(9-18-06) Theories of Inheritance Contd..

(9-18-06) Theories of Inheritance Contd.. - X R r o R RR Rr...

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Theories of Inheritance Continued Mendel’s Selection of Plants - selection of pea plants o constant differentiating characteristics o protect the plants from foreign pollen o arrange them in generations o statistical analysis on the outcomes Round Peas X Wrinkled Peas - What was the outcome o All rounds peas What was Mendel Seeing? - phenotype o outward appearance o not necessarily reflective of the genetic code - genotype o genetic code o some genes are ‘hidden’ because they are recessive Dominant vs. Recessive - dominant traits are always exhibited if they’ve been inherited - recessive traits are exhibited only if 2 are inherited - dominants characteristics are assigned a capital letter- R=Round - recessive characteristics are assigned a lower case letter- r=round Round Peas vs. Wrinkled Peas - X R R - r Rr Rr - r Rr Rr - alleles- different forms of genes - genes- code for characteristics - homozygous dominant- DD - homozygous recessive- dd - heterozygous- Dd Second Generation Round Peas X Round - what was the outcome? o 3 round to 1 wrinkled o
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Unformatted text preview: X R r o R RR Rr o r Rr rr Mendel’s Law of Segregation-the separation of alleles during reproduction of sex cells, allowing maintenance of their separate identities and later full expression of their traits Mendel’s Law of Independent Assortment-The inheritance of characteristics in one offspring does not influence the inherited characteristics in subsequent offspring Dominant Traits-Achondroplasia Dwarfism o Caused by one change in one chemical base o 1 in 100,000 live births o Average sized body trunk o Shortened limbs o 80% born to average sized parents o Once inherited it can be passed on Dwarf X Average Stature- X D d- d Dd dd- d Dd dd Dwarf X Dwarf- X D d- D DD Dd- d Dd dd Recessive Traits-albinism-1 in 37,700 births-no melanin produced in skin, hair, or iris-found throughout the world-high incidence of skin cancer Heterozygous Parents- X A a- A AA Aa- a Aa aa- 25% homozygous dominant- 50% heterozygous- 25% homozygous recessive...
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(9-18-06) Theories of Inheritance Contd.. - X R r o R RR Rr...

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