Learning Objectives I will be able to: Describe the work of Gregor Mendel Distinguish between dominant and recessive traits Describe the law of segregation and law of independent assortment

Learning Objectives I will be able to: Distinguish between genotype and phenotype Identify homozygous and heterozygous alleles Use a Punnett square to predict the results of monohybrid and dihybrid crosses Explain how a testcross shows the genotype of an individual whose phenotype expresses the dominant trait

Gregor Mendel (1822-1884) Considered the “father of genetics” Studied traits in pea plants

Gregor Mendel (1822-1884) Character – heritable feature; like flower color

Gregor Mendel (1822-1884) Traits – variant of a character; like purple/white flowers

Gregor Mendel (1822-1884)

Gregor Mendel (1822-1884) P generation – parent generation

Gregor Mendel (1822-1884) F1 generation – offspring of the P generation

Gregor Mendel (1822-1884) F2 generation – offspring of F1 generation Gene – region of DNA that codes for a particular protein

Alleles Alleles – various forms of a gene (letters) Typically a dominant allele and a recessive allele

Alleles Dominant allele masks the recessive allele Dominant brown (B) masks recessive blue (b)

Genotype vs. Phenotype Genotype - Alleles present in an organism BB, Bb, bb Phenotype – physical characteristic brown eyes or blue eyes

Heterozygous vs. Homozygous Heterozygous – 2 different alleles Bb Homozygous – two of the same allele BB – brown eyes bb – blue eyes

Law of Segregation During meiosis, the hereditary factor (homologous pair of chromosomes) separate Offspring receives one allele from each parent

Law of Segregation During meiosis, the hereditary factor (homologous pair of chromosomes) separate Offspring receives one copy from each parent

Law of Independent Assortment Factors of different traits will be distributed independent of each other

Monohybrid Crosses Cross with only one gene Uses Punnett square

Homozygous Dominant x Homozygous Recessive Graphic organizer #1

Homozygous Dominant x Homozygous Recessive Genotype: 4Bb Phenotype: 4 brown eyes

Homozygous Dominant x Homozygous Recessive G: 4Bb P: 4 brown eyes

Homozygous Dominant x Homozygous Recessive Organizer #2 W = tall w = short Genotype: Phenotype:

You find a yellow pea plant. You know that yellow is dominant to green You find a yellow pea plant. You know that yellow is dominant to green. What is the genotype?

Test Cross Tests what alleles are present Cross a dominant phenotype with a recessive phenotype

Test Cross Tests what alleles are present Cross a dominant phenotype with a recessive phenotype

Test Cross

Dihybrid Crosses Cross between 2 different genes Color and seed skin 16 squares

Dihybrid Crosses Cross between 2 different genes Color and seed skin 16 squares

Heterozygous x Heterozygous #1 in notes RrYy x RrYy

Dihybrid Cross RrYy x RrYy R = round r = wrinkled Y = yellow y = green RY Ry rY ry RY Ry rY ry

Dihybrid Cross Round/Yellow: Round/green: wrinkled/Yellow: wrinkled/green: Phenotypic ratio: RY Ry rY ry RY Ry rY ry

Dihybrid Cross RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio

Dihybrid Cross #2 in notes Parent A: heterozygous for both traits Parent B: Heterozygous for height Homozygous recessive for eye color If height is represented by H and eye color is represented by B, what will the cross look like?

Dihybrid Cross Organizer #9 HhBb x Hhbb H = tall h = short B = brown eyes b = blue eyes

Dihybrid Cross HhBb x Hhbb HB, Hb, hB, hb Hb, Hb, hb, hb

Dihybrid Cross HB Hb hB hb Hb Hb hb hb

Dihybrid Cross HB Hb hB hb Hb Hb hb hb HHBb HHbb HhBb Hhbb

Dihybrid Cross Phenotype? Tall/brown eyes: Tall/blue eyes: Short/brown eyes: Short/blue eyes:

Dihybrid Cross Phenotype? Tall/brown eyes: 6 Tall/blue eyes: 6 Short/brown eyes: 2 Short/blue eyes: 2

Incomplete Dominance Dominant trait is not completely expressed over recessive trait Heterozygous forms “hybrid” snapdragons

Incomplete Dominance

Pink flowers (Rr) x pink flowers (Rr)

Incomplete Dominance Genotype: 1RR:2Rr:1rr Phenotype: 1 red:2 pink:1 white

Pink flowers x pink flowers Genotype: 1RR:2Rr:1rr Phenotype: 1 red:2 pink:1 white

Pink flowers x Red flowers R R R r

Pink flowers x red flowers R R G: 2RR:2Rr P: 2red:2pink: R RR RR r Rr Rr

Codominance 2 alleles are expressed at the same time 2 alleles are dominant

Codominance B B Black x white chicken W

Codominance B B Black x white chicken G: 4BW P: 4 speckled W BW BW

Codominance Now cross 2 speckled chickens BW x BW

Codominance B W G: 1BB:2BW:1WW B BB BW P: 1 black, 2 speckled, 1 white W BW WW G: 1BB:2BW:1WW P: 1 black, 2 speckled, 1 white

Multiple Alleles More than 2 alleles code for a trait Blood types Which blood types do you know?

Multiple Alleles More than 2 alleles code for a trait Blood types Which blood types do you know? A, B, AB, and O are the standard types

Multiple Alleles A and B are dominant O is recessive

Multiple Alleles Mother has AB blood (IAIB) Father has B blood (IBi) IAIB x IBi

Multiple Alleles Phenotypes: 1 AB blood 1 A blood 2 B blood

Multiple Alleles Mother has IBIB blood Father has IAi blood Draw the Punnett square

Multiple Alleles IB IB IA IA IB IA IB i IB i IB i Phenotype: 2 AB 2 B

Sex Linked Traits Traits located on X or Y chromosome Much more common in males than females Why?

Sex Linked Traits Traits located on X or Y chromosome Much more common in males than females

Y linked Traits Relatively uncommon SRY gene – provides “male information”

X linked Traits Much more common Disorders like hemophilia Blood clotting disorder Common in old European royalty red-green colorblindness Much more common in males than females

Sex linked Punnett square The first step in making a sex linked Punnett square is always to write down the Xs and Ys of mom and dad!

X linked Traits Example Normal father x carrier mother Then do this as you would do a normal Punnett square

X linked Traits Phenotype 2 normal females 1 normal male 1 colorblind male Genotype 1XBXB female 1XBXb female 1XBY male 1XbY male

X linked Traits Try your luck! Mother who is carrier for hemophilia XHXh Normal father XHY

X linked Traits XH Xh XH XH XH Y XHY XhY

Sex Influenced Traits Found on autosomes, not sex chromosomes Influenced by sex Often affected by hormones baldness

Sex Influenced Traits Female Male HH Normal Normal Hh Normal Disease hh Disease Disease

Pedigree Family tree used to show traits inherited over time

Pedigree If trait is autosomal, it will appear in both sexes equally If sex-linked, it will appear in males much more often

Recessive Pedigree This pedigree codes for brown eyes (B) and blue eyes (b) Pedigree graphic organizer

Dominant Pedigree Aa Aa aa Aa A? A? aa aa Aa aa aa aa

Hemophilia Pedigree

Polygenic Traits Trait that is coded for by more than one gene Usually continuous traits in humans Height Skin color

Linkage Groups Linkage groups – genes that tend to be inherited together Genes located close together on one chromosome Avoid crossing-over.

Alterations in Chromosome Structure Deletion – pieces of a chromosome are removed

Alterations in Chromosome Structure Duplication – pieces of a chromosome are duplicated

Alterations in Chromosomes Inversion – pieces of a chromosome are inverted

Alteration in Chromosomes Translocation – part of a chromosome attaches to a non-homologous chromosome