Question??? If two blue eyed people have kids, what color eyes will their kids have? If two brown eyed people have kids, what color eyes will their kids have? Have color sticks!

Genetics: Episode I A Monk, His Peas, and Genes Ag Biology Sutherlin AST

Genetics What is genetics? What is heredity? What are traits? Branch of biology studying heredity What is heredity? Passing of traits from parent to offspring What are traits? Physical characteristics

Genetics Gregor Mendel A monk, 1800’s Austria First to study and determine factors of heredity Used carefully controlled experiments: only changed one factor at a time

Genetics Why peas? Produce sexually Male and female parts on same flower Male parts are called? Female parts are called?

Genetics Pollination – male sex cells (pollen) lands on female parts (pistil) Fertilization – DNA from pollen combines with DNA from ovum (egg) Becomes seed

Genetics Self-pollination: male and female sex cells come from same plant Cross-pollination: sex cells come from two different plants Create hybrid

Genetics What did Mendel do? Studied TALL traits and SHORT traits in plants (parents = P1) Cross-pollinated these plants to get hybrids ALL of the offspring (F1) were TALL

Genetics What did Mendel do next? Took the offspring (F1), then crossed them together This time, not all offspring the same.

Genetics What did Mendel do next? ¾ of plants were tall ¼ were short plants This is called a 3:1 ratio

Genetics So what does this mean? Unit Factors Mendel concluded two factors control each trait We know these are genes One factor from the mother One from the father

Genetics Unit Factors For each gene, there are alleles Different forms of each gene Example: there is a gene for height (T) It could be the Tall allele – T It could be the Short allele - t

Genetics Unit Factors Since we have two copies of each gene, three combinations Two Tall (TT) alleles Two Short (tt) alleles One Tall allele and one short allele (Tt) But how is this possible?

What else does this mean? Genetics What else does this mean? Rule of Dominance Only one allele is observable Dominant alleles: observable trait Recessive alleles: unobservable trait So which is dominant for height in pea plants?

Genetics So what does each look like? TT: tt: Tt:

Genetics What about cows? If you cross purebred black angus cattle with red angus cattle, you get black cattle What does this mean?

Question: You are growing peas. Use the chart of dominant and recessive genes. You are crossing axial (AA) and terminal (aa) bud plants. What would the F1 generation be? Would terminal or axial be more beneficial for the plant?

Mendel’s 7 Traits of Pea Plants

Genetics Two organisms can look the same, but carrying different genes Phenotype: how an organism looks (think physical) Tall? Short? Genotype: the genes an organism has Tall: could be Tt Tall: could be TT

Genetics Homozygous – both alleles are the same TT, tt Heterozygous – alleles are different Tt All of this, by a monk, in the 1800s!

Genetics Dihybrid cross Looking at just one trait (height) is monohybrid (one) But what if we track more than one trait?

Round Yellow X Wrinkled Green Genetics Mendel’s Dihybrid Cross Round peas (R=round, r=wrinkled) Seed color (Y=yellow, y=green) Parents (P1) Round Yellow X Wrinkled Green

Genetics Mendel’s Dihybrid Cross Parents (P1) Round Yellow X Wrinkled Green RRYY rryy Result? Offspring (F1) ALL Round Yellows RrYy

Genetics Mendel’s Dihybrid Cross F1 Cross X So now what do you get?

Genetics Mendel’s Dihybrid Cross The point? Law of Independent Assortment: genes for different traits are inherited independently of one another (green seeds do not have to be wrinkled!)

Genetics Punnett Squares Tool for projecting Phenotypes and Genotypes of offspring Developed by Reginald Punnett (England)

Genetics Monohybrid Punnett Square

Genetics Dihybrid Punnett Square