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the activity of other genes

“Nature vs. Nurture” Environment and Gene Expression Gene expression can be affected by many factors, including:. the activity of other genes climate conditions – Ex.: Siamese cat & Himalayan rabbit fur, flower color in hydrangeas, etc.

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the activity of other genes

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  1. “Nature vs. Nurture”Environment and Gene ExpressionGene expression can be affected by many factors, including: • the activity of other genes • climate conditions – Ex.: Siamese cat & Himalayan rabbit fur, flower color in hydrangeas, etc.

  2. “Nature vs. Nurture”Environment and Gene ExpressionGene expression can be affected by many factors, including: • social environment of organism – Ex.: Japanese goby fish changes sex depending on the gender of other fish present

  3. “Nature vs. Nurture”Environment and Gene ExpressionGene expression can be affected by many factors, including: • internal environment of organism – diet (presence of nutrients) affects height; shyness in children is affected by socialization; • External environment of organism – Ex.: Mutagens/carcinogens – cancer development

  4. Refining Mendel’s LawsLinked Genes • Genes located on the same chromosome travel together into the same gamete; • the two traits are inherited together, instead of sorting independently • this is an exception to Mendel’s law of independent assortment.

  5. Intermediate Inheritance:Polygenic Traits Most traits are polygenic – affected by more than one gene.

  6. Intermediate Inheritance: Incomplete Dominance – “no win” Result of incomplete dominance: blending of traits in heterozygote

  7. Intermediate Inheritance:Codominance – “win-win” Codominance - both alleles in heterozygote express themselves fully Ex.: blood types are determined by carbohydrates (sugars) on red blood cells; two alleles  two types of carbohydrate molecules on RBCs. Human blood types also havemultiple alleles (more than two): IA, IB and i (neither) Rh factor (a different gene) (+, dominant or -, recessive) also determines blood type; ex.: A+, B-, etc. Blood transfusions - People reject any blood factor they do NOT have. B A A B B A

  8. A Anti-B A and AB AA or AO A A B Anti-A BB or BO B and AB B B A B None AB AB B A B A Anti-A Anti-B All Blood Types OO

  9. Sex-Linked Traits • & • Sex-Influenced Traits • * Add the missing examples • to your notes. *

  10. Which sex has more chromosomes? Which sex has more genes?

  11. It starts at a young age and men just get worse But wait! Things are not as bad as they seem… 

  12. X Inactivation( A.K.A. Revenge for Boys!  ) • Early in embryonic development in females, one of the two X chromosomes is randomly and permanently inactivated in cells other than egg cells. • This ensures that females, like males, have one functional copy of the X chromosome in each body cell. • Some genes on the X chromosome escape X-inactivation. Many of these genes are located at the ends of each arm of the X chromosome in areas known as the pseudoautosomalregions. • Although many genes are unique to the X chromosome, genes in the pseudoautosomal regions are present on both sex chromosomes, and many are essential for normal development.

  13. Tortoiseshell / Calico Cat Primary gene for coat color on the X chromosome has two co-dominant alleles,Orange (XO) & Black (XB) X inactivation (random) in different embryonic cells (melanocytes) produces the pattern Delayed melanocyte migration during development (another gene does this) creates white in the three-color cats (cells w/o pigment) Male or female? Females, except for rare XXY males

  14. Two cell populationsin adult Early embryo Cell divisionand randomX chromosomeinactivation Orangefur X chromosomes Active X Inactive X Inactive X Allele fororange fur Active X Black fur Allele forblack fur Figure 11.5

  15. Sex-Linked Traits • Colorblindness • Hemophilia Linked to X chromosome, are recessive

  16. Sex-Linked Traits Sex-linked traits are encoded by genes on the X or Y chromosomes. Ex.: Hemophilia, a defect in blood clotting, is a recessive, X-linked trait (Xh) found mostly in boys. *Since the Y chromosome does not have the gene for the blood clotting factor, this boy has no good copy of the gene and has the recessive phenotype.

  17. Hairy Pinna Linked to Y chromosome

  18. Sex Influenced Trait Gene is on an Autosome (#1 - #22), but the Phenotype is INFLUENCED by the SEX HORMONES which are controlled by the SEX CHROMOSOMES

  19. Sex Influenced Traits Male Patterned Baldness

  20. Sex Influenced Trait MaleFemale PhenotypePhenotype Hair Hair BB B’B B’B’ Patterned Baldness Hair Patterned Baldness Patterned Baldness

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