Genetics SPI.4.4 Determine the probability of a particular trait in an offspring based on the genotype of the parents and the particular mode of inheritance. SPI.M.2 Predict the outcome of a cross between parents of known genotype.

Genetics The study of heredity

Gregor Mendel Father of genetics Worked with pea plants Studied various traits Trait – genetically determined characteristic or condition

Different forms of the same gene Alleles Different forms of the same gene Example: Hair color

First Experiment P (parental) F1 100% Purple

Second Experiment F1 F2 75% Purple and 25% White

Gregor Mendel Four major conclusions: Inheritance factors Principle of Dominance Law of Segregation Law of Independent Assortment

Mendel’s Conclusion Inheritance is determine by factors passed down by parents *factors = genes

Mendel’s Conclusions 2. Some alleles are dominant to others Recessive *Appears in absence of dominant allele *Lower case letter Dominant *Always appears when present *Capital letter

Purple (P) color is dominant to white (p) color Genotype Allele combination Phenotype Physical appearance Trait = Flower Color Purple (P) color is dominant to white (p) color Genotype? PP or Pp pp Phenotype? Purple White

Homozygous Same alleles Heterozygous Different alleles

Mendel’s Conclusions 3. Law of Segregation A pair of alleles is separated in the formation of gametes Meiosis

Mendel’s Conclusions 4. Law of Independent Assortment Alleles on non homologous chromosomes will be distributed randomly into gametes

Punnett Squares Monohybrid 1 trait Dihybrid 2 traits 14

Punnett Square A A Aa Aa a a Aa Aa Gamete Parent 2 (aa) Parent 1 (AA) Offspring genotype a Aa Aa

Example Tt tt Tall is dominant to Short in pea plants Tall – T Short – t Cross a heterozygous tall plant with a short plant Parent 1 Parent 2 Tt tt 16

Example Cross 17

Monohybrid Cross Rules 100% of the offspring – dominant phenotype At least 1 parent is homozygous dominant 100% of the offspring – recessive phenotype Both parents are homozygous recessive 75% dom. pheno. & 25% rec. pheno. Both parents are heterozygous 50% dom. Pheno. & 50% rec. pheno. 1 parent is heterozygous & 1 parent is homozygous recessive

Autosomal Versus Sex Chromosomes Autosomes All chromosomes except X or Y Sex Chromosomes Female XX Male XY 19

Autosomal Inheritance Equal chance for each gender to inherit Dominant Huntington’s disease Li-Fraumeni (LFS) Recessive Humans – Tay Sacs Albinism Treatable for humans Deadly for plants LFS is a hereditary genetic condition. This means that the cancer risk can be passed from generation to generation in a family. This condition is most commonly caused by a mutation (alteration) in a gene called TP53, which is the genetic blueprint for a protein called p53. The mutation takes away the gene’s ability to function correctly. Approximately 70% of families with LFS will have a mutation in the TP53 gene. 20

Inheritance of Sex Chromsomes Mother always give s an X to the offspring Father gives an X or Y to the offspring Most sex-linked traits are on the X chromosome 21

Males are more likely to show Sex Linked Traits Males are more likely to show Males only have one X Examples: Male Pattern Baldness Colorblindness Hemophilia 22

Sex Linked Punnetts Gender must be included for sex linked punnetts. Hemophilia is a sex linked recessive trait. Cross a normal male with a female who is a carrier for hemophilia. 24

Incomplete Dominance occurs when a heterozygous genotype results in an intermediate trait Trait 1 – 2 capital letters Example: red flowers = RR Trait 2 – 2 capital letters Example: white flowers = WW Heterozygous = Mix Example – Pink RW 25

Incomplete Domiance White Seahorse Black Seahorse Gray Seahorse WW BB BW 26

Incomplete Dominance What color are the parents? Gray What color is the top left seahorse? Black What color is the bottom right seahorse? White What color are the BW? 27

Codominance Share dominance CBCW CBCB CWCW Use a capital letter for trait with a different exponent letter to represent each allele CBCW CBCB CWCW 28

Codominance Punnett Cross a speckled chicken with a black chicken. CB CW CBCB CBCW CB CB 29

Traits having >2 allele options Multiple Alleles Traits having >2 allele options Example: Rabbit Coat Color

Multiple Alleles & Codominance Human example: blood types Blood types are A, B, AB, O. A & B are dominant alleles (IA or IB) and O is recessive (i).

Codominance Example: Blood types A B AB O Genotype- IAIA or IAi Fights B or AB Genotype- IBIB Or IBi Fights A or AB Genotype- IAIB Fights None Universal Recipient Genotype- ii Fights all but O Universal Donor 32

How common is your blood type? 46.1% 38.8% 11.1% 3.9%

Blood Type Punnett Cross a man that is heterozygous for B blood with a woman who has AB blood. 34

Blood types

Polygenic Traits Traits produced by the interaction of several genes Example: Human Skin Color 3-6 genes Amount of melanin Incomplete dominance

Eye Color Amount of melanin in iris Chromos. 15 – Brown from Blue Chromos. 19 – green & blue Iris Anterior – front Posterior – back

Environment Affects Nutrition Exercise Heart disease Temperature Gender Determination in reptiles Fur color in rabbits Epigenome Epigenome video Review video AS in picture

Types of Inheritance Inheritance Letters Heterozygous Other Complete # of Dominant Alleles Other Complete A-dominant a- recessive Dominant covers recessive 1 Default Incomplete A – trait 1 B- trait 2 A & B phenotypes will mix Remember to blend the 2 CoDominance Ay – Dom 1 Az – Dom 2 a-recessive Either both show up or if Ay a – dom. 2 Hetero can be both or the dom. Sex Linked XaXa XaY Only female can be hetero Males either have trait or not 39