Chromosomal type-genetic basis of sex determination, Biology

Chromosomal Type-Genetic basis of Sex Determination

It refers to the condition where the genes involvcd in sex dcterrnincltion arc located on specific chromosomes known as the sex chromosomes.

First, we shall see how the genic typc of sex determination evolved into a chromosomal type of sex determination mechanism. In the primitive forms, the only difference between the two sexes was in their gametes. Later in evolution, morphological or phenotypic differcnce developed in the two sexes of a species.

In primitive forms, sex determination was due to genes on autosomes (the genic type). In the process of evolution, gradually, the genes responsible for sex determination got localised on specific chromosomes - the sex chromosomes, These chromosomes were designated as 'X' and 'Y' or 'Z' and 'W', and they can usually bc distinguished morphologically from eacb.other. The remaining chromosomes of the complement are known as. 'autosomes' and are designated 'A'.

The X and Y chromosomes differ from each other in many respects. This is because, there is accumulation of sex determining genes on tlie respective sex chromosomes. Also, there is negligible crossing-over between the X and Y chromosomes. This helps to preserve gene combinations favouring distinct sexual differences. The consequence is that the Y chromosome bears mostly the genes essential for the male determination while all the other genes become inert. These regions got reduced in size in some species and are completely lost in others. This was how the heteromorphic sex chromosome evolved.

Posted Date: 12/11/2012 4:36:57 AM | Location : United States







Related Discussions:- Chromosomal type-genetic basis of sex determination, Assignment Help, Ask Question on Chromosomal type-genetic basis of sex determination, Get Answer, Expert's Help, Chromosomal type-genetic basis of sex determination Discussions

Write discussion on Chromosomal type-genetic basis of sex determination
Your posts are moderated
Related Questions
What differences would you expect to see among pea seedlings grown for 10 days in total darkness and pea seedlings grown in the light for the similar period of time?   The s

What is inflammation? Inflammation is the initial response of the unspecific defense system versus aggressions against the body (the aggressions might be caused by infectious p

Carrier Based Gutta percha Removal “therma-fill” If the cone the carrier is metal and has cutting flutes that are engaging lateral dentin the instrument retrieval system (IRS)

Classification in terms of reservoir host 1.  Anthropozoonoses: Infections transmitted from lower vertebrate to man, e.g., rabies, plague, leptospirosis, etc. 2.   Zooanthro

L YMPH A TI C SYSTEM As 'Middle man' of circulation it mediates exchange between blood and the tissue. It is also a collecting system like venous system. Basically 'o

Tr aumatic reticuloperitonitis (TRP) It is also known as traumatic gastritis, hardware disease or traumatic reticulitis. Et i o l o g y : Frequentl



Anima l Nutrition Nutrition is the procurement of substances necessary for growth, maintenance and activities of a living body. The substances used for nutrition are called

In the preceding section we emphasised the fact that cvolution or the continuous adaptations to the environment can take place only when pheiiotypes exhibit variability. In the abs