When doing a test cross, an organism with unknown genotype is mated with one…
That is homozygous recessive for a trait
What is a carrier?
Someone heterozygous for a disease that shows no symptoms but CAN pass it on to offpsring.
John is blind, which is recessive. His parents are NOT blind. What are their
genotypes? John’s?
Parents: Heterozygous (for example: Bb)John: homozygous recessive (bb)
Why do men get sex linked genes more often than women?
Men only need to have one recessive allele (on their one X gene) in order to get the condition. Women have to inherit 2, one on each X.
What is heterozygous?
Two different alleles for the same trait, one dominant and one recessive, written Bb.
What are the 3 types of fetal screening?Which is the LEAST invasive?
Ultrasound, CVS, amniocentesisUltrasound
Brown eyes are dominant (B) to blue (b). White hair (W) is dominant to gray (w).
What’s the genotype of blue eyes and grey hair?
bbww
Brown eyes are dominant (B) to blue (b). White hair (W) is dominant to gray (w).
genotype. Bbww =
Brown eyes, gray hair
Purple flowers are dominant to white. Cross 2 heterozygous flowers. What’s the probability of a
white flower?
1/4
Purple flowers are dominant to white. Cross a heterozygous with a white. What’s the probability of
a white flower?
1/2
Purple flowers are dominant to white. Cross two homozygous purple flowers. What’s the probability
of a white flower?
0
Brown eyes are dominant. A blue eyed child has brown eyed parents. What are their genotypes?
Bb and Bb
Brown eyes are dominant to blue. Two heterozygous parents have a child. What is the probability that the child will have
brown eyes?
3/4
Tall plants are dominant to short. A homozygous tall and short plant are crossed. What is the expected
phenotypic ratio
4/4 tall
Purple flowers are dominant to white. Cross a heterozygous with a white. If there are 400 babies,
how many will be white?
200
Incomplete dominance: Red (RR), Pink (Rr), white (rr). Cross a red and white and show your phenotypic
ratio.
4/4 pink
Incomplete dominance: Red (RR), Pink (Rr), white (rr). Cross two pinks. How many offspring will be
red?
¼ red
Incomplete dominance: Red (RR), Pink (Rr), white (rr). Cross 2 pinks and show the phenotypic ratio
1 red: 2 pink: 1 white
Incomplete dominance: Red (RR), Pink (Rr), white (rr). Cross 2 pinks and show the genotypic ratio
1 RR: 2 Rr: 1 rr
A man has heterozygous B blood, a woman has heterozygous A blood. What can their children have?
A, B, AB, or O
Mom has type A blood. Baby has type O. Dad 1 has type AB and Dad 2 has type A. Who is the baby
daddy?
Dad 2
A person with type AB can receive what blood types?
Any, AB is the universal receiver
O is the universal donor.
Color blindness is sex-linked. Cross a normal man with a carrier woman. What are the chances a son
will be blind?
1/2
Color blindness is sex-linked. Cross a normal man with a carrier woman. What are the chances a daughter will
be blind?
0
Color blindness is sex-linked. Cross a blind man and a carrier. What are the chances a daughter will be a
carrier?
1/2
Color blindness is sex-linked. Cross a blind man and a blind woman. What are the chances a daughter
will be blind?
100%
Long (L) is dom to short (l) and yellow (Y) is dom to green (y). Cross a homozygous long heterozygous
yellow with a short ?heterozygous yellow bird. How many are LlYy?
8/16
Dark (D) is dom to light and Brown (B) is dom to blue. Cross two people heterozygous for BOTH traits.
What is the prob of a light brown eyed child?
3/16
Dark (D) is dom to light and Brown (B) is dom to blue. Cross a heterozygous dark heterozygous brown with a light heterozygous brown. Show phenotypic
ratios.
6/16 dark brown, 6/16 light brown, 2/16 dark blue, 2/16 light blue
A filled in circle or square means
Someone has the condition or diseaseGenotype is homozygous recessive (aa)
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