Post on 23-Feb-2016
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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