Chromosomes-Heterozygous -Variation or change in the genetic material-

Chromosomes

•Chromosomes are the means by which the genes are transmitted from generation to generation.

• The exact location of a gene on a chromosome is known as its locus, and the array of loci constitutes the human gene map.  

•Homologous copies of a gene are termed alleles.

•If alleles are truly identical, their coding sequences and the number of copies do not vary, so the individual is homozygous at that specific locus.

•However, if the DNA is analyzed using either restriction enzyme examination or nucleotide sequencing, then, despite having the same functional identity, the alleles would be viewed as different and the individual would be heterozygous for that locus.  (not to differences in the protein products).Heterozygous 

•A heterozygous individual or genotype frequently results when different alleles are inherited from the egg and the sperm, but it may also occur as a consequence of spontaneous alteration in nucleotide sequence that results in a mutationVariation or change in the genetic material 

•The variation or change in the genetic material (Mutation) could occur at the gene level  or at the chromosome level.

•At the gene level it is called mutation or gene mutation

• at the chromosome level it is called chromosomal Aberration (Chromosome mutations) and involving whole chromosomes or parts of chromosomes

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