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Changes in DNA that affect genetic information MUTATIONS Changes in DNA that affect genetic information

2 Main Types of Mutations 1.) Chromosomal Mutations 2.) Gene Mutations

What are chromosomes? Humans have 23 pairs of chromosomes, with one chromosome from each parent. The chromosomes are coiled up DNA. Under normal conditions all of the chromosomes are inherited in tact. This is a normal karyotype of human chromosomes. A karyotype is a picture of chromosomes lined up to look at and compare.

Chromosomal Mutations Any change in the structure or number of chromosomes Large scale: Affect many genes

4 Types Deletion Duplication Inversion Translocation

One or more genes are removed Chromosomal Deletion One or more genes are removed Causes: Wolf-Hirschhorn syndrome (severe mental retardation) cri du chat syndrome (mewing sounds, mental retardation)

Chromosomal Duplication A segment of genes is copied twice and added to the chromosome Causes: Charcot–Marie–Tooth disease (high arched foot, claw feet, confined to a wheelchair)

Chromosomal Inversion a segment of genes flip end-to-end on the chromosome Causes: Four-Ring Syndrome (cleft pallate, club feet, testes don’t descend)

Chromosomal Translocation Material is swapped with another chromosome Causes: Burkitt’s Lymphoma (cancer of the lymph nodes, in children)

Chromosome Mutations Changes in number and structure of entire chromosomes Original Chromosome ABC * DEF Deletion AC * DEF Duplication ABBC * DEF Inversion AED * CBF Translocation ABC * JKL GHI * DEF

Gene Mutations Small scale: one gene is affected Any change to the DNA sequence of a gene: Nucleotides/Bases may be added, missing, or changed

Gene Mutations Point Mutations – changes in one or a few nucleotides Substitution THE FAT CAT ATE THE RAT THE FAT HAT ATE THE RAT Insertion THE FAT CAT XLW ATE THE RAT Deletion THE FAT ATE THE RAT

Point Mutation One base (A, T, C, or G) is substituted for another Causes: Sickle-cell anemia 3 Possible Consequences: nonsense mutations: code for a stop, which can translate the protein missense mutations: code for a different amino acid silent mutations: code for the same amino acid

Gene Mutations Frameshift Mutations – shifts the reading frame of the genetic message so that the protein may not be able to perform its function. Insertion THE FAT CAT ATE THE RAT THE FAT HCA TAT ETH ERA T Deletion TEF ATC ATA TET GER AT H H

Significance of Mutations Most are neutral Eye color Birth marks Some are harmful Sickle Cell Anemia Down Syndrome Some are beneficial Sickle Cell Anemia to Malaria Immunity to HIV

What Causes Mutations? There are two ways in which DNA can become mutated: Mutations can be inherited. Parent to child Mutations can be acquired. Environmental damage Mistakes when DNA is copied

Chromosome Mutations Down Syndrome Chromosome 21 does not separate correctly. They have 47 chromosomes in stead of 46. Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of inteligence.

Chromosome Mutations Cri-du-chat Deletion of material on 5th chromosome Characterized by the cat-like cry made by cri-du-chat babies Varied levels of metal handicaps

Sex Chromosome Abnormalities Klinefelter’s Syndrome XXY, XXYY, XXXY Male Sterility Small testicles Breast enlargement

Sex Chromosome Abnormalities XYY Syndrome Normal male traits Often tall and thin Associated with antisocial and behavioral problems

Sex Chromosome Mutations Turner’s Syndrome X Female sex organs don't mature at adolescence sterility short stature

Sex Chromosome Mutations XXX Trisomy X Female Little or no visible differences tall stature learning disabilities limited fertility

Some mutations even make it on SNL!