Gene mutatiorns, Biology

Assignment Help:

Gene or point mutations occur when the DNA sequence of a gene is altered and the new nucleotide sequence is passed on to the offspring. This occurs either due to addition or deletion or substitution of one or a few nucleoticles. Nucleotide substitutions can be either transitions or transversions. Transitions are replacements of a purine by another purine (A by G or vice versa) or a pyrimidiile by another pyrimidine (C by T or vice versa). Transversions are replacements of a purine by the pyrimidine or vice versa (G or A by C or T or vice versa). We will briefly explain the different types of gene mutations.

a) Substitutions : substitution of one base by another would result in an altered amino acid in a polypeptide chain. For instance triplet AAT in DNA (UUA in mRNA) would specify leucine. But if the first A is ieplaced by C, it will code for valine. Some of the codons are degenerate and substitutions may not alter the amino acid specified. For instance, in the triplet AAT if the first A is replaced by G the amino acid coded would still be leucine. Gene mutations which do not normally affect the active site of a protein will not alter its biological functions. But nucleotide substitutions that change a triplet coding lor an amino acid into a termination codon would produce adverse effects. Once again in AAT, if the second A is replaced hy T (An), the resulting rnRNA codon IJAA is a termination codon. When a termination codon is present in the middle of an mRNA molecule the subsequent codons are not translated and an incomplete polypeptide will be released from ribosomes.


Related Discussions:- Gene mutatiorns

Protonephridia and metanephridia, Protonephridia and Metanephridia Ne...

Protonephridia and Metanephridia Nephridia take place in two major forms - the protonephridium and metanephridium. Protonephridia are found in flat worms. The protonephridial

Effects of environmental disasters, Primary effects 1.      Nuclear con...

Primary effects 1.      Nuclear contamination 2.      Biological contamination 3.      Chemical contamination 4.      Destruction of infrastructure facilities. 5.

Infectious laryngotracheitis, I nfe c tio u s laryngotracheitis It...

I nfe c tio u s laryngotracheitis It is a slow, laterally spreading respiratory disease of chickens, pheasants, peafowl and turkeys caused by a herpes virus with high morb

List the types of gellan gum, List the types of Gellan gum.   The three...

List the types of Gellan gum.   The three types of gellan gums are: High acetyl gellan (partially deacetylated) Low acetyl gellan (highly deacetylated) High cl

What are plant cell vacuoles, What are plant cell vacuoles? What are their ...

What are plant cell vacuoles? What are their functions? How is the covering membrane of the vacuoles called? Ans) Plant cell vacuoles are cell structures delimited by membranes

Vaccines for gas infections, In developing countries because of poor compli...

In developing countries because of poor compliance, poverty, ignorance, primary and secondary prevention strategies are difficult to implement properly. Also in western countries (

Define traditional methods of food processing, Define Traditional Methods o...

Define Traditional Methods of Food Processing? Because food is so important to survival and most foods remain edible for only a brief period of time, people as the initial ages

What is heterophagic intracellular digestion, Heterophagic intracellular di...

Heterophagic intracellular digestion is the breaking into minute substances of external substances engulfed in the cell by pinocytosis or phagocytosis. Phagosomes or pinosomes fuse

Reproduction, write about asexual reproduction in mucor?

write about asexual reproduction in mucor?

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd