Mendels Laws of Heredity Why we look the

Mendel’s Laws of Heredity Why we look the way we look. . .

Mendel used peas. . . They reproduce sexually They have two distinct, male and female, sex cells called gametes Their traits are easy to isolate

Mendel crossed them Fertilization - the uniting of male and female gametes Cross - combining gametes from parents with different traits

What Did Mendel Find? He discovered different laws and rules that explain factors affecting heredity.

1. Rule of Dominance The trait that is observed in the offspring is the dominant trait (uppercase) The trait that is masked in the offspring is the recessive trait (lowercase)

2. Law of Segregation Genes appear in pairs on homologous chromosomes SEPARATED when gametes are formed Recombine during fertilization

3. Law of Independent Assortment The genes for different traits are inherited independently of each other. Homologous chromosomes move randomly to gametes Explains why siblings look different

Genetics Continued Dihybrid crosses Exceptions to Mendelian Genetics ◦ Incomplete vs. Complete Dominance ◦ Codominance ◦ Sex-Linked Genetics ◦ Blood Types (Multiple Alleles)

Monohybrid Vs Dihybrid Monohybrid Cross crossing parents who differ in only one trait (AA with aa) Dihybrid Cross - crossing parents who differ in two traits (AAEE with aaee)

S= yellow s= green Y= round y= wrinkled How many round yellow? How many round green? How many wrinkled yellow? How many wrinkled green?

Dihybrid Cross - 2 traits

Bozeman Tutorial http: //www. youtube. com/watch? v=Y 1 PCwx. UDTl 8

Incomplete Dominance Blend Heterozygous genotype= blend of two phenotypes RR= Red RW= pink WW= white

Codominance – Both show Both alleles of the trait show in the heterozygote

Codominance: Both traits show in heterozygotes Try these: what are the phenotype ratios? Cows R= Brown W= white Calico Cat Coats B: Black Y: Yellow

Sex-Linked

Sex-Linked

Sex-linked Punnett C= color-blindness XX= Female XY= Male Is mom colorblind? Is dad colorblind? What is the chance that they have: 1) 2) 3) 4) a colorblind girl? a female carrier? an unaffected male? an affected male?

Polygenic: controlled by many genes Polygenic inheritance is a fancy term for those genetic traits that are controlled by more than 1 gene - Height, Skin Color Because there are MANY genes that influence polygenic inheritance, you see a spectrum of phenotypes

Blood Types: Multiple Alleles - What is multiple allele inheritance? - Non-Mendelian Inheritance Pattern - involves more than just 2 alleles - that means there is more than two phenotypes

Blood Types: Multiple Alleles - Example: Blood Type (Red Blood Cells) - There are markers on the surface of RBCs - Our immune system has antibodies: ATTACK foreign invaders (germs, viruses) - YOU DO NOT WANT ANTIBODY for your BLOOD TYPE - What would be the result? Your immune system attacks your body!!

Multiple Alleles - Blood Type Universal Donor (can give to everyone): 0 Blood…. why? Universal Recipient (can accept from anyone): AB Blood…. . why?