mutations
DESCRIPTION
MUTATIONS. MUTATIONS. ANY change in the DNA sequence that affects genetic information Changes may be good or bad There may or may not be a visible effect in an organism or its offspring…. So...when are mutations inherited?. - PowerPoint PPT PresentationTRANSCRIPT
MUTATIONS• ANY change in the DNA
sequence that affects genetic information
• Changes may be good or bad• There may or may not be a
visible effect in an organism or its offspring…
So...when are mutations inherited?• Mutations will only be
passed on to offspring if they occur in the gamete (sex cells)
When are mutations inherited?
• Mutations that occur in regular body cells (somatic cells) will be lost when the cell dies• Mutation in lung cell will lead to cancer, but cancer isn’t passed on to offspring
When are mutations inherited?
• Lethal mutations result in the death of the organism• Often miscarriage
Mutagens may cause changes• X-rays• Ultraviolet rays• Microwaves• Cosmic radiation• Chemicals:
• Benzene• Asbestos
•Formaldehyde•Toxic industrial chemicals
Two Types1. GENE MUTATIONS—
• changes in a single gene
2. CHROMOSOMAL MUTATIONS—• changes in whole chromosomes
(chromosome number or chromosome itself)
1. GENE MUTATIONS
a. POINT MUTATION (Substitution)
• Single nucleotide is substituted for the wrong one
• Ex: A-G instead of A-T
• This can lead to…
1. GENE MUTATIONS
1) Silent mutation: has NO effect since some amino acids have multiple sequences
Ex: CUC codes for leucine
CUA also codes for leucine
1. GENE MUTATIONS
2) Missense mutation: causes the wrong amino acid to be in sequence
Ex: CUU codes for leucine
CCU codes for proline
1. GENE MUTATIONS
3) Nonsense mutation: causes an early STOP codon
Ex: UCA codes for serine
UGA codes for STOP
1. GENE MUTATIONS
b. FRAMESHIFT MUTATION
• insertion or deletion of one or more nucleotides
• All codons are shifted
• May cause serious effects
• Such mutations can alter a protein so that it is unable to perform its normal functions.
2. CHROMOSOMAL MUTATIONS
b. DUPLICATION
• Opposite of deletion
• A segment of the chromosome is repeated
2. CHROMOSOMAL MUTATIONS
c. INVERSION
• Direction of genes is reversed within chromosome (part is upside-down)
2. CHROMOSOMAL MUTATIONS
d. TRANSLOCATION
• When part of a chromosome breaks off and relocates to another part
NONDISJUNCTION
• MONOSOMY•Having only ONE copy of a chromosome instead of TWO
•EX: Turner’s syndrome (has only one X chromosome)
NONDISJUNCTION
• TRISOMY•Having THREE copies of a chromosome instead of TWO
•EX: Down Syndrome (3 copies of chromosome #21, trisomy 21)
Somatic Cells (Body Cells)
• During or before mitosis
• All new cells will also be altered
• The change is permanent
• Only effects organism, not offspring