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Test Cross for dihybrids. These work the same as monohybrid crosses To determine if an individual is homozygous or heterozygous for a trait we cross with a homozygous recessive individual!!!. MUTATIONS. MAH - YEAR 12 BIOLOGY. DO NOW. How does genetic variation arise? 9:3:3:1 means what?
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Test Cross for dihybrids • These work the same as monohybrid crosses • To determine if an individual is homozygous or heterozygous for a trait we cross with a homozygous recessive individual!!!
MUTATIONS MAH - YEAR 12 BIOLOGY
DO NOW • How does genetic variation arise? • 9:3:3:1 means what? • What does crossing over mean? • Write four ‘facts’ regarding meiosis? • Carry on with genetics handout I gave you the other day
MIND MAP • Two parts: • Genetics: Genes, alleles, chromosomes, dominance, recessive, genetic variation, meiosis, recombination, independent assortment, fertilisation, mutations, gene mutations, chromosome mutations, dihybrid crosses, F1, F2 • Evolution: variation, gene pool, evolution, natural selection ( 3 types), mate selection, genetic drift, founder effect, bottleneck, gene migration (gene flow)
What is a Mutation? .....A change in a DNA base sequence that can not be easily repaired Varying effects based on type of mutation Normal spontaneous mutation rate is about 106 to 108 replications
What causes Mutations? • MUTAGENS: are agents that causes genes to mutate • THEY INCLUDE: • High energy radiation – cosmic rays, x-rays, ultraviolet radiation, radioactive decay • Chemicals – nitrogen mustards, epoxides, nitrous acid, formaldehyde, acridine dyes and alkylating agents, Pg. 169 Bayley – summarise how radiation and chemicals effect DNA Pg 81/82 Biozone
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Effects of Mutations • Proteins • Changing biochemical pathways • Changes to chromosomes (repeats: fragile X) • Changes in cell division processes • Mutations lead to evolution, because the protein formed from a mutation may be useful producing an organism more suited to its environment
Mutations • If a mutation occurs in a somatic cell it only affects that organisms and cannot be passed on. • If the mutation occurs in a gametic cell it may be passed on to the offpspring