genetic mutations
DESCRIPTION
GENETIC MUTATIONS. Sexual Reproduction. Results in variations Variations help organisms adapt Allow breeders to develop new strains of plants/animals Most variations come from segregation and crossing over in meiosis. Source of Variations. Most variations come from: Segregation - PowerPoint PPT PresentationTRANSCRIPT
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GEN
ETIC MU
TATION
S
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Sexual Reproduction
• Results in variations • Variations help
organisms adapt – Allow breeders to
develop new strains of plants/animals
• Most variations come from segregation and crossing over in meiosis
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Source of Variations• Most variations come from:– Segregation– Crossing over
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Mutations
• Mutations are sudden changes in the structure or amount of genetic material
• Most mutations are harmful; some are beneficial (i.e. ones that allow species to meet needs of environment)
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Types of Mutations
• 2 Main Types:– Chromosome Mutation = changes
structure of all/part of chromosome– Gene Mutation = affects a gene on
a chromosome• Mutation must be in DNA of sex
cells in order for it to be passed on.
• Mutations in body cells can’t be passed on.
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What Causes Mutations
• Random error in DNA replication
• Environmental Factors (called mutagens)– Radiation (X-rays)– UV light– Chemicals (chloroform
and mustard gas)
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Chromosome Mutations
1) Translocation• One part of a chromosome is transferred to a
non-homologous chromosome
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Chromosome Mutations
2) Inversion• One part of a chromosome is rotated (reverses
order of genes)
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Chromosome Mutations
3) Addition• One part of a
chromosome breaks off and attaches to a homologous chromosome
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Chromosome Mutations
4) Deletion• One part of a chromosome breaks off. This
results in a loss of some genes• E.g. Angleman’s Syndrome (Chromsome #15)
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Chromosome Mutations5) Non-disjunction• Addition or loss of a whole chromosome (ones
that usually separate during meiosis remain together)
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Chromosome Mutations
6) Polyploidy• More than normal copy of chromosomes
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Gene Mutations
• Genes tell the cell what order to arrange amino acids (to form proteins)
• Changes in the DNA sequence will change the message transcribed into mRNA & likely change the protein
• Types of Mutations:– Point Mutation– Base Substitution
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Point Mutation
• Single nucleotide in a gene is changed• This is drastic as all triple codons beyond are
changed• This makes the gene useless and the organism
will lack the protein normally made by the gene
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Base Substitution
• One base in a nucleotide is substituted for another.
• This changes 1 codon and one amino acid• Results in a protein that doesn’t function
normally• E.g. PKU– Substitution of GT to AT