What’s the difference between a phenotype and a genotype? Agenda for Friday Jan 30 th 1.Go over HW (Dihybrid) 2.Incomplete and codominance

Complete Dominance

Purebred red snapdragons were crossed with purebred white snapdragons all offspring were pink

Incomplete Dominance one allele for a trait is not completely dominant over the other allele Combined (blended) phenotype R = allele for red flowers W = allele for white flowers red x white ---> pink RR x WW ---> 100% RW

Co-dominance In COdominance, both traits appear together in the phenotype of hybrid (heterozygous) WHITERED ROAN

Practice Set up genotypes for the phenotypes listed in each set. Remember that the "medium" trait is always heterozygous. a) Birds can be blue, white, or white with blue-tipped feathers. b) Flowers can be white, pink, or red. c) A Hoo can have curly hair, spiked hair, or a mix of both curly and spiked.

1. Write the genotypes for the pictured phenotypes 2. Show the cross between a star-eyed and a circle eyed. What are the phenotypes of the offspring? What are the genotypes?

3. Show the cross between a circle-star eyed, and a circle eyed. How many of the offspring are circle-eyed? How many of the offspring are circle-star eyed? Write the genotypic and phenotypic ratios. 4. Show the cross between two circle-star eyed. How many of the offspring are circle-eyed? How many of the offspring are circle-star eyed? How many are star eyed?

Agenda for Monday Feb 2 nd 1. Go over Incomplete/codominance wkst 2. Sex linked traits In humans, straight hair and curly hair are incompletely dominant traits that result in hybrids that have wavy hair. Cross a straight hair with a wavy hair. What are the chances of having a curly haired child? What are the chances of having a straight hair child?

Sex Determination Thomas Hunt Morgan – studied fruit flies in the early 1900’s

Sex Determination Observed that one pair of chromosomes was different between males and females – Large one named “X” chromosome – Smaller one named “Y” chromosome – XX = female; XY = male

Sex Linkage Sex Linkage: the presence of a gene on a sex chromosome (X or Y) X-linked genes: genes found on the X chromosome – X chromosome carries more genes Y-linked genes: genes found on the Y chromosome

Fruit Fly Eye Color Fruit flies normally have red eyes – Red is dominant; white is recessive A few males have white eyes

Morgan’s Fruit Fly Experiments Red-eyed female (X R X R) x White-eyed male (X r Y) XRXR XRXR XrXr Y XRXrXRXr XRXrXRXr XRYXRYXRYXRY RESULTS: F 1 generation – all red-eyed

Morgan’s Fruit Fly Experiments Red-eyed female (X R X r) x Red-eyed male (X R Y) XRXR XrXr XRXR Y XRXRXRXR XRXrXRXr XRYXRYXrYXrY RESULTS: F 2 generation – 3 red-eyed and 1 white- eyed ** all white-eyed where males…why?

Morgan’s Conclusions Gene for eye color is carried on the X chromosome = eye color is an X-linked trait Y chromosome does not carry a gene for eye color Red-eyed = X R X R, X R X r, X R Y White-eyed = X r X r, X r Y

In humans colorblindness (b) is an example of a sex-linked recessive trait. A male without colorblindness marries a female who isn’t colorblind but carries the allele. 1.How many females will be colorblind? 2.What sex will any colorblind children be? 3.What percent will be male and colorblind?

In fruit flies red eye color (R) is dominant to white eyes (r) and is a sex linked trait. A heterozygous red eye female mates with a red eye male. 1.How many will have red eyes? 2.What percent will have white eyes? 3.How many will be female and red eyed?

In fruit flies red eye color (R) is dominant to white eyes (r) and is a sex linked trait. A homozygous red eye female mates with a white eye male. How many males will have white eyes?

In humans colorblindness (b) is an example of a sex-linked recessive trait. A male with colorblindness marries a female who isn’t colorblind and does not carry the allele. What is the chance they will have a child that is colorblind?

In humans colorblindness is an example of a sex- linked recessive trait. A male with colorblindness marries a female who is a carrier. What is the chance they will have a child that is colorblind? Agenda for Wednesday Feb 4 th 1.Disorder project

What is meant by a sex-linked trait? Agenda for Thursday Feb 5 th 1.Go over HW 2.Multiple alleles Quiz tomorrow Projects due Monday

Multiple Alleles Multiple alleles – traits determined by more than 2 alleles – Increases possible number of genotypes & phenotypes – Blood groups

Blood Types A,B,O blood types A and B are dominant over O – Co-dominant to each other O blood type is recessive GENOTYPE I A I A I A i RESULTING PHENOTYPES Type A Type A IBIBIBiIBIBIBiType B IAIBIAIB Type AB ii Type O

More alleles means more combinations 6 different genotypes & 4 different phenotypes 2 genotypes for both "A" & "B" blood --- either homozygous (I A I A or I B I B ) or heterozygous with one recessive allele for "O" (I A i or I B i). The only genotype for "O" blood is homozygous recessive (ii). And lastly, what's the deal with "AB" blood? The "A" trait & the "B" trait appear together in the phenotype. What is this an example of?

Problems A woman with Type O blood and a man who is Type AB have are expecting a child. What are the possible blood types of the kid? What are the possible blood types of a child who's parents are both heterozygous for "B" blood type?

One More What are the chances of a woman with Type AB and a man with Type A having a child with Type O?

Complete dominance - 2 traits BBBbbb **Homozygous dominant same as heterozygous Incomplete Dominance – 2 different letters RRWWRW ** heterozygous is a blend of other 2 traits Co-dominance - 2 different letters GGTTGT **heterozygous see both of the other 2 traits Sex Linked Traits – use X’s and Y’s **no gene on Y Multiple alleles – blood type, use I’s

What are the chances of a woman with Type AB and a man with Type O having a child with Type O? Agenda for Friday Feb 6 th 1.Quiz 2.Finish notes 3.Disorders

Epistasis Epistasis – one allele hides/suppresses another allele

Polygenic Phenotype depends on alleles in multiple genes – Skin color, height, eye color – Continuous progression in expression of traits

Another example of a polygenic trait: Hair Color – Hair color is controlled by alleles on chromosomes 3, 6, 10, and 18. – The more dominant alleles that appear in the genotype, the darker the hair!

Eye Color Has to do with the amount of melanin – More melanin = darker eyes Multiple genes determine how much melanin – More dominant genes = more melanin Heterochromia = different color eyes – uneven distribution of melanin

Environmental Influences Inherit tendency of getting heart diseases – Diet/exercise can also influence Water/ temperature/ sunlight effect plants

Agenda for Tuesday April 29 th 1. Sex Linked traits (go over HW) 2. Multiple alleles 3. Epistasis/polygenic 4. Talk about disorder project In fruit flies red eye color (R) is dominant to white eyes (r) and is a sex linked trait. Cross a heterozygous female with a white eye male. How many will be red eye and male?