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

What are the symptoms of brown-sequard syndrome, What are the Symptoms of B...

What are the Symptoms of Brown-Sequard syndrome Symptoms of Brown-Sequard syndrome usually appear after an affected individual experiences a trauma to the neck or back. First s

Water-soluble vitamins for school children and adolescents, Determine Water...

Determine Water-soluble vitamins needs of school children and adolescents? The suggested requirements are given in Table 15.2 (ICMR 1990). Thiamine is computed as 0.5 mg/1000 K

Trophic structure-structure of community, Trophic structure Organisms i...

Trophic structure Organisms in a community are closely interrelated with each other through feeding relationships. Another aspect which is quite obvious in a community is th

Role of lymphatic system - circulation, Normal 0 false false ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Shifting attention by dopamine, Q. Shifting attention by Dopamine? Dopa...

Q. Shifting attention by Dopamine? Dopamine: Dopamine plays a pivotal role in aspects of shifting attention. Administration of D1/D2 receptor antagonist haloperidol impairs the

Explain tertiary and quaternary structure of proteins, Explain Tertiary str...

Explain Tertiary structure and Quaternary structure of proteins Tertiary structure Secondary structure, in turn, folds back and bonds to itself in a three-dimensional mann

Photosynthesis., C4 plants have higher net photosynthetic rate because ...

C4 plants have higher net photosynthetic rate because a.they have no photorespiration b.can photosynthesise in low in

Diabetes mellitus management after open heart surgery, Diabetes Mellitus Ma...

Diabetes Mellitus Management after Open Heart Surgery :  Diabetic patients undergoing coronary artery bypass surgery who are on oral hypoglycemic drugs are pre operatively s

Taxonomy, Agroup of realated genera are classified as-?

Agroup of realated genera are classified as-?

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