Mutation Lecture 11 By Ms. Shumaila Azam Genomics Mutation Lecture 11 By Ms. Shumaila Azam

Mutation Changes in the nucleotide sequence of DNA May occur in the somatic cells These mutations may not pass to the off springs May occur in gametes (ova and sperm) These mutations may pass to the off springs

Are mutations helpful or harmful??? Mutations happen regularly Almost all mutations are neutral Chemicals and UV radiations can cause mutations Many mutations are repaired by enzymes

Some type of skin cancer and leukemia result from somatic mutations. Some mutations may improve an organism’s survival(beneficial).

Classes of mutation Spontaneous mutation Induced mutation

Spontaneous mutation They are caused during the DNA replication or by incorporation of incorrect nucleotide in the growing DNA chain. They occur naturally by changes in DNA sequences during replication.

Induced mutations These mutations are caused by the changes in the DNA brought about by some environmental factor called mutagens. E.g. UV rays, X-rays, gamma rays etc.

Types of mutation Chromosome mutation Gene mutation

Chromosomal mutation Changing the structure of chromosome The loss or gain a part of a chromosome

Types Deletion Inversion Translocation Non disjunction Duplication

Translocation It involves two chromosomes that are not homologous. Part of one chromosome is transferred to another chromosome.

Non disjunction Failure of chromosomes to separate during meiosis. Causes the gametes to have too many or too few chromosomes. Disorders Klinefelter’s syndrome-XXY chromosomes Down syndrome- three 21st chromosomes Turner syndrome- single X chromosome

Gene mutation Change in the nucleotide sequence of a gene May only involve a single nucleotide May be copying errors, chemicals, viruses

Types of gene mutation Point mutations Substitution Insertion Deletion Frameshift

Point mutation Change of a single nucleotide Include insertion deletion, substitution of one nucleotide in a gene.

Point mutation Sickle cell disease is the result of one nucleotide substitution Occurs in the hemoglobin gene

Frameshift mutation Inserting or deleting one or more nucleotides Changes the reading frame like changing a sentence Proteins built incorrectly