons
• Cluster into families

Question 11

What is the promoter?

Answer 11

a region involved in ensuring RNA polymerase combining for transcription.

Question 12

What does RNA make and what does it catalyze?

Answer 12

• DNA transcribed into RNA

* Catalyses the formation of phosphodiester bonds

Question 13

Types of RNA polymerase

Answer 13

• RNA polymerase 1- Most ribosomal RNA
• RNA polymerase 2- Protein coding, microRNA
• RNA polymerase 3- tRNA, 5S rRNA

Question 14

During RNA synthesis, how many bases are transcribed roughly?

Answer 14

• About 1.25-1.75 kb per min so quite fast

Question 15

During RNA synthesis, how do polymerases work and the effect on the number of transcripts from a gene simultaneously?

Answer 15

• Many polymerases work on the same gene

* Many transcripts from a gene simultaneously

Question 16

Why are Transcription factors required?

Answer 16

• Required to initiate or regulate transcription

Question 17

What does the promoter contain to which RNA polymerase 2 binds to and how many bp is it?

Answer 17

Containts TATA box which is 30 bp.

Question 18

Transcription(Initiation)

Answer 18

• Eukaryotic promoter regions contain a DNA sequence called the TATA box
• Transcription factor (TFIID ) sub unit, the TBP, recognises the TATA box and binds.
• The binding of TFIID enabled the adjacent binding of TFIIB and TFIIA.
○ TFIIB is responsible for linking RNA polymerase to the complex
○ TFIIA stabilises the complex
• TFIIF is already associated with the RNA polymerase when RNA polymerase binds to the TFIIA-TFIIB-TFIID complex.
• TFIIE and TFIIH both associate with RNA polymerase and initiation is complete.
○ TFIIH breaks apart the double helix at the transcription starting point
○ TFIIH also phosphorylates RNA polymerase II, so it can start transcription.

Question 19

Transcription(Elongation)

Answer 19

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

Question 20

Transcription(Termination)

Answer 20

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

Question 21

What are untranslated regions and what are they required for?

Answer 21

• Are transcribed but not translated as they’re required for regulation

Question 22

what is the 5 Primer UTR responsible for?

Answer 22

involved in the regulation of translation

Question 23

What is the 3 primer UTR responsible for?

Answer 23

regulation of mRNA stability and miRNA binding

Question 24

RNA processing(Capping)

Answer 24

• Capping:
○ 5’ end becomes modified after 25 nucleotides of RNA have been synthesised.
§ A guanine is added to the 5’ end and an enzyme called methyl transferase, methylates guanine to give rise to 7 methylguanine cap.
□ This cap protect the degradation of mRNA

Question 25

RNA processing(Polyadenylation)

Answer 25

• Polyadenylation:
○ 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 RNA in the cytoplasm as it moves out the nucleus.
○ The longer the poly-A tail the more stable the RNA is

Question 26

What is capping and polyadenylation required for?

Answer 26

Required for stability

Question 27

What is RNA splicing

Answer 27

Removal of introns and joining of exons

Question 28

Splicing

Answer 28

• 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 29

What is alternative splicing?

Answer 29

There are splice variables meaning during translation different proteins are synthesised