Mendelian inheritance

prep by : Mohamed abdukadir kalifMPhil in optometry

Basic concepts

1) Gene : is a sequence of nucleotide in DNA which is concerned in the formation of specific RNA

2) allele

• Special version of genes which are present on the homologues of the same loci.

• In simple words if there is a gene which represent the color of your eyes from your mother side , then there is same gene which represent the color of your eyes from the father side , these same genes from the mother and father side is called us alleles

3)Locus

• Specific position of homologues chromosome• One chromosome has many loci positions

4) Homologous

• these are similar chromosomes having similar set of genes or alleles which are inherited from the mother and father

5)phenotype

• You can not see the genes which determines the color of your eyes , but you can see the color of your eyes .

These manifestation of genes which can be observed are called phenotype

6) Genotype

• This is genetic information which is present at specific locus of homologues chromosome , which can not be seen on naked eyes

7)Dominant

• In simple words in the presence of healthier allele , when a defective allele (mutant gene ) can make abnormal phenotype

• So Most of the time the mutations of outosomal dominant occur in those genes which are responsible for the formation of structural proteins and regulatory proteins (receptors)

• In simple words the outosomal dominant mutant gains function , and that is what causes the manifestation of the disease , where the recessive mutants they lose function.

8)Recessive

• In simple words in the presence of healthier allele , when a defective allele (mutant gene) can not make abnormal phenotype .

• But in order a recessive trait be manifested (become phenotype) , both alleles should be mutant

• So mostly outosomal recessive occurs to those genes which are responsible for the formation of functional proteins (enzymes)

9)Heterozygous

• If two alleles at the same locus , are some what different from each other , these two homologues chromosome which are some what different from one another is called heterozygous

Compound Heterozygous

• Both alleles have abnormalities (mutants) but in different loci positions

to be continued