Inheritance in Humans

Two types of human chromosomes:

Autosomes & sex chromosomes.

Human somatic cell consists of:

44 autosomes & 2 sex chromosomes.

The function of Autosome:

Controls all characteristics of somatic cells.

The function of sex chromosome:

Consist of genes that determine gender.

Karyotype

The number & structure of chromosomes present in a cell nucleus.

Karyotype of a male with Down syndrome :

A total of 47 chromosomes which is 45 + XY.

Turner syndrome karyotype:

A total of 45 chromosomes which is 44 + XO.

Klinefelter syndrome karyotype:

A total of 47 chromosomes which is 44 + XXY

Sex-linked gene

Genes located on sex chromosomes which control specific characteristics but are not involved in sex determination.

Colour blindness caused by:

Recessive allele found in the X chromosome.