GENETICS Gregor Mendel Genetics is the study of

GENETICS

Gregor Mendel • Genetics is the study of heredity. • Gregor Mendel (1860’s) discovered the fundamental principles of genetics by breeding garden peas.

Mendel crosspollinated pea plants • He cut away the male parts of one flower, then dusted it with pollen from another

What did Mendel conclude? • He concluded that factors are passed from one generation to the next.

eye color locus b = blue eyes eye color locus B = brown eyes The Principle of Dominance – some alleles are dominant and other are recessive. Paternal Maternal • Alleles 1. Alternative forms of genes. 2. Units that determine heritable traits.

Dominant and Recessive alleles Dominant alleles – upper-case a. homozygous dominant (BB – Brown eyes) Recessive alleles – lower case a. homozygous recessive (bb – blue eyes) b. Heterozygous (Bb – Brown eyes)

Phenotype vs. Genotype • Arrangement of genes • Outward appearance that produces the • Physical characteristics phenotype • Example: • Examples: 1. TT, Tt 1. Brown eyes 2. blue 2. tt eyes

Segregation Alleles separate during meiosis

Recessive traits show up about 1/4 th of the time. • Because there is only a 25% chance that two recessive alleles will be paired together.

Punnett square • A Punnett square is used to show the possible combinations of gametes. • Monohybrid Cross

Monohybrid Cross • Example: Cross between two heterozygotes for brown eyes (Bb) BB = brown eyes Bb = brown eyes bb = blue eyes B b B Bb x Bb b female gametes

Monohybrid Cross B b B BB Bb bb Bb x Bb 1/4 = BB - brown eyed 1/2 = Bb - brown eyed 1/4 = bb - blue eyed 1: 2: 1 genotype 3: 1 phenotype

Dihybrid Cross

Dihybrid Cross RY RY Ry r. Y ry

Dihybrid Cross RY Ry RY RRYy Ry RRYy RRyy r. Y Rr. Yy ry Rr. Yy Round/Yellow: 9 Round/green: 3 Rryy wrinkled/Yellow: 3 r. Y Rr. Yy rr. YY rr. Yy wrinkled/green: ry Rryy rr. Yy rryy 9: 3: 3: 1 phenotypic ratio Rr. Yy 1

Dihybrid Cross • Example: cross between round and yellow heterozygous pea seeds. R r Y y = round = wrinkled = yellow = green Rr. Yy x Rr. Yy RY Ry r. Y ry x RY Ry r. Y ry possible gametes produced

This means all gametes will be different! Independent Assortment • Chromosomes separate independently of eachother Bb B Ff B B F b f sperm B Bb Bb Ff B Bb diploid (2 n) f b b Ff B meiosis II b F haploid (n)

Independent Assortment • Genes for different traits can segretate independently during the formation of gametes without influencing eachother • Question: How many gametes will be produced following allele arrangements? • Remember: 1. 2. 3. 2 n (n = # of heterozygotes) Rr. Yy Aa. Bb. CCDd Mm. Nn. Oo. PPQQRrss. Tt. Qq for the

Answer: 1. Rr. Yy: 2 n = 22 = 4 gametes RY Ry r. Y ry 2. Aa. Bb. CCDd: 2 n = 23 = 8 gametes ABCD ABCd Ab. CD Ab. Cd a. BCD a. BCd ab. CD 3. Mm. Nn. Oo. PPQQRrss. Tt. Qq: 2 n = 26 = 64 gametes

Incomplete Dominance • One allele is not completely dominant over another R R r Rr Rr produces the F 1 generation r Rr Rr All Rr = pink (heterozygous pink)

Codominance • Both alleles are expressed • Example: blood 1. type A = IAIA or IAi 2. type B = IBIB or IBi 3. type AB = IAIB 4. type O = ii Black cow + white cow = spotted cow

Which shows more genetic variation. (more combos? ) • Male CC with female Cc C • Male cc with female Cc C C c c c

Genetic Engineering

Gene Therapy

Is cloning a possibility? • Is it right to use cloning to create an entirely new human being? • Is it ethical to create an embryonic copy of John Doe to supply cells to keep John alive? • Does a multicellular ball of tissue -- an embryo -- have the same rights and status as a human being?

How does Mendel’s principles apply to organisms • The basic principals can be applied to humans as well as any other living organism.

And now it’s time for…. • Spongebob Genetics!!!!!