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1 of 28
Do now:
1) Put these in order from which is the largest to the smallest:
gene
nucleus
chromosome
cell
DNA
Friday, April 21, 2023
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Do now:
1) Put these in order from which is the largest to the smallest:
cell
nucleus
chromosome
gene
DNA
Friday, April 21, 2023
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1) Explain what is meant by dominant and recessive
2) Explain what an allele is
2) Use a Punnett Square
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X
X
X
Y
Male
Female
XX
XY
XX
XY
Copy!
Tongue rolling
How many people in the class could roll their tongues?
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R
R
r
r
Male
Female
RR
r r
Rr
Rr
Roller gene (R) is dominantNon-roller gene (r) is
recessive
Probabilities
Homozygous dominant and
recessive
Heterozygous
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B
B
b
b
Male
Female
BB
bb
Bb
Bb
Brown eyes (B) are dominant
Blue eyes are recessive (b)
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An allele is just a type of gene e.g. B=Brown eyes, b = blue eyes
The allele which will always be expressed is called the Dominant allele.
The allele which may be hidden is called the Recessive allele.
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In mice, pointed ears (E) are
dominant over round ears (e)
Draw the Punnett square for offspring of a “pure-breed” male with pointed ears (EE) and a female with round ears (ee).
What is the probability the offspring has round ears?
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In mice, pointed ears (E) are
dominant over round ears (e)
Draw the Punnett square for offspring of a “cross-breed” male with pointed ears (Ee) and a female with round ears (ee).
What is the probability the offspring has round ears?
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Hypertrichosis
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