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

Protoplasmic streaming and tubular peristaltic flow model, Protoplasmic Str...

Protoplasmic Streaming and Tubular Peristaltic Flow Model The first of the above two models involves the well known phenomenon of cytoplasmic streaming in giant algal cells. C

Prawn, green gland in prawn

green gland in prawn

Cerebrum, what term is used to indicate its grooves?

what term is used to indicate its grooves?

Saturated fatty acids, Saturated Fatty Acids - These are solid at ro...

Saturated Fatty Acids - These are solid at room temperature. These are metabolically less active so have a tendency to deposit in the body (synthesized in body) These

Mention the role o ribosome in peptide, Mention the role o ribosome's in pe...

Mention the role o ribosome's in peptide -bond formation .How does ATP facilitate it? a) Of springs derived by asexual reproduction are known as clones. Justify giving two R

What is fontan operation and modifications, What is Fontan Operation and Mo...

What is Fontan Operation and Modifications ? Earlier reported to have 20 per cent mortality, it has come down to five per cent in specialized centres. In the earlier series th

Control of radio-pollution , (i)        Area uses or perm...

(i)        Area uses or permit exposure to radiation should be Marked' Restricted Area 'or Radiation zone etc. (ii)        Avoid x-rays of chest and lower back in routine physic

Pyramid of energy - ecological pyramids, Pyramid of Energy - Ecological Pyr...

Pyramid of Energy - Ecological Pyramids When we wish to compare the functional roles of the trophic levels in an ecosystem, an energy pyramid is probably the most informative.

Physiology of digestion, PHYSIOLOG Y OF DIGESTION Food - omnivorous. D...

PHYSIOLOG Y OF DIGESTION Food - omnivorous. Digestion - Intercellular. (i) Mechanical - by chewing, deglutinationm, churnning, peristalais. Under control of medulla oblonge

Vitamin - e, VITAMIN - E Also known as beauty vitamin / tocopherol ...

VITAMIN - E Also known as beauty vitamin / tocopherol / antisterlity vitamin . Antioxidant because it inhibits peroxide formation. It stops undesired oxidation. It

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