Unit 4 – Lecture 7

Review Mendellian / Single-Gene Inheritance two alleles per gene = 1 dominant, 1 recessive ex: R = red, r = blue RR = red Rr = red rr = blue COLOR THE IMAGES ON YOUR LECTURE NOTES

Discuss What does it mean to be “incomplete” ? [don’t say – to not be complete…think about this]

Incomplete Dominance two dominant alleles present BLEND of alleles is expressed when combined uses same letter with “prime” or another letter as exponent can have a recessive allele still – which is hidden by BOTH of the dominant alleles if present. A 1

Incomplete Dominance – cont’d Incomplete Dominance ex: R = red, R 1 = blue RR = red RR 1 = PURPLE R 1 R 1 = blue COLOR THE IMAGES ON YOUR LECTURE NOTES

Codominance two dominant alleles present BOTH alleles are expressed when combined offspring show both phenotypes at same time uses same letter with “prime” or another letter as exponent can have a recessive allele still – which is hidden by BOTH of the dominant alleles if present.

Codominance – cont’d Codominance ex: R = red, R 1 = blue RR = red RR 1 = red AND blue [striped, spotted, checkered, etc] R 1 R 1 = blue COLOR THE IMAGES ON YOUR LECTURE NOTES

Multiple Alleles trait is coded for by more than 2 alleles for the SAME gene [same letter!!] more combinations for the same trait gene can have: multiple dominant alleles – like codominant or incomplete dominance multiple recessive alleles – all of which would be hidden by any dominant allele present

MA Example - Discuss Example: three alleles for the “R” gene R = redR 1 = white r = orange What color phenotypes would result from each of the following genotypes? [assume co-dominance] RR RR 1 R 1 R 1 Rr R 1 rrr red white red AND white red orange

Multiple Alleles – cont’d Multiple Alleles ex: Blood Type – codominant multiple allele trait alleles = I A, I B & i o A and B are dominant, O is recessive caps letter “I”lower-case letter “i”

MA – Discuss So…if A [I A ] and B [I B ] are dominant, and O [i o ]is recessive … which genotypes will give each blood-type phenotype? [A, B, and O] A blood: I A I A or I A i o B blood: I B I B or I B i o O blood: only i o i o

NOTE You MAY NOT do blood type as your multiple allele trait. Your traits must ALL be able to be seen just by looking at your creature.

Polygene Inheritance “poly” = many traits are influenced by many genes will have combinations of different letters ex: traits with ranges or many types hair/eye/skin color, height, build, etc.

Polygene Inheritance ex: A / G / R = red a / g / r = no red more dominant alleles, more color Aa Gg Rr is darker red than Aa gg rr

Naming Inheritance Types of Chromosomes Autosome = non-sex determining chromosome [1-22] “autosomal” trait = trait on a non-sex chromosome Sex-Chromosome = X or Y, chromosome pair #23 “sex-linked” trait = trait on the X or Y [sex] chromosome

Naming Inheritance Autosomal Dominant dominant trait on a non-sex chromosome heterozygotes [Aa] and dominant homozygotes [AA] have the trait children with trait have at least one parent with the trait affects males and females equally

Naming Inheritance Autosomal Recessive recessive trait on a non-sex chromosome must be recessive homozygote [aa] to have the trait children with trait have parents who either show or carry the trait carrier – heterozygote person for a recessive trait – does not show it, but has the allele [Aa] if both parents have the trait, ALL children will have the trait

Naming Inheritance Autosomal Recessive affects males and females equally traits often skip generations

Naming Inheritance Sex-linked Dominant [X A ] dominant trait on a sex chromosome typically on the X-chromosome many are fatal [especially in males] if both parents have trait, most children will have it ¾ of children if heterozygous mother all children if homozygous mother affects males and females equally if both parents have it, all kids have it.

Naming Inheritance Sex-linked Recessive [X a ] recessive trait on a sex-chromosome typically on the X-chromosome females can be carriers; males cannot affects more males than females son with trait can have parents who don’t show trait no father to son transmission of trait traits often skip generations