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12.4 MUTATIONS I. Kinds of Mutations

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Presentation on theme: "12.4 MUTATIONS I. Kinds of Mutations"— Presentation transcript:

1 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

2 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

3 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

4 Gene Mutations: Substitution, Insertion, and Deletion

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

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

7 Chromosomal Mutations
Deletion Duplication Inversion Translocation

8 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

9 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

10 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

11 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.

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

13 Normal Female Karyotype

14 Normal Male Karyotype

15 Abnormal Karyotype-Trisomy #21
Down’s Syndrome

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

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