1. HEREDITY: Going beyond Mendel Individuals don’t always follow the basic pattern of inheritance (dominant/recessive)

2. Many inheritance patterns are more complex: Linked genes Linked genes Incomplete/codominance Incomplete/codominance Multiple alleles Multiple alleles Sex Determination/Sex-linked traits Sex Determination/Sex-linked traits Polygenic Inheritance Polygenic Inheritance Effect of environment on gene expression Effect of environment on gene expression

3. Independent Assortment Recall……..Genes on separate chromosomes will be inherited separately. Recall……..Genes on separate chromosomes will be inherited separately. The way in which chromosomes line up during meiosis is random The way in which chromosomes line up during meiosis is random This adds to variation This adds to variation

4. LINKED GENES Chromosomes carry MANY genes, so some genes will be on the same chromosome. Chromosomes carry MANY genes, so some genes will be on the same chromosome. Genes on the same chromosome are called LINKED genes and are usually inherited together. Genes on the same chromosome are called LINKED genes and are usually inherited together. I say usually because what can happen during Prophase I of meiosis? I say usually because what can happen during Prophase I of meiosis?

5. Incomplete dominance Neither allele completely masks the expression of the other Neither allele completely masks the expression of the other Heterozygous individuals have a different phenotype than either parent Heterozygous individuals have a different phenotype than either parent There is an intermediate phenotype, sometimes called blended inheritance There is an intermediate phenotype, sometimes called blended inheritance

6. Example of incomplete dominance: The snapdragon The snapdragon –The red snapdragon is homozygous and the white snapdragon is also homozygous. The red does not completely mask the white, so a pink phenotype is the result of a cross between red and white. For this cross, we can use different letters: –RR x WW = RW

7. In humans, spacing of eyes and wavy hair are examples of incomplete dominance In humans, spacing of eyes and wavy hair are examples of incomplete dominance

8. Co-dominance Similar to the concept of incomplete dominance. No allele masks the other Similar to the concept of incomplete dominance. No allele masks the other In co-dominance, BOTH traits show in the phenotype In co-dominance, BOTH traits show in the phenotype Example-barred rock chicken is a result of a cross between a black chicken and a white chicken Example-barred rock chicken is a result of a cross between a black chicken and a white chicken

9. Example of co-dominance: In humans, sickle cell anemia In humans, sickle cell anemia as well as types A and B blood show co- dominance as well as types A and B blood show co- dominance

10. Multiple Alleles In some cases, an offspring inherits two alleles from the parent from a choice of three or more alleles In some cases, an offspring inherits two alleles from the parent from a choice of three or more alleles Example is pigeon feather color Example is pigeon feather color Red is dominant to other alleles Blue is recessive to red, dominant to choclate Chocolate is recessive to both Red can AA, Ab or Ac Blue can be bb or bc Chocolate will be cc

11. Examples of multiple alleles: In humans, A, B, o blood types (not the positive/negative factors) In humans, A, B, o blood types (not the positive/negative factors)

12. Cross a father heterozygous for B blood with a mother heterozygous for A blood: I B i x I A i I B i x I A i Bi AAB AiAiAiAi i BiBiBiBiii Type O blood

13. Polygenic Inheritance Inheritance pattern controlled by many genes (do not confuse this with multiple alleles) Inheritance pattern controlled by many genes (do not confuse this with multiple alleles) A trait controlled by polygenic inheritance could have MANY phenotypes A trait controlled by polygenic inheritance could have MANY phenotypes Results will show a bell curve or a continuum Results will show a bell curve or a continuum

14. Example of polygenic inheritance: Height and skin color in humans Height and skin color in humans

16. Sex-linked Inheritance Sex-linked traits are controlled by genes found on a sex chromosome Sex-linked traits are controlled by genes found on a sex chromosome The traits we study are found on the X chromosome. The X chromosome carries different genes than the Y chromosome carries. The traits we study are found on the X chromosome. The X chromosome carries different genes than the Y chromosome carries.

17. Sex-linked traits in humans Include red-green color-blindness and hemophilia Include red-green color-blindness and hemophilia These disorders are found more often in males because they just need one copy of the defective allele to have the disorder. These disorders are found more often in males because they just need one copy of the defective allele to have the disorder. Males do not have another copy of the genes on the X chromosome because they have only one X chromosome. Males do not have another copy of the genes on the X chromosome because they have only one X chromosome.

19. A color-blind son receives the defective gene from his mother:

20. Show a color blind father and a carrier mother pass on their genes:

21. GENE EXPRESSION Gene Expression relates to the presence or dimension of the appearance of a trait for which the genes are present. Gene Expression relates to the presence or dimension of the appearance of a trait for which the genes are present. Internal environment (hormones, nutrition) and external environment (temperature) may have an effect on whether a gene is expressed and if so, how much it is expressed. Internal environment (hormones, nutrition) and external environment (temperature) may have an effect on whether a gene is expressed and if so, how much it is expressed.

22. Examples of gene expression: Horn size in Bighorn sheep Horn size in Bighorn sheep Genotypes are the same, but phenotypes are different, due to ?

23. Gene expression can also be- Affected by temperature, as in a weasel Affected by temperature, as in a weasel He is called an ermine in the winter He is called a stoat in the summer