Download test cross

Review:
What is a phenotype?
What is a genotype?
How many copies of each gene does an individual have?
Where does an individual get each copy of their gene?
Using the letter Q or q
show the genotype for heterozygous:
homozygous dominant:
homozygous recessive:
Be able to use a Punnett square to predict outcomes of genotypic and phenotypic ratios as well as percentages.
What is the law of independent assortment?
What is the law of segregation?
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A test cross is a cross between
an individual who's phenotype is dominant, (but genotype is unknown) and a homozygous recessive individual. Test crosses tell us the genotype of one parent
EX:
Plant with yellow seeds but unknown genotype = Y?
Plant with green seeds = yy
Heterozygous
Homozygous
If results are all yellow seeds: genotype of parent is____________
If results are half yellow and half green: genotype of parent is ____________
More Practice:
Biology Text Book p.172
Answer questions 1­4
p.169 Section 2 review
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Pedigree: a family history that shows how a trait is inherited over several generations.
• used in genetic counseling
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sex­linked trait
trait that is carried on the X chromosome and is recessive
XA Xa
XA X X
YX Y
A
A
A
XAXa
XaY
XA XA
Xa X X
YXY
A
a
A
XAXa
XAY
A = can see color
a = cannot see color
(no corresponding gene on the Y chromosome to "cover" it up)
• Females are "carriers"
• Usually males exhibit the trait
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Complex Patterns of Heredity
5 factors that influence patterns of heredity:
1. Polygenic inheritance
2. Incomplete dominance
3. Multiple alleles
4. Codominance
5. Environmental Influence 5
Polygenic Inheritance:
when one character is influenced by many genes.
Poly = Many
Examples: eyes color, hair color, autism, height, weight, skin color, asthma, ADHD, diabetes
Incomplete Dominance is when an individual displays a phenotype that is in between the two parents. Example: Red and White Snap Dragons
R=red
W= white
A red snapdragon is crossed with a white snapdragon. _____ x _____ RW=pink
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Multiple Alleles:
characters influences by three or more alleles
Example: blood types­­ A, B, AB, O
A and B are co­dominant both traits can be displayed at same time
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Environmental Factors
affect phenotypes
• pH affects hydrangea color • temperature affects fur color of arctic fox
summer
winter
• nutrition affects your height
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l
For traits we have studies so far, the dominant allele codes for something, but the recessive does not. In rabbits: B codes for "make brown pigment" but b codes for "I don't know how to make that" or "absence of brown pigment"
If a rabbit is a heterozygous (Bb), that rabbit has one set of instructions for “make brown” and one set of instructions for, “I don’t know how to make that,” with the result that the person ends up with brown fur color. Incomplete Dominance is when an individual displays a phenotype that is in between the two parents. Example: Red and White Snap Dragons
The dominant allele (R=red) codes for "make red pigment"
The recessive allele (r= white) codes for "make white pigment" Heterozygous Red snapdragon is crossed with a white snapdragon. _____ x _____ homozygous dominant :__________________
homozygous recessive :__________________
heterozygous:__________________
Heterozygous snapdragons have 2 sets of instructions: will turn out pink
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