4.1 CHROMOSOMES, GENES, ALLELES AND MUTATIONS

Genetics

Eukaryote Chromosomes

Eukaryote chromosomes are made of DNA which is wound around proteins called histones.

Prokaryote chromosomes do not contain protein.

Definitions

Gene: A heritable factor that controls a specific characteristic.

Allele: One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same locus as other alleles of the gene.

Genome: The whole of the genetic information of an organism.

Mutations

Mutation: A change in the base sequence of a gene. Sickle cell anemia is an example of a disease which

is caused by a mutation on chromosome 11. It is a condition which causes pain, swelling, infections, kidney failure, gallstones, strokes and anemia.

Sickle Cell Anemia

In the sequence of bases, a GAG is mutated to a GTG which causes a glutamic acid to be replaced by valine. This is what causes a change in the hemoglobin protein and sickle cell anemia condition.

Ss = resistant to malaria ss = sickle cell anemia SS = normal