Presentation on theme: "Genetics The study of potentials of passing information from one generation to the next."— Presentation transcript:
1GeneticsThe study of potentials of passing information from one generation to the next
2Gregor Mendel “Father” of genetics Studied pea plants Used contrasting featuresParents “bred true”Kept good recordsStudied one trait at a time
3Mendel’s pea experiment True breeding purple flower plantsTrue breeding white flower plantsF1 generationF2 generation
4Terminology Gene – unit of inheritance made of DNA Genes occur in pairs except in the egg and spermAn allele is a different form of the same geneBlack hair and brown hair are alleles of the hair color gene
5GenesDominant gene is one that can overshadow another gene. Signified with capital letter, e.g. “A”Recessive gene is the subordinate gene that can be suppressed by the dominant gene. Signified with a lower-case letter, e.g. “a”
6GenesHomozygous – since genes occur in pairs, this is when both genes for the trait are the sameAA is homozygous dominantaa is homozygous recessive
7Genes Heterozygous – genes are alleles or different for a given trait Aa is heterozygousCarrier is sometimes used to indicate that someone is heterozygous
8Genes Genotype is your genetic makeup For example, you might be heterozygous for hair color, Bb, one gene for black hair, and one for blonde hair
9Genes Phenotype is your physical appearance Your phenotype for hair color may be brown
10One gene problem Let P = Purple flower plants, or Let p = white flower plants, orThe parent generation included true breeding purple flower plants that must have been PP (homozygous dominant) in genotypeThe parent generation included true breeding white flower plants that must have been pp (homozygous recessive) in genotype
11ParentsPP plant can only make a gamete with the first “P” gene, or the second “P” gene(See example using E instead of P)pp plant can only make a gamete with its first “p” gene, or the second “p” gene(See example using e instead of P)
13F1 generationIf these two parents fertilize to create offspring, F1, or first generation, what genotypes and phenotypes would be possible in the F1 generation?Use a mathematical Punnet square to find the probabilities
14F1 generation Gamete with “P” gene – parent 1 Offspring is heterozygous – “Pp”
15F1 generation100% of the offspring would have a genotype of Pp, or be heterozygous100% of the offspring would have a phenotype of purple flowers, since purple is dominant over white
16F2 generationIf you take two plants from the F1 generation (Pp) and cross them, what would be the genotypic and phenotypic ratios of the next, or F2 generation?
17F2 generation Gamete with “P” gene – parent 1 Offspring is homozygous dominant – “PP”Offspring is heterozygous – “Pp”Gamete with “p” gene – parent 2Offspring is homozygous recessive – “pp”
18F2 generationNote that the four squares in the Punnet square do not represent four different offspring, but rather the statistical chances that any ONE offspring has a given traitGenotypic ratios are 1 homozygous dominant : 2 heterozygous : 1 homozygous recessivePhenotypic ratios are 3 purple : 1 white
19Try this problem E = unattached earlobes e = attached earlobes Problem one: Both parents have unattached earlobes. However, they had a son with attached earlobes. What are the chances that their next child will have unattached earlobes?
23Try this problem E = unattached earlobes e = attached earlobes Problem two: One parent has unattached earlobes and the other has attached earlobes. They had a daughter with attached earlobes. What are the genotypes of the parents? What are the chances that their next child will have unattached earlobes?
25Autosomal DominantThe trait or disease is the result of a dominant gene
26Autosomal RecessiveThe trait or disease is the result of a recessive gene (e.g. cystic fibrosis)
27Incomplete dominanceThe dominant gene is not strong enough to completely overshadow the recessive geneExample: If a red flower plant (dominant) crosses with a white flower plant (recessive) and the offspring have pink flowers (heterozygous).
28Codominance No clear dominant or recessive gene Genes are equal, or codominantIf genes for blood type A and blood type B are codominant and you have one gene of each, your blood type is AB
29Blood typing practiceGenes for blood types A and B are dominant over type OGenes for blood types A and B are codominant with each otherIf mom has blood type A and dad has blood type B, and they have a son with blood type O, what are the genotypes of these 3 people? What are the statistical chances that their next child has blood type AB?
31Sex-Linked traitsThe sex of the person has not mattered up until this point working on the genetics problems. Now it does.These sex-linked problems are such that the gene for the particular trait is located on the X chromosome only.Recall that males are XY and females are XX.
33Colorblindness is sex linked Colorblind is a recessive traitCarried on the X chromosome onlyLet B = normal vision and b = color blindMom and dad both have normal vision. However, their second child was a colorblind son. What are the genotypes of the parents and what are the chances that their next son/daughter is colorblind?