mende - Mendel’s Laws of Heredity Mendel’s Laws of...

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Unformatted text preview: Mendel’s Laws of Heredity Mendel’s Laws of Heredity Why we look the way we look... What is heredity? What is aThe passing on of characteristics (traits) from parents to offspring aGenetics is the study of heredity Mendel used peas... Mendel used peas... aThey reproduce sexually aThey have two distinct, male and female, sex cells called gametes aTheir traits are easy to isolate Mendel crossed them Mendel aFertilization ­ the uniting of male and female gametes aCross ­ combining gametes from parents with different traits Questions Questions a What did Mendel cross? a What are traits? a What are gametes? a What is fertilization? a What is heredity? a What is genetics? What Did Mendel Find? What Did Mendel Find? aHe discovered different laws and rules that explain factors affecting heredity. Rule of Unit Factors Rule of Unit Factors aEach organism has two alleles for each trait –Alleles ­ different forms of the same gene –Genes ­ located on chromosomes, they control how an organism develops Rule of Dominance Rule of Dominance aThe trait that is observed in the offspring is the dominant trait (uppercase) aThe trait that disappears in the offspring is the recessive trait (lowercase) Law of Segregation Law of Segregation aThe two alleles for a trait must separate when gametes are formed aA parent randomly passes only one allele for each trait to each offspring Law of Independent Law of Independent Assortment aThe genes for different traits are inherited independently of each other. Questions... Questions... aHow many alleles are there for each trait? aWhat is an allele? aHow many alleles does a parent pass on to each offspring for each trait Questions... Questions... aWhat do we call the trait that is observed? aWhat case (upper or lower) is it written in? aWhat about the one that disappears? aWhat case is it written in? Phenotype & Genotype Phenotype & Genotype a Phenotype ­ the way an organism looks – red hair or brown hair a genotype ­ the gene combination of an organism – AA or Aa or aa Heterozygous & Homozygous Heterozygous & Homozygous a Heterozygous ­ if the two alleles for a trait are different (Aa) a Homozygous ­ if the two alleles for a trait are the same (AA or aa) Dihybrid vs Monohybrid Dihybrid vs Monohybrid aDihybrid Cross ­ crossing parents who differ in two traits (AAEE with aaee) aMonohybrid Cross ­ crossing parents who differ in only one trait (AA with aa) Questions... Questions... aWhat is the phenotype? aWhat is the genotype? aWhat is homozygous? aWhat is heterozygous? aWhat is monohybrid crossing? ...
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