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 are SEPARATED when gametes are formed and recombine during fertilization

3. Law of Independent Assortment Genes for different traits are inherited independently of each other because 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?

Show a dihybrid cross between two complete heterozygotes S= yellow s= green Y= round y= wrinkled Show a dihybrid cross between two complete heterozygotes How many round yellow? How many round green? How many wrinkled yellow? How many wrinkled green?

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

What’s on our agenda? Monday: Welcome back! Brief Genetics Review Learn Blood Types & Blood type punnetts Tuesday: Learn Pedigrees Wednesday: Receive Genetics Test Study Guide Material= Mendel’s laws, Punnetts, Dihybrids, Ratios, Codomiance, Incomplete Dominance, Sex-linked Inheritance, Blood types, Pedigrees Thurs: Take Genetics Unit Test Friday: Receive FULL YEAR study guide in preparation for MCAS (June 1 & 2). Due 5/31 (D & E, due 5/27 F Block Left to cover: Ecology, Evolution

Non-Mendelian Genetics: Exceptions to Complete Dominance

Incomplete Dominance - Blend Heterozygous genotype= blend of two phenotypes RR= Red RW= pink WW= white (For many genes, such as the two mentioned above, the dominant allele codes for the presence of some characteristic (like, “B” codes for “make brown pigment” in someone’s eyes), and the recessive allele codes for something along the lines of, “I don’t know how to make that,” (like “b” codes for the absence of brown pigment in someone’s eyes, so by “default,” the eyes turn out blue). If someone is a heterozygote (Bb), that person has one set of instructions for “make brown” and one set of instructions for, “I don’t know how to make brown,” with the result that the person ends up with brown eyes. There are, however, some genes where both alleles code for “something.” One classic example is that in many flowering plants such as roses, snapdragons, and hibiscus, there is a gene for flower color with two alleles: red and white. However, in that case, white is not merely the absence of red, but that allele actually codes for, “make white pigment.” Thus the flowers on a plant that is heterozygous have two sets of instructions: “make red,” and “make white,” with the result that the flowers turn out mid-way in between; they’re pink.)

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? 4:51 https://www.youtube.com/watch?v=Y1PCwxUDTl8 TRY ANOTHER!Calico Cat Colors B: Black Y: Yellow NOTES: Horse Fur Color R= Brown W= White

Sex-Linked

Sex-Linked 4:51 https://www.youtube.com/watch?v=Y1PCwxUDTl8

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

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 DIDN”T DO WITH D

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 https://www.youtube.com/watch?v=KXTF7WehgM8 0:45

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 https://www.youtube.com/watch?v=KXTF7WehgM8 Specific protein surface on RED BLOOD SURFACE antibodies for every shape in immune system except your own blood: DO NOT WANT TO ATTACK OUR OWN CELLS Universal Donor (can give to everyone): 0 Blood…. why? Universal Recipient (can accept from anyone): AB Blood…..why?