Question

   Slide 11 problem:

   5’ UGG 3’ -  mRNA

                      -Template DNA stand

  -Nontemplate DNA strand

Slide 33 problem:

The following sequence of nucleotides in a DNA strand was used as a template to synthesize a mRNA that was then translated into protein:

                        5’-TTAACGGCTTTTTTCCAT-3’

Predict the C-term aa and the N-term aa of the resulting polypeptide.

Slide 34 problem:

True or False? Explain your answer!

1.An individual ribosome can make only one type of protein.

2.The large and small subunits of an individual ribosome

always stay together and never exchange partners.

3.An mRNA may contain the sequence ATTGACCCCGGTCAA

Slide 35 problem:

A mutation in DNA generates a UGA stop codon in the middle of the mRNA coding for protein X. You are studying protein X and isolating it from mutated cells. Which one best describes your findings:

1. No changes whatsoever are found between protein X isolated from wild type and mutant cells
2. Protein X from wild type cells is shorter than the one from mutant cells
3. Protein X from wild type cells is longer than the one from mutant cells
4. Protein X from mutant cells has a new function

Answer 1

Ans slide 33..

TTA amino acid of 5' end is the N term and CAT of 3' end is C end.

The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide referring to the free amine group (-NH2) located at the end of a polypeptide. Normally the amine group is bonded to another carboxylic group in a protein to make it a chain, but since the end of a protein has only 1 out of 2 areas chained, the free amine group is referred to the N-terminus. By convention, peptide sequences are written N-terminus to C-terminus, left to right in LTR languages.[1] This correlates the translation direction to the text direction (because when a protein is translated from messenger RNA, it is created from N-terminus to C-terminus - amino acids are added to the carbonyl end).

Ans slide 34

1.False. Ribosomes can make any protein that is specified by the particular mRNA that they are translating. After translation, ribosomes are released from the mRNA and can then start translating a different mRNA.

2.False. Ribosomal subunits exchange partners after each round of translation. After a ribosome is released from an mRNA, its two subunits dissociate and enter a pool of free small and large subunits from which new ribosomes assemble around a new mRNA.

3.False. RNA contains uracil instead of thymine. So this sequence is not possible as it contains thymine.

Ans slide 35

(C) Protein X from wild type cells is longer than the one from mutant cells. As stop codon appears in the middle of the mRNA . Hence, protein formed will be short.