Essay Questions A portion of a specific DNA molecule consists of the following s

Question

Essay Questions A portion of a specific DNA molecule consists of the following sequence of nucleotide triplets. 1. TAC GGA CTT GGG TCC The DNA sequence codes for the following short polypeptide. methionineleucine- glutamic acid -proline-arginine Describe the steps in the synthesis of this polypeptide What would be the effect of a deletion or an addition in one of the DNA nucleotides? What would be the effect of a substitution in one of the nucleotides? a. b. c. Using the following sex-linked genotypes, show the cross in the Punnett Square, and then answer the questions that follow. 2. a. What proportion/percent of the male children are colorblind? b. What proportion/percent of the female children are colorblind?

Explanation / Answer

1. The sequence of DNA is : TAC GGA CTT GGG TCC

The synthesized polypeptide from the above DNA sequence is Met-Leu-Glu-Pro-Arg

a. The steps in the synthesis of the above polypeptide are

1. synthesis of mRNA from the above template- Transcription

The synthesized mRNA from the above DNA template is AUG CCU GAA CCC AGG

2. Post transcriptional modifications

3. synthesis of Polypeptide using the synthesized mRNA-Translation.

b. if a nucleotide is added to or removed from the starting of the DNA sequence, then entire polypeptide may get changed. If a nucletide is added to the end of the DNA sequence of the above given sequence then no change may occur in the sequence of the polypeptide. if a nucleotide is removed from the end of the nucleotide then only the last amino acid of the polypeptide sequence gets changed.

c. if only any one nucletide is substituted then that particular amino acid may or may not get changed, because each amino acid is coded by one to six codons. after substitution of amino acid also if that particular codon is coding for the same amino acid then the total sequence of that particular polypeptide and that particular amino acid will not get changed.

if change in the nucleotide causes change in the amino acid then it may cause change in the polypeptide sequence at that particular amino acid level.

it may even result in the termination of the synthesis of the polypeptide, as certain sequence of codons code for stop codons.

2. top gametes XB and XB and side from to down are Xb and Y

a. 100% of male children are color blind, because they do not have any recessive color blind gene on their Y chromosome.

b. 100% of female children are only carriers for color-blind, because one of their two X-chromosomes is carrying one recessive chromosome for color blind and other one for dominant.

XBXb XBXb XBY XBY

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