Recessive Sex Linked Inheritance

 

Sex linked genes reside in the X chromosome, The Y chromosome has no complement allele to pair up to, therefore the female will only carry one allele for a given characteristic this particular condition is referred to as hemizygous. When this hemizygous female is paired to a male she can only transmit one allele to just one of the male’s two X chromosomes which in turn makes him only a carrier of the particular character (heterozygous), when paired to a normal female he will only be able to pass the character to his daughters.

 

  Black Yellow Male      Yellow Brown Female

   Homozygous XX              Hemizygous XY

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   

Males carriers of Brown    Normal females

 

 

 

 

 

 

 

 

 

 

 

 

SEX LINKED FACTORS

 

            

(N,N) X (b Y )

Autosomes

 

Autosomes are all the non sex homologous chromosomes pairs, these homologous chromosomes have two gene alleles for each character, these characters may be recessive, dominant or codominant.

 

AUTOSOMAL CHARACTERS

 

:

 

 

Epistasis

 

Epistasis is a condition in which the interaction between two or more genes in a locus affects or masks the phenotypic expression of another gene.

Sex Chromosomes

Out of the +-84 chromosomes that a canary has, two are very different in their shape and size, they are X Y  for the female  The female’s Y chromosome is, as far as we now know  smaller  and devoid of significant

characters.

If we use the Punnet square

We will obtain the following

Results:

             50% Males

             50% Females

Linked Genes

 

When genes are located on the same chromosome they can not independently recombine or crossover, they are said to be linked.

Modifiers

 

Modifiers are secondary genes that modify the effect of other genes, they can alter phenotypic expression and cause variations to any characteristic, it may be a  multiallelic event usually difficult to pinpoint.

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