Download mendelian genetics problems

Honors Biology
Unit 12 - Genetics
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MENDELIAN GENETICS PROBLEMS
1.
In squash, white fruit color is dominant, yellow is recessive. A squash plant that is
homozygous for white is crossed with a homozygous yellow fruited plant. Predict the
appearance of:
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The F1 generation
The F2 generation
The offspring of a cross between an F1 individual and a homozygous yellow
individual
In garden peas, tall vine is dominant and short vine is recessive.
2. If a homozygous tall plant is crossed with a homozygous short plant, what genotypes are
possible in the F1 generation?
3.
What will be the genotypic and phenotypic ratios of the F2 generation?
In dogs, wire hair is dominant and smooth hair is recessive. A dog breeder wants to
determine whether a male dog with wire hair will produce only offspring with wire hair.
4. How can the breeder determine whether the dog is homozygous dominant or
heterozygous for the wire hair?
5.
Many sheep are black, but some are also white. How would you determine if the white is
dominant or recessive?
6. Brown eyes (B) are dominant to blue eyes (b). A man heterozygous for brown eyes marries
a woman heterozygous for brown eyes. What are the chances that their first child will
have blue eyes?
DIHYIBRID and TRIHYBRID
7. What is the genotype of the children if a man homozygous recessive for attached
earlobes and homozygous dominant for widow’s peak reproduces with a woman who is
homozygous dominant for unattached earlobes and homozygous recessive for a straight
hairline?
8.
If an individual from this cross reproduces with another of the same genotype, what are
the chances that they will have a child with a straight hairline and attached earlobes?
In dragons, blue scales are dominant over red scales, and sharp teeth are dominant over flat
teeth.
9. If one dragon that is heterozygous for both traits has children with another dragon that
is heterozygous for both traits, what is the probability that their child will also be
heterozygous for both traits?
10. A pea plant heterozygous for being tall, having blue flowers, and round seeds, is breed
with a pea plant that is short, has white flowers, and wrinkled seeds. What is the
probability that the resulting plants will be short, have wrinkled seeds and will be
heterozygous for having blue flowers?
11. Same traits as previous problem. Plants heterozygous for all three traits breed together.
What is the probability that their resulting progeny will be tall, blue, and have round
seeds?
12. What is the genotypic ratio of this cross?
DdHh x ddhh
INCOMPLETE DOMINANCE and CODOMINANCE
In snapdragons, flowers can be red (homozygous RR), white (homozygous R’R’), or pink
(heterozygous RR’).
13. When a red flower is crossed with a white flower, what genotypes and phenotypes of
offspring could be obtained?
14. If one of the offspring above were crossed with a white flower, what genotypes and
phenotypes could be obtained?
In certain cattle, hair color can be red (homozygous RR), white (homozygous R’R’) or roan (a
mixture of red and white hairs, heterozygous RR’).
15. When a red bull is mated to a white cow, what genotypes and phenotypes of offspring
could be obtained?
16. If one of the offspring in (a) were mated to a white cow, what genotypes and phenotypes
of offspring could be produced? In what proportion?
In mythical dragons, there is gene that produces a protein essential to their scales. The
alleles for this gene are codominant. The P allele produces scales that are poisonous. The R
allele produces scales that are razor-sharp.
17. Explain how a parent with sharp scales and a parent with poisonous scales could have
children more deadly than either parent.
SEX-LINKED
Colorblindess is a sex-linked recessive trait, carried on the X chromosome
18. If a man and a woman, both with normal vision, marry and have a colorblind son, draw the
Punnett square that illustrates this.
19. If the man dies and the woman from the question above remarries to a colorblind man,
draw a Punnett square showing the type(s) of children that could be expected from this
marriage. How many/what percentage of each type of child could be expected?
20. Jane and Michael are both colorblind. What percentage of their children will be
colorblind?
Hemophelia is a sex-linked, recessive trait.
21. Princess Eugenie, who was a carrier for hemophilia, married her cousin Prince Albert
who was a hemophiliac. Draw a Punnett square to predict their offspring.
22. What percentage of their sons will be hemophiliacs?
23. What percentage of their daughters will be hemophiliacs?
24. What percentage of ALL of their children will be hemophiliacs?
25. What percentage of their children will be female carriers who do not show the trait?
26. A man named Charles has an unusual mutation on his X chromosome that causes his skin
to be green. The chances of Charles or his children ever meeting anyone with the same
genetic mutation is virtually zero. Charles meets a woman name Chloe who is able to
overlook his green skin (because she is colorblind) and they have children.
a. Will any of their children be green? Why or why not?
b. Will any of their children be carriers for the green skin genes? What will be the
gender of these children?
c. Will any of the grandchildren be green? Explain why or why not.
MULTIPLE ALLELES
1. If a woman with genotype IAIA marries a man with phenotype AB, complete the
Punnett square to predict their offspring.
2. A young man, whose blood type is O claims to be the missing song of a wealthy
businessman. The businessman’s blood is AB. Could the young man have been his
son? Why or why not?
3. A woman with type A blood gives birth to a child whose blood is type B. A man
with type O blood and a man with type AB blood are both being charged in a
paternity suit. Which man is innocent? How do you know? You can’t prove that
either man is the father, but you can prove that one man is definitely not the
father.
4.
In stick figures, head shape is controlled by the following multiple alleles:
a.
C = circle head (dominant to all others)
b.
S = square head (recessive only to C)
c.
T = triangle head (dominant only to N)
d.
N = No head (recessive to all others)
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Draw
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the stick figures with the following genotypes:
CS
--NN
TN
-- ST
TT
-- CC
POLYGENETIC INHERITANCE
1.
In humans, hair color is controlled by two interacting genes. The same pigment,
melanin, is present in both brown-haired and blonde-haired people, but brown hair
has much more of it. Brown hair (B) is dominant to blonde (b). Whether any
melanin can by synthesized depends on another gene. The dominant form of that
gene (M) allows melanin synthesis; the recessive form (m) prevents melanin
synthesis. Homozygous recessive (mm) are albino. What will be the expected
phenotypic ratios in the children of the following parents? (Hint: try to do this
without creating a Punnett Sqaure!!!)
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BBMM x BbMm
BbMm x BbMm
BbMm x bbmm
LINKED GENES