What’s the difference between a phenotype and a genotype? Agenda for Friday Jan 30 th 1.Go over HW...
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![Page 1: 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.](https://reader035.fdocuments.us/reader035/viewer/2022062422/56649e8f5503460f94b93218/html5/thumbnails/1.jpg)
What’s the difference between a phenotype and a genotype?
Agenda for Friday Jan 30th 1. Go over HW (Dihybrid)2. Incomplete and codominance
![Page 2: 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.](https://reader035.fdocuments.us/reader035/viewer/2022062422/56649e8f5503460f94b93218/html5/thumbnails/2.jpg)
Complete Dominance
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Purebred red snapdragons were crossed with purebred white snapdragons all offspring were pink
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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
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Co-dominance• In COdominance, both traits appear together in
the phenotype of hybrid (heterozygous)
WHITE RED
ROAN
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PracticeSet 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.
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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?
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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?
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Agenda for Monday Feb 2nd 1. Go over Incomplete/codominance wkst2. 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?
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Sex Determination
• Thomas Hunt Morgan – studied fruit flies in the early 1900’s
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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
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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
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Fruit Fly Eye Color
• Fruit flies normally have red eyes– Red is dominant; white is recessive
• A few males have white eyes
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Morgan’s Fruit Fly Experiments
• Red-eyed female (XRXR) x White-eyed male (XrY)
XR XR
Xr
Y
XRXr XRXr
XRY XRY
RESULTS:
F1 generation – all red-eyed
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Morgan’s Fruit Fly Experiments
• Red-eyed female (XRXr) x Red-eyed male (XRY)
XR Xr
XR
Y
XRXR XRXr
XRY XrY
RESULTS:
F2 generation – 3 red-eyed and 1 white-eyed
** all white-eyed where males…why?
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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 = XRXR, XRXr , XRY• White-eyed = XrXr, XrY
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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?
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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?
![Page 19: 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.](https://reader035.fdocuments.us/reader035/viewer/2022062422/56649e8f5503460f94b93218/html5/thumbnails/19.jpg)
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?
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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?
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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 4th 1. Disorder project
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What is meant by a sex-linked trait?
Agenda for Thursday Feb 5th 1. Go over HW2. Multiple alleles
Quiz tomorrow
Projects due Monday
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Multiple Alleles• Multiple alleles – traits
determined by more than 2 alleles– Increases possible number of
genotypes & phenotypes– Blood groups
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Blood Types• A,B,O blood types• A and B are dominant over O
– Co-dominant to each other• O blood type is recessive
GENOTYPEIAIA IAi
RESULTING PHENOTYPES Type A Type A
IBIB IBi
Type B Type B
IAIB Type AB ii Type O
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• More alleles means more combinations• 6 different genotypes & 4 different phenotypes
• 2 genotypes for both "A" & "B" blood --- either homozygous (IAIA or IBIB) or heterozygous with one recessive allele for "O" (IAi or IBi).
• 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?
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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?
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One More
• What are the chances of a woman with Type AB and a man with Type A having a child with Type O?
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Complete dominance - 2 traitsBB Bb bb**Homozygous dominant same as heterozygousIncomplete Dominance – 2 different lettersRR WW RW ** heterozygous is a blend of other 2 traitsCo-dominance - 2 different letters GG TT GT **heterozygous see both of the other 2 traitsSex Linked Traits – use X’s and Y’s **no gene on YMultiple alleles – blood type, use I’s
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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 6th 1. Quiz2. Finish notes3. Disorders
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Epistasis• Epistasis – one allele hides/suppresses another allele
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Polygenic• Phenotype depends on alleles in multiple
genes– Skin color, height, eye color– Continuous progression in expression of traits
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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!
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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
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Environmental Influences
• Inherit tendency of getting heart diseases– Diet/exercise can also
influence
• Water/ temperature/ sunlight effect plants
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Agenda for Tuesday April 29th 1. Sex Linked traits (go over HW)2. Multiple alleles3. Epistasis/polygenic4. 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?