2History of Genetics Gregor Mendel 1822-1884 “Father of genetics” a monk who studied inheritance traits in pea plansworked with pea plants in the monastery garden
3What Mendel noticed about his pea plants: Pea plants reproduced sexually- with male and female gametesPlants could self-pollinate and short plants bred short plants and tall plants bred tall plants.He studied the following traits: seed color, pod shape, plant height, etc.
4Mendel’s CrossesMendel bred plants with different traits and studied the offspring.original parents are the P generation.offspring were the F1 (daughter/son) generation
5Mendel’s conclusions Law of Inheritance Law of dominance Traits are controlled by pairs of genes- with one member of each pair coming from each parentLaw of dominancesome alleles are dominant and other are recessive.Dominant – expressedRecessive – present but not expressed
6Mendel’s Laws Continued Law of Segregation and RecombinationDuring gamete formation two chromosomes separateEach gamete contains one allele for each traitLaw of Independent AssortmentTraits are inherited independently of each other
7Key TermsGeneSections of giant DNA molecules found in chromosomesAre the units of heredityAlleleAlternative genes for traitExample: Height: Tall or Short; Eyes: Brown or Blue; Cheeks: Dimple or No Dimple; Hair Line: Widows or Straight
8D/R Each gene has two possible alleles Dominant- always expressed Recessive- always hidden by a dominant allele.Example: Dimpled chin (cleft chin)D= dimpled d= non-dimpled
9More terms: Homozygous / Pure Heterozygous / Hybrid Phenotype Genotype having 2 of the same allelesexample: DD – homozygous dominant dd – homozygous recessiveHeterozygous / Hybridhaving 2 different alleles ex: DdPhenotypephysical characteristic ex: dimpled chinGenotypegenetic make up ex: DD
10Punnett Square Used to predict the possible offspring of a couple. Gives the probability of the mating- not the actual outcome
11Punnett Square Rules Define traits, assign symbols Determine the parental genotypesSet up Punnett squareWork it outList the genotype probabilityList the phenotype probability
12PracticeIn humans a widow’s peak is dominant over a straight hairline. A man who is heterozygous for widow’s peak married a woman without a widow’s peak. Predict the genotype and phenotype of the offspring:
13In humans, the ability to tongue roll is dominant over not being able to tongue roll. Cross a heterozygous man with a non-rolling woman. List the possible genotypes and phenotypes of the offspring.
14In humans, brown eyes are dominant over blue eyes In humans, brown eyes are dominant over blue eyes. Cross a homozygous dominant man with a blue eyed woman. List the possible genotypes and phenotypes of the offspring.
15In guinea pigs, black hair is dominant over brown hair In guinea pigs, black hair is dominant over brown hair. Cross two guinea pigs that are heterozygous for black hair. What are the chances their offspring would have brown hair?
16Intermediate Inheritance Incomplete Dominancea type of heredity in which the hybrid is an intermediate between the pure dominant and recessive parents. (Blending of trait) ExampleCo-dominanceexpression of two dominant alleles (spots, strips, etc) Example
17Example of Incomplete Dominance A Japanese 4 o’clock flower can be red, white, or pink. Pink is the result of the mixture of red and white. Cross two pink flowers. List their genotypes and phenotypes.RR = Red WW = White RW = Pink
18Example of Co-dominance Shorthorn cattle can have one of three color coats. Their coats can be red, white or roan. Roan is patches of red and white hairs. Cross a roan bull with a red cow.CRCR = Red Hair CWCW = White Hair CRCW = Roan
19Multiple Allelessome traits have more than one allele, but a single individual cannot have more than two genes for a each traitExample: Human Blood TypeType AType BType ABType O
20Can you Write out the Key? Type A and B are co-dominantType O is recessive
21Blood Type Key Phenotype Type A Type B Type AB Type O Genotype IAIA IAiOIBIBIBiOIAIBiOiO
22Practice: Multiple Alleles The ABO blood group system in humans is an example of multiple alleles. Cross a heterozygous type A male with a heterozygous type B female. Record the possible genotypes and phenotypes.
23Cross a person with type AB blood and a person who is heterozygous for type B blood. What are the chances the child will have type A blood?
24What must the genotypes of a parent with type A blood and a parent with type B blood be if they have a child with type O blood?
25Sex Linked Traits Sex Determination Sex Linked Trait Female: XX Male: XYThe sperm cell determines the sex of the childSex Linked TraitThe gene found only on the X or Y chromosomeMales tend to be more vulnerable to sex-linked genetic disorders because most disorders occur on the X chromosome
26Practice: Sex Linked Traits In humans, hemophilia is a sex linked trait. Females can be normal, carriers, or have the disease. Males will either have the disease or not (but they won’t ever be carriers). Cross a male with hemophilia with a carrier female. List genotypes and phenotypes.