by123 chapter 14 - Chapter 14: Mendel and the Gene Idea...

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Chapter 14: Mendel and the Gene Idea Gregor Mendel is the father of genetics Allele - different form of the gene Locus - the place where the gene is on a chromosome Dominant genes do not always outnumber recessive genes Genotype - what the genes are; PP, Pp, pp Phenotype - how the genes are expressed; purple, purple, white Heterozygote - Pp Homozygote - PP, pp True - breeding - breeding between two of the same homozygotes Monohybrid - heterozygous for one character Dihybrid - heterozygous for two characters MENDEL’S FIRST LAW – THE LAW OF SEGREGATION o The factors separate when the gametes are formed and only one factor is present in each gamete (diploid haploid) o Monohybrid cross - Pp x Pp P p P PP Pp p Pp pp Genotype ratio- 1:2:1 Phenotype ratio- 3:1 P- purple p- white PP,pp- homozygous Pp- heterozygous Recessive phenotype=homozygous genotype A cross an find the dominant phenotypes genotype by crossing it with a recessive phenotype (always homozygous recessive) In a somatic cell, for every gene, there are two alleles, sometimes more.
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MENDEL’S SECOND LAW- THE LAW OF INDEPENDENT ASSORTMENT o Holds only when genes are not linked
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This note was uploaded on 08/07/2009 for the course BY 123 taught by Professor Cusic during the Spring '07 term at University of Alabama at Birmingham.

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by123 chapter 14 - Chapter 14: Mendel and the Gene Idea...

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