GENETICS Why do you look like that?!?

A little background… Gregor Mendel- “Father of Genetics” –Austrian monk and biologist in the mid-1800s –Used pea plants to figure out how traits were inherited (passed down)

Vocabulary Genetics: the study of heredity, or how genes are inherited

Allele: variation of a trait; form of a gene ex. Trait- pod color / Alleles- yellow, green

Dominant: allele that can mask the other (uppercase letters- A) Recessive: allele that can be masked by the other (lowercase letters- a)

Homozygous: both alleles in the pair are the same (AA or aa) Heterozygous: both alleles in the pair are different (Aa)

Genotype: genetic make-up (the genes) of an organism Ex. Uu or UU Phenotype: physical appearance expressed by the genes Ex. Unibrow

G – green pea pods g – yellow pea pods (Dominant) (Recessive) Genotypes  GG Gg gg Terms  Phenotypes  Homozygous dominant Homozygous recessive Heterozygous Green pea pods Green pea pods Yellow pea pods

Mendel’s Work

Laws of Heredity Law of Segregation: Two alleles for a trait separate during gamete formation

Laws of Heredity Law of Independent Assortment: –Alleles from different genes separate independently of one another during gamete formation

Punnett Squares Used to figure out the possible genotypes and phenotypes (ratios) Monohybrid cross: one trait of an individual is crossed with the same trait of another individual

Monohybrid Cross Example Let’s look at pea pod color: –Green is dominant (G) and yellow is recessive (g) –Example: Homozygous dominant (GG) crossed with homozygous recessive (gg) GG g g Genotype ratio 4 Gg: 0 GG: 0 gg 100% Gg Phenotype ratio 4 green: 0 yellow 100% green Gg

Punnett Squares Dihybrid cross: two traits of an individual are crossed with the same two traits of another individual

Dihybrid Cross Example Must find all possible allele combinations: Traits - seed shape and seed color Alleles: R = Round r = Wrinkled Y = Yellow y = green Female: RrYy Male: RrYy both are round and yellow All combinations for each: Female: RY, Ry, rY, ryMale: RY, Ry, rY, ry

Dihybrid Cross Example Cross these combinations to find possible genotypes/phenotypes of offspring: RY RyrYry Ry rY ry RRYY RRYy RrYY RrYy RRYy RRyy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy

Dihybrid Cross Example Cross these combinations to find possible genotypes/phenotypes of offspring: Genotype ratio: RRYY1/16 RRYy 2/16 RrYY 2/16 RrYy 4/16 Rryy 1/16 Rryy 2/16 rrYY 1/16 rrYy 2/16 rryy 1/16 Round and Yellow 9/16 Round and Green 3/16 Wrinkled and Yellow 3/16 Wrinkled and Green 1/16 Phenotype ratio:

Types of Dominance: 1) Complete Dominance- One allele can completely mask another RR- Red Rr- Red rr- white

Types of Dominance Incomplete Dominance: one allele is partially covered by another RR- REDRR’- PINK R’R’- WHITE

Types of Dominance Co-dominance: Both alleles are dominant, so they both show through RR- RED RW- Red & WhiteWW- White

Types of Dominance 4) Multiple Alleles- when a trait has more than two alleles Ex. Blood Type –I A - Type A –I B - Type B –i- Type O Both complete and co-dominance are shown in creating phenotypes Type A- I A I A, I A i Type B- I B I B, I B i Type AB- I A I B Type O- ii

Types of Dominance 5) Sex-linked- Allele for trait is found on a sex chromosome Ex. Hemophilia –Normal- X H –Hemophilia- X h –Nothing at all- Y

Law of Segregation Image (Google Image search): s/pics/lawofsegregation.gif s/pics/lawofsegregation.gif Law of Independent Assortment Image (Google Image search): The Genetic Work of Gregor Mendel. Ancient Lights Discovery Education. 24 January 2010