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Theoretical Genetics

Theoretical Genetics. 4.3.2-4.3.11 Sydney Foil, Jasmine Delaine, Cameron Folmar, Stephanie Weng. Genotypes and Phenotypes . Alleles: one member of a pair of genes that codes for distinct traits Genotypes: the alleles of an organism Phenotypes: the characteristics of an organism.

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Theoretical Genetics

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  1. Theoretical Genetics 4.3.2-4.3.11 Sydney Foil, Jasmine Delaine, Cameron Folmar, Stephanie Weng

  2. Genotypes and Phenotypes • Alleles: one member of a pair of genes that codes for distinct traits • Genotypes: the alleles of an organism • Phenotypes: the characteristics of an organism

  3. Genotypes and Phenotypes • The genotypes of offspring can determined using a monohybrid cross • A monohybrid cross is a genetic cross using a single trait with two alleles (both heterozygous)

  4. Phenotype Ratios • Using punnett squares you can find out the ratio of phenotypes.

  5. Activity • Punnett square worksheet • Work in groups of two or three

  6. Genes Have Multiple Alleles • Some genes can have more than just two alleles. • Although these genes can have multiple alleles individuals can only have two. • Example: the gene of the A, B, AB, and O blood types. This gene contains three alleles.

  7. Codominance and Multiple Alleles • The alleles of IA and IB are dominant while the i is recessive. • When both dominant alleles are present they form the blood group AB • Codominant alleles are pairs of alleles that both affect the phenotype when present in the heterozygote.

  8. Determining Gender • The mother always passes on an X chromosome to her offspring • The father can pass either an X or Y chromosome to his offspring • Some genes are present on the X chromosome and absent from the shorter Y chromosome in humans

  9. Sex Linkage • When the gene controlling the characteristic is located on the sex chromosome • We associate the characteristic with gender • Sex-linked genes are carried on the X chromosome • Because females have two X chromosomes, they carry two copies of the sex-linked gene while the males only carry one because they only have one X chromosome. • Example: Hemophilia and color blindness

  10. Sex Linkage Continued • Hemophilia: XH is the allele for normal blood clotting, this is dominant over the allele Xh (the recessive gene which causes hemophilia) • If the mother is heterozygous, she is then a carrier of the disease and passes it on to her offspring • This means the dominant and recessive alleles are present.

  11. Heterozygous or Homozygous • Heterozygous: contains two different alleles • Ex: Rr (one recessive, one dominant) • Ex: AB blood type • Homozygous: having identical alleles for the same trait • Ex: RR or rr

  12. Heterozygous or Homozygous • Because a female has two X chromosomes she can carry either both recessive/dominant genes or she can have one of each (with respect to sex linked genes). • If female carriers are heterozygous they can pass it onto their offspring.

  13. Game Time • Basketball: • Six teams of five each • Each team at a lab table • Write answer on white board • Get the question right first, chance to shoot

  14. Works Cited • "IB Biology Notes - Theoretical Genetics." IB Guides - Free International Baccalaureate Study Guides, Notes, Videos and Powerpoints. 2010. Web. 10 Feb. 2012. <http://www.ibguides.com/biology/notes/theoretical-genetics>. • "Multiple Alleles." Redirecting... Web. 10 Feb. 2012. <http://www.hobart.k12.in.us/jkousen/Biology/multalle.htm>. • Pitocchelli, Jay. "Lecture Notes for Genetics." Saint Anselm College : Saint Anselm College. 2001. Web. 10 Feb. 2012. <http://www.anselm.edu/homepage/jpitocch/genbio/geneticsnot.html>. • "X and Y Chromosomes." Science Photo Library. Web. 10 Feb. 2012. <http://www.sciencephoto.com/media/94963/view>.

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