Question

For each of the following sequences, state which process, DNA replication, transcription, RNA processing, or translation, is affected most directlyby deleting the sequence below. You should chose only one process for each sequence. (Section 15.4)

a. ori site

b. 3' splice site

c. poly(A) tail

d. terminator

e. start codon

f. –10 consensus seq

g. Shine-Dalgarno

Answer 1

Ans.

1). Ori

• Origin of replication (ori) and it's control elements form the replicon.
• DNA replication starts at ori, allowing the reproduction of a plasmid.
• DNA replication will be affected heavily upon deletion of ori.

2). 3' splice site

• RNA splicing is an important step for converting a pre-mRNA into a mature mRNA.
• This is a form of RNA processing which results in removal of introns and merging of exons.
• Any disturbance or deletion of 3' splice site may affect RNA processing.

3). Poly(A) tail

• Poly(A) tail addition to an mRNA is known as polyadenylation.
• Poly(A) tail is an mRNA stretch consisting only of adenine bases.
• It is a process which produces mature mRNA from pre-mRNA for the translation.
• Deletion of poly(A) tail will affect the translation process.

4). Terminator

• It is the DNA sequence which triggers RNA polymerase to stop transcription.
• It is that DNA region which includes the sequence coding for mRNA rho binding site and also the actual stop points of transcription.
• Upon deletion of terminator, process of transcription will be affecetd heavily.

5). Start codon

• It is the mRNA transcripts first codon which a ribosome translate.
• Start codon marks the site of initiation of protein synthesis.
• Deletion or damage of start codon will affect the process of translation.

6). –10 consensus seq

• DNA sequence at which protein binding occurs to initiate the transcription of a single mRNA from the DNA is known as the promoter.
• These are located near a genes transcription start site and may be 100-1000 base pairs long.
• Deletion of –10 consensus seq will result in a damaged transcription process.

7). Shine-Dalgarno

• It is a binding site for ribosomes in bacterias mRNA.
• Also found in trascripts of some chloroplast and mitochondria.
• It helps in the begining of protein translation by aligning ribosome with start codon.
• Any damage or deletion of SD sequence will consequently affect translation process also.