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Test Cross for dihybrids

This resource provides insights into dihybrid crosses, similar to monohybrid crosses, and explains their role in determining an individual's genotype through homozygous and heterozygous assessments. It explores genetic variation, the meaning of 9:3:3:1 ratios, and the significance of crossing over. Additionally, it outlines the causes of mutations, differentiating between somatic and gametic mutations and their effects. The document covers essential genetic concepts, including meiosis, mutation types, and evolutionary implications, crucial for Year 12 Biology students.

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Test Cross for dihybrids

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  1. 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!!!

  2. MUTATIONS MAH - YEAR 12 BIOLOGY

  3. 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

  4. 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)

  5. What is a mutation?

  6. 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

  7. What causes Mutations?

  8. 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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  10. 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

  11. 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

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