12.4 MUTATIONS I. Kinds of Mutations Mutations are changes in the genetic material A. Gene mutations – changes in a single gene 1. point mutation – changes in one or a few nucleotides

3 TYPES OF MUTATIONS a. substitution – one base is changed to another * usually affects only one amino acid b. insertion or deletion – a base is added or removed from DNA sequence

FRAMESHIFT MUTATIONS i. Insertion & Deletion are known as frameshift mutations because the reading frame of the genetic message is shifted when a base is added or removed ii. may change every amino acid that follows the point of mutation iii. can alter a protein so much that it can not function

Gene Mutations: Substitution, Insertion, and Deletion

CHROMOSOMAL MUTATIONS B. Chromosomal mutation – changes in the number or structure of chromosomes 1. Four types of chromosomal mutations: a. Deletion – all or part of chromosome is lost

CHROMOSOMAL MUTATIONS b. Duplication – produces extra copies of parts of a chromosome c. Inversion – reverses the direction of parts of chromosomes d. Translocation – part of one chromosome breaks off and attaches another chromosome

Chromosomal Mutations Deletion Duplication Inversion Translocation

MUTATIONS II. Significance of Mutations A. many mutations are neutral and have little or no effect on expression of a gene or function of protein 1. mutations allow genetic diversity in a species

MUTATIONS B. harmful mutations are the causes of many genetic disorders or even cancer beneficial mutations produce proteins that can be helpful in different environments

MUTATIONS Meiosis is a process where gametes (sex Cells) half the number of chromosomes. a. Nondisjunction occurs when a complete set of chromosomes fails to separate during Meiosis. gametes (sperm & egg) may produce triploid (3N) or tetraploid (4N) organisms

What happens if nondisjunction occurs? The gamete will die or result in conditions known as trisomy or monosomy. Trisomy - a person has more than 2 copies of the same chromosome. Monosomy – a person only has one copy of a chromosome.

How can you tell that? Take a picture of the chromosomes This is known as a karyotype.

Normal Female Karyotype

Normal Male Karyotype

Abnormal Karyotype-Trisomy #21 Down’s Syndrome

Abnormal Karyotype – Monosomy of the X chromosome Turner’s Syndrome