Genes&Society_1 Colour slide perpage_Lecture2

It can pertain to one or more than one genes a

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Unformatted text preview: constitution or genetic make-up of a cell, an individual makeorganism. It can pertain to one or more than one gene(s). A homozygous genotype has the same alleles; heterozygous genotype has different alleles genotype has the same alleles; a heterozygous genotype has different alleles ] GG homozygous Gy yG heterozygous yy homozygous There are only two phenotypes: green or yellow phenotypes: [Phenotype: The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences. ] 10 Mendel’s Mendel’s three laws of heredity: 1. Law of segregation: Genetic traits are control by paired unit factors (later known as genes) which one form (allele) of each paired unit factors is segregated into the sex cell (e.g. allele for red OR green colour of the seed) 2. Law of dominance: Law One form of the gene (allele) will always be dominant. 3. Law of Independent assortment: Different traits are inherited independently from each other (e.g. can be tall and green or tall and red) Note: Mendel’s laws are not always true in nature. 11 Dominance Dominance & Recessiveness Incomplete/Partial Dominance Dominance & Codominance 12 Dominant Trait and Allele Dominant Trait and Allele Dominant trait refers to a genetic feature that hides the recessive trait in the phenotype of an individual. A dominant allele causes the phenotype to be seen in a heterozygous (Aa) (Aa) genotype. For example, if a person has one allele for blue eyes and one for brown, that person will always have brown eyes because they are the dominant have brown eyes because they are the dominant trait. trait. For a person to have blue eyes, both their alleles must be blue (recessive). When a person has two dominant alleles they are referred to as has two dominant alleles, they are referred to as homozygous homozygous dominant. If they have one dominant allele and one recessive allele, they are referred to as heterozygous as heterozygous. 13 Is Is this possible? Dr X Dr Sperm D Egg r DD rD Dr rr D r 14 Recessive Trait and Allele Recessive Trait and Allele The term "recessive allele" refers to an allele that causes phenotype (visible or detectable causes a phenotype (visible or detectable characteristic) characteristic) that is only seen in homozygous genotype (an organism that has two copies of the same allele; recessive trait) and never in hete...
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This note was uploaded on 03/21/2013 for the course GEK 1527 taught by Professor Tan during the Winter '11 term at National University of Singapore.

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