Genetic Changes

Genetic ChangesGene and Chromosomal Mutations

Mutations Mutations are a result in a change in DNA

sequence › A protein with a different AA sequence could be

produced.› Germ Cell - If mutations occur in sex cells they may

be passed on to the next generation.› Somatic- A mutation occurring only in body cells may

be a problem for the individual but will not be passed on to the offspring.

Mutations may be classified as chromosomal alterations or gene mutations

› Chromosomal alterations are generally more severe because many genes are usually involved.

Significance of Mutations• Most are neutral

• Eye color• Birth marks

• Some are harmful• Cystic Fibrosis• 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 damageMistakes when DNA is copied

Types of Gene Mutations

Silent mutation› any mutation that is not expressed

because it does not cause a change in amino acid chain.

Point mutation › base-pair substitution› 1 base is replaced by a different

base

• Point mutation• Only one nucleotide

changes, but it makes a different protein

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 ATE THE RAT THE FAT CAT XLW ATE THE

RAT– Deletion

THE FAT CAT ATE THE RAT THE FAT ATE THE RAT

• Frameshift • Causes every codon in the DNA sequence to

be changed after the mutation:• Insertion- one or more bases are added• Deletion- one or more bases are removed

A

Chromosomal Alterations

Deletion - part of chromosome is left out. Duplication - part of chromatid breaks

off add attaches to the sister chromatid creating a duplication of genes on the same chromosome.

› Deletion and duplication mutations are errors that occur during crossing over in Meiosis I.

Translocation - when part of one chromosome breaks off and is added to a different chromosome.

Inversion - when part of a chromosome breaks off and is reinserted backwards.

Structural Errors

Chromosome MutationsChanges in number and structure of

entire chromosomes Original Chromosome ABC * DEFDeletion AC * DEFDuplication ABBC * DEFTransposition ACB * DEFInversion AED * CBFTranslocation ABC * JKL

GHI * DEF

A dinky Y chromosome and the hairy ear gene on the Y chromosome

Chromosomal Deletion