Genomics transmission of genetic information

Question 1

What does the sense strand have the same sequence as?

Answer 1

The sense strand has the same sequence as the mRNA molecule

Question 2

What is the antisense strand used for?

Answer 2

The opposite, antisense strand is used as the template to
generate this identical mRNA strand

Question 3

How is mRNA extensively modified after transcription?

Answer 3

-Capped at 5’ end
-Polyadenylated at 3’ end
-Introns removed

Question 4

What is the central dogma?

Answer 4

DNA–>RNA–>protein

Question 5

What happens in transcription?

Answer 5

1. Transcription begins with strand of DNA with the transcription unit, which is used to create the RNA
2. TFIID is a transcription factor, and a component of it called TBP, binds to the TATA box on the DNA. Other transcription factors like TFIIA and TFIIB will then attach.
3. This is in preparation for the successful binding of RNA polymerase
4. once RNA polymerase is bound, other transcription factors complete the mature transcription complex
5. ATP is reduced to ADP and pi which allows RNy synthase to synthesise an RNA strand from the DNA strand.
6. Once the end of the transcription unit is reached, the polymerase detaches and RNA formation is complete

Question 6

What does 5’ capping protect?

Answer 6

-Protects 5’ end from degredation

Question 7

What does 5’ capping facilitate transport into?

Answer 7

Facilitate transport into
cytoplasm

Question 8

What does 5’ capping enhance?

Answer 8

Enhance translation

Question 9

How many nucleotides are added in polyadenylation?

Answer 9

-50-250 nucleotides are added

Question 10

What is not translated in genetic transmission?

Answer 10

Not the cap, not the UTR, not the polyA tail, only the RNA from the coding exons is translated

Question 11

How is RNA read?

Answer 11

RNA “read” in threes = codons

Question 12

How many possible combinations are there from the 4 bases?

Answer 12

64 possible combinations of 4 bases

Question 13

What does a codon code for?

Answer 13

Codon → specific amino acid

Question 14

What does it mean by open reading frame?

Answer 14

Same nucleotide sequence can be used
differently

Question 15

Where does translation occur?

Answer 15

Cytoplasm

Question 16

What happens to mRNA in translation?

Answer 16

mRNA to protein

Question 17

What type of RNA is needed in translation and what does it carry?

Answer 17

Needs tRNA (transfer RNA)
-tRNAs carry amino acids

Question 18

What are tRNA specific to?

Answer 18

Specific to codon

Question 19

What do tRNA need?

Answer 19

-Needs initiation factors
-Needs elongation factors

Question 20

What are the steps involved in translation?

Answer 20

1. Translation initiation
2. Translation elongation
3. Translation Termination

Question 21

What happens in translation initiation?

Answer 21

1. mRNA binds to small subunit
   -Ribosome binding site sequence binds to a complementary sequence in an RNA molecule in the small subunit of the ribosome, with the help of protein initiation factors
2. Initiator aminoacyl tRNA binds to start codon
3. Large subunit of ribosome binds, completing ribosome assembly and translation begins

Question 22

What happens in translation elongation?

Answer 22

1. Incoming aminoacyl tRNA.
   -New tRNA moves into A site, where the anticodon base pairs with the mRNA codon
2. Peptide bond formation
   -The amino acid attached to the tRNA in the P site is transferred to the tRNA in the A site
3. Translocation
   -mRNA is ratcheted through the ribosome by elongation factors. The tRNA attached to the polypeptide chain moves into the P site. The A site is empty.
4. Incoming aminoacyl tRNA
   -New tRNA moves into A site, where the anticodon base pairs with the mRNA codon
5. Peptide bond formation
   -The polypeptide chain attached to the tRNA in the P site is transferred to the aminoacyl tRNA in the A site
6. Translocation
   -mRNA is ratcheted through the ribosome again. The tRNA attached to polypeptide chain moves into P site. Empty tRNA from P site moves to E site, where tRNA is ejected. The A site is empty again

Question 23

What happens in translation termination?

Answer 23

1. Release factor binds to stop codon
   -When translocation exposes a stop codon, a release factor fills the A site. The release factor breaks the bond linking the tRNA in the P site to the polypeptide chain
2. Polypeptide is released and ribosome subunits seperate
   -The hydrolysis reaction frees the polypeptide, which is released from the ribosome. The empty tRNAs are released either along with the polypeptide or when the ribosome seperates from the mRNA, and the 2 ribosomal subunits dissociate. The subunits are ready to attach to the start codon of another message and start translation anew.