4.1 chromosomes, genes, alleles and mutations

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