• In man there are 46 chromosomes
• The first  23^rd  pairs carry genes for body characters and are called autosomes
• The  23^rd  pair carry genes that determine the sex of a child and are called sex chromosomes
• The inheritance of sex chromosomes will determine whether we are a male or female
• The sex chromosome in male  conprises and « X » and a « Y » chromosome while the sex chromosomes in female comprise two identical X-chromosomes.
• Male therefore have the genotype « XY » while female has the genotype « XX »
• Male produces two types of sperm in equal ration, 50% carrying the x-chromosome and 50% carriying the y-chromosome. Male are therfore said to be heterogametic because the produce different kinds of gametes
• The female produce one kind of egg will all carying the x-chromosomes. They are therfore said to be homogametic
• The sex of a child is determine primarily by probabilities or chance and depends on the kind of sperm that fertilises the egg.
• If a sperm carrying the x-chromosomes fertiliese the egg, a female child re »sult i.e X(sperm) + X(egg) =XX(female offspring)
• If a sperm carrying the Y-chromosomes fertilise the egg(X) a male child will result
• Therfore there is an equal probability or chance of producing a male child or a female child

CO-DOMINANCE

This is a situation whereby a single characteristic or threat is controlled by 2 or more allele and none of the allele is ressecive to the other

That is the allele always expressed themselves equally. The human blood gray is called by 3 allele we have A,B, and O the allele A and B codominant that is they express thier 

selves equally when presented in an individual allele O is recessive to A and B this human present or have blood group which

Example 1 The seed resulting from a cross between white and alusite flower and a red and alusite flower gave a generation of pink flowers explain with the aaid of appropriate symbols and diagram what do you expect the next generation of flowers to be if in the pink were to be pollonated

Solution

Let the allele white= WW

Let allele alusite= RR

Parental phenotype= WW, RR