120+Genetics+and+Sex+Determination-3

120+Genetics+and+Sex+Determination-3 -...

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Click to edit Master subtitle style Genetics and inheritance; sex  determination mechanisms 
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Some Definitions § A trait is any characteristic of an individual. Heredity is the transmission of traits from parents to their offspring. n Hereditary determinants for a trait are now called genes . Alleles are different versions of a gene. The alleles in an individual are called its genotype . n Segregation : alleles segregate into different gametes during egg and sperm formation, then come back together when an egg is fertilized by a sperm to form a zygote.
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Some Definitions, contd. § Individuals with two copies of the same allele ( AA or aa ) are homozygous , and those with different copies ( Aa ) are heterozygous . § When one allele is always expressed ( A ) in the presence of the other ( a ), it is considered the dominant allele. The other is called the recessive allele. n Alleles of a gene are not always clearly dominant or recessive. In some cases, incomplete dominance occurs, and the heterozygotes have an intermediate phenotype.
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Note: n Dominance relationships have nothing to do with fitness—the ability of an individual to produce offspring in a particular environment.
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This note was uploaded on 02/17/2011 for the course BIOLOGY 120 taught by Professor Fink during the Winter '11 term at University of Michigan.

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120+Genetics+and+Sex+Determination-3 -...

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