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 Worked with pea plants Studied various traits Trait – genetically determined characteristic or condition

Alleles Different forms of the same gene Example: Hair color

Generations P(parental) = original pair F1(1 st filial) = P offspring –Filius = Latin for “son” F2 (2 nd filial) = F1 offspring

First Experiment P (parental) F1

Second Experiment F1 F2

Gregor Mendel Four major conclusions: 1.Inheritance factors 2.Principle of Dominance 3.Law of Segregation 4.Law of Independent Assortment

Mendel’s Conclusion 1.Inheritance is determine by factors passed down by parents *factors = genes

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

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

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 Mendel’s Conclusions

Punnett Square Monohybrid 1 trait Dihybrid 2 traits

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

Example 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

Example Cross t t T tt Tt tt Tt t

Probability Predict the chance of each phenotype’s occurrence Think of each little square as a quarter Think of each large square as a dollar 25 = 100

Example Cross t t T tt Tt tt 50% t Tt 50%

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

Dihybrid Examines two traits Shows independent assortment Pea Plants Round seeds (R) are dominant to wrinkled (r) Yellow seeds (Y) are dominant to green (y) How many traits are we looking at? So how many alleles per parent? So how many alleles per gamete? 4 2 2

Finding Gametes? FOIL F – first O – outer I – inner L – last RrYy F – RY O – Ry I – rY L – ry

Lethal Inheritance Inherited allele may cause death Prolonged –Huntington’s disease Immediate –Humans – Tay SacsTay Sacs –Plants - Albino

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

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

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? –Gray

Codominance Share dominance CBCBCBCB CWCWCWCW CBCWCBCW Use a capital letter for trait with a different exponent letter to represent each allele

Codominance Punnett Cross a speckled chicken with a black chicken. CBCBCBCB CBCWCBCW CBCBCBCB CBCWCBCW CBCB CBCB CBCB CWCW

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

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

Codominance Example: Blood types ABABO Genotype- I A I A or I A i Fights B or AB Genotype- I A I B Fights None Universal Recipient Genotype- I B I B Or I B i Fights A or AB Genotype- ii Fights all but O Universal Donor

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.

Blood types

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

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

Nutrition Exercise Heart disease Epigenome Environment Affects

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

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

Sex Linked Traits Males are more likely to show –Males only have one X Examples: Male Pattern Baldness ColorblindnessHemophilia

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.

Types of Inheritance InheritanceLettersHeterozygous # of Dominant Alleles Other CompleteA-dominant a- recessive Dominant covers recessive 1Default IncompleteA – trait 1 B- trait 2 A & B phenotypes will mix 0Remember to blend the 2 CoDominanceA y – Dom 1 A z – Dom 2 a-recessive Either both show up or if A y a – dom. 2Hetero can be both or the dom. Sex LinkedXaXaXaYXaXaXaY Only female can be hetero 1Males either have trait or not