Human Genetics

Individuals with karyotype of 45 chromosomes(44 autosomes and one X chromosomes) have been found to be suffering from female gonadal dysgenesis or Turner's syndrome

In human beings, sex is determined by X and Y chromosomes.

Recessive gene is that, which produces its characteristic phenotype only when its allele is identical. It causes colour blindness.

Members of a pure genetic line are homozygous.

All the genes of a particular chromosomes comprise a genotype.

The scientist who pointed out for the first time that inborn errors of metabolism are controlled by hereditary factors, and are inherited in a Mendelian fashion was Garrod.

The genes which tend to be inherited together are linked genes.

The ABO blood group in human beings is a good example of multiple gene inheritance.

Y chromosome is (in humans and other mammals) a sex chromosome, which is normally present only in male cells, which are designated as XY. Y spots in the interphase nuclei give indications of the number of Y chromosomes.

The disease called phenylketonuria is caused by a defect in phenylalanine tyrosine metabolism. This is an example of congenital disease. Congenital disorder is present at birth.

The genetic abnormality called mongolism is an example of autosomal abnormality.

The abnormalities involving X chromosomes can easily be determined by analysing a structure in the nucleus of cells from the buccul mucosa, this structure is called barr bodies.

With respect to X-linked genes males are said to be hemizygous. Having some single copies of genes in an otherwise diploid cell or organism is hemizygous.

Amniocentesis is a technique used for the detection of genetic abnormalities. It is a process in which amniotic fluid is sampled using a hollow needle inserted into the uterus to screen for abnormalities in the developing fetus.

The pattern of inheritance of sex linked character haemophilia is called dygenic criss cross inheritance .

Certain traits such as baldness in human biings, which are actually determined autosomal genes but their expression being influenced by sex hormones are called sex influenced traits.