Genetic Code

Question 1

How many hydrogen bindings are between A-T and G-C?

Answer 1

Two hydrogen bonds between adenine and thymine and three hydrogen bindings between guanine and cytosine

Question 2

What is degenerate or redundancy of genetic code?

Answer 2

Each amino acid may be encoded by more than one codons.

Question 3

What are the stop codons and start codons?

Answer 3

UAG,UGA,UAA- stop codons

AUG-methionine-start codons.

Question 4

How many RNA polymerase are present in prokaryotic and eukaryotic transcription?

Answer 4

Only one RNA polymerase in prokaryotes with 5 subunits.

Three RNA polymerase in eukaryotic transcription with more than 10 subunits

Question 5

What are the 5 subunits of RNA polymerase and what are they called?

Answer 5

Alpha, alpha, beta, beta prime, sigma

They are called Holoenzymes.
Apart from sigma, the other 4 makes up the core enzyme.

Question 6

What is the promoter sequence for initiation of prokaryotic transcription ?

Answer 6

Two promoter sequences- at -35 and -10.

-35=TTGACA
-10=TATAAT
Sigma binds at -35 sequence and DNA unwinds at -10

Question 7

What are the termination processes of prokaryotic transcription?

Answer 7

Rho dependent and rho independent termination

Question 8

What involves in the initiation of transcription in prokaryotes?

Answer 8

mRNA, DNA template strand, RNA polymerase and transcription factors.

Question 9

What are three types of polymerases in eukaryotic transcription?

Answer 9

Polymerase 1- encodes all rRNA except 5S rRNA. Insensitive to alpha armenitin

Polymerase2- encodes mRNA that encodes proteins, incredibly sensitive to alpha amenities

Polymerase 3- encodes 5S rRNA and tRNA and small nuclear rRNA

Question 10

What are the promoter sequence of RNA polymerase 2 in Eukaryotic transcription.

Answer 10

TATA box, also CAAT box or even an Octamer box in the upstream

Question 11

What are the promotor sequence of polymerase 2 and 3?

Answer 11

Polymerase 1-Two C-G rich regions in the -45 to +20 region.

Promotors from -180 to- - 105 enhances the transcription.

Polymerase 3-promotors that occur within the gene

Question 12

What is the difference between prokaryotic and ukaryotic transcription regarding DNA unwinding?

Answer 12

Eukaryotes have mass of DNA and proteins called chromatin. Nucleosomes need unwinding by FACT- facilitate chromatin transcription .

Question 13

What are terminator for various eukaryotic transcription by polymerase 1,2 and 3.

Answer 13

Polymerase2- elongation of nucleotide by 1000-2000 beyond the end of the gene being transcribed.

Polymerase 1- 18 nucleotide sequence: specific termination signals

Polymerase 3- hairpin like in rho independent termination in prokaryotes

Question 14

Does post transcriptional modification happens in both eukaryotes and prokaryotes?

Answer 14

No. Only in eukaryotes, and hence increase the life span of the mRNA.

Question 15

What are included in mRNA processing of eukaryotes?

Answer 15

1. 5’capping
2. 3’ poly A tail
3. excision of introns

Question 16

What is splicing carried out by?

Answer 16

By spliceosomes and other proteins such as small nuclear rRNA.

Question 17

What are included in pre rRNA and pre tRNA processing?

Answer 17

Methylation, excision of introns

Question 18

What are the small and large subunits of ribosomes in prokaryotes and eukaryotes?

Answer 18

Prokaryotes- small subunit-30 S+ ;large subunit 50 S\ Total-70 S

Eukaryotes-small subunit- 40S+ large subunit-60 S total- 80S

Question 19

What binds to the small and large subunits of ribosomes respectively;

Answer 19

mRNA to the small subunit and tRNA to large subunit

Question 20

What other organelles other than nucleus have their own ribosomes?

Answer 20

Chloroplast and mitochondria

Question 21

What is the function of amino act tRNA synthase?

Answer 21

Links the correct amino acid to the tRNA. By hydrolysis of ATP

AMP+A/A= activated amino acid———> let go of AMP and transfer the amino acid to tRNA

Question 22

What is the promotor sequence of translation in prokaryotes and eukaryotes?

Answer 22

Prokaryotes-shine dalgarno sequence

Eukaryotes- 5’ capping

Question 23

How does release factors (which recognize stop codon) terminate translation?

Answer 23

By adding water molecules to the growing polypeptide chain.

Question 24

Which molecule assists in protein folding?

Answer 24

Chaperones