GENETICS 6

MUTATION

• Mutation is any change in DNA sequence.
• It is a heritable change.
• Mutations can affect genotype as well as phenotype.
• It also leads to variations.
• Types of mutations:
• 1. Gene mutation--  Point mutations, frame-shift mutations
• 2. Chromosomal mutation- change in no. Or change in structure.

Gene mutation

   A. ReplacementMutations that occur due to change in a single base pair of DNA is called as point mutations.

 For example: sickle cell anemia

 

• When there is deletion or insertion of base pairs of DNA, it causes frame-shift mutations.

• Mutagens are the chemical and physical factors that induce mutations. UV rays can also cause mutations.

GENETIC DISORDERS

• Analysis of traits in several generations of family is called pedigree analysis.
• Inheritance of a particular trait is represented in the family tree over generations.
• Symbols used in pedigree analysis

GENETIC DISORDERS

Two types

1. Mendelian

2. Chromosomal

MENDELIAN DISORDERS

• Occurs due to single gene changes

Follow the inheritance pattern suggested by mendal

Can be Dominant or Recessive

Can be autosomal or sex linked.

Inheritance pattern can be traced in a family by pedigree analysis

• Autosomal disorders – cystic fibrosis, sickle cell anaemia, myotonic dystrophy
• Sex-linked – haemophilia, colour blindness

• HAEMOPHILIA – 
• sex-linked recessive disease
• A single protein that is a part of the cascade of proteins involved in the clotting of blood is affected.
• In affected individual, a simple cut will result in non-stop bleeding.
• Heterozygous female (carrier) can transmit the disease to son.
• Possibility of female becoming a haemophilic is extremely rare.

COLOUR BLINDNESS

sex linked

Recessive