Presentation on theme: "More Punnett squares. Complete Dominance Involves dominant and recessive alleles dominant allele always overpowers the recessive allele in appearance."— Presentation transcript:
More Punnett squares
Complete Dominance Involves dominant and recessive alleles dominant allele always overpowers the recessive allele in appearance
Incomplete Dominance Neither allele is dominant or recessive Organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parents
Incomplete Dominance Ex: Cross a red flower (RR) with a white flower (WW) and the offspring will be pink (RW)!
Incomplete Dominance In another flower, if red ____ and blue ____ flowers are crossed, they produce a 3 rd purple ____ flower What would be the genotypic ratio and phenotypic ratio if you crossed two purple flowers? (RR) (RB) (BB)
Incomplete Dominance Cross of two purple flowers _RB_ X _RB_ What are gamete possibilities? genotypic ratio 1RR : 2RB : 1BB phenotypic ratio 1red : 2 purple : 1 blue RR red RB purple RB purple BB blue R B B R
Codominance Neither allele is dominant or recessive Parents with different phenotypes produce an offspring with a third phenotype – Third phenotype will show both parental phenotypes simultaneously (at the same time)
Codominance In cattle and horses, if you cross a pure red (RR) with a pure white (WW), you get (RW) which produces the color roan.
Codominance These cattle or horses actually have both red and white hairs intermixed, or are spotted. Roan is a third phenotype. If you cross a roan with a white… RW X WW RW roan WW white RW roan WW white R W W W
What is it?! + = + =
Multiple alleles two or more possible alleles for the same gene within a population Thus multiple alleles However, individuals within the population are only able to hold two of them Non-human examples: rabbit fur color, mice skin color, eye color in flies, wing size in flies
Multiple Alleles Blood type in humans The _four_ different blood types: – A, B, O, and AB Blood types are produced by three_ different alleles: – A, B and O PhenotypeGenotype AAA or AO BBB or BO ABAB only OOO only
Genotype for Blood Type I and i used in genotype I used with A and B i used with O A and B are dominant over O: A and B are codominant Ex: Genotype: AA is I A I A
Blood type chart PHENOTYPEGENOTYPE AAA, I A I A AAO, I A i BBB, I B I B BBO, I B i ABAB, I A I B OOO, ii Blood type AB is an example of codominance in humans
Blood Type Punnett Square Draw a Punnett square showing all the possible genotypes for the offspring produced by a type O mother and an a Type AB father. Cross: ii x I A I B IAiIAiIAiIAi IBiIBiIBiIBi ii IAIA IBIB
Blood Type Punnett Square Cross a female with blood type A and a male with heterozygous B blood type. Complete ratios (phenotypic and genotypic) A male with blood type B has a child with a woman who has blood type A. The child is blood type O. What is the genotype of the male and female? Show your work.
How does blood type work?
Rh factor: Rh for Rhesus Monkey Positive vs Negative Blood types Positive: protein is present Dominant trait Negative: protein is absent Recessive trait
Polygenic traits Traits controlled by two or more genes (one gene has two alleles) Show a wide range of phenotypes Phenotype is produced by the interaction of more than one pair of alleles
Examples of polygenic traits in humans
Example of polygenic traits in humans
Examples of polygenic traits in humans
Sex-linked traits Every new born has a 50% chance of being female and a 50% chance being male – DAD: X Y Sperm contains either: – MOM: X X Eggs all contain: YX X or XXXY XXXY X X X Y
Sex-Linked traits The X chromosome contains many genes, whereas the Y chromosome contains only a few genes sex-linked genes: genes located on one of the sex chromosomes (X or Y) but not the other most sex-linked genes are X-linked genes
Examples of sex-linked traits: X-linked Colorblindness: more common in males than females Hemophilia: more common in males than females Both colorblindness and Hemophilia are recessive traits
Do any of these pictures look the same?!
Colorblind: X-linked trait C - normal vision c- colorblind You must incorporate XX (mom) and XY (dad) This is how to set it up: (remember colorblindness is X-linked!) Normal vision Heterozygous (carrier) Colorblind Female: XX Male: XY
Punnett Square Cross a female who is a carrier for colorblindness with a normal vision man. Cross a normal vision woman (homozygous) with a colorblind man.
Hemophilia: X-linked recessive trait Hemophilia is the inability for blood to clot – Your blood clots every time you get a papercut – H : normal clotting – h: hemophilia – Make a key for hemophilia: Normal female:Normal Male: Female Carrier:Can a man be a carrier? Female with hemophilia: Male with: