Download Study Guide_Genetics Answers

Genetics Practice Problems Answers:
1. In humans, brown eyes …
a. What is the man’s genotype? Bb
b. If blue is recessive, what must the woman’s genotype be? bb
c. If that is her genotype, what kind(s) of gametes (eggs) can she
produce? Only gametes with the recessive, blue gene (b)
d. What kind(s) of gametes can the man produce? Gametes with
the dominant brown gene (B) and with the recessive blue gene
(b)
e. What are the genotypes of the children? Bb or bb
B
b
Bb
b
Bb
b
bb
bb
2. In dogs…
a. Explain how the breeder can perform a test cross to determine
the genotype of the dog. A test cross can be performed by
breeding her dog, which may be DD or Dd with a deaf dog (dd)
b. How will the owner know if it is alright to breed the dog? If any
of the offspring from the test-cross are deaf, then the owner
should not breed her dog further. She can continue breeding her
dog if all of the puppies have normal hearing.
c. What may be the ethical complications of performing test
crosses on animals? This may create ethical issues because
there may be a chance of producing more deaf dogs, which are
undesirable. Even if the offspring from the test cross are not
deaf, those dogs are carriers of deafness.
3. Yellow is dominant…
yr
YyRr X yyrr
YR
Yr
YyRr
Yyrr
yR
yyRr
yr
yyrr
a. What are the possible phenotypes and genotypes of the
offspring?
Genotypes: 25% YyRr, 25% Yyrr, 25% yyRr, 25% yyrr
Phenotypes: 25% Yellow round, 25% yellow wrinkled, 25%
green round, 25% green wrinkled
b. What is the probability of producing a plant that has green and
round seeds? 25% chance
4. In areas of the southeastern …
LlNn X LlNn
LN
Ln
lN
LN
LLNN
LLNn
LlNN
Ln
LLNn
LLnn
LlNn
lN
LlNN
LlNn
llNN
ln
LlNn
Llnn
llNn
ln
LlNn
Llnn
llNn
llnn
a. What are the genotypes of the parents? LlNn (both)
b. What gametes can be produced by each parent? LN, Ln, lN or
ln
c. What is the probability of producing a Palmetto bug with bent
wings and short antennae? (llnn, 1/16 chance)
5. In northeast Kansas …
a. What is the probability of having a Red individual if a blue cat is
bred with a purple cat? No chance
B
BB x BR
B
B
BB
BB
R
BR
BR
6. A certain disease ...
a. Draw a Punnett square of the possible offspring. See punnett
square below
b. What is the chance they will have an unaffected child? 50%
chance (Dd)
d
D
Dd
d
dd
d
Dd
dd
7. In blood typing…
a. What would be the genotypes of the children by a homozygous
Type A mother and a father with Type AB blood?
iA
iA
iA iA
iA
iA iA
iB
iA iB
iA iB
8. Colorblindness …
a. Draw a Punnett square of the possible offspring.
Xc
X
X Xc
Xc
Xc Xc
Y
XY
Xc Y
b. What is the chance that they will have an affected child? 50 %
chance (Xc Xc = colorblind girl, Xc Y = colorblind boy.)
c. Could any of their daughters be affected? Yes
9. Albinism is an autosomal recessive disorder. This means that people
who are homozygous recessive (aa) have albinism. Below is the
pedigree of a family.
a. Which family members are homozygous recessive (aa)?
b. Which family members must be heterozygous (Aa)?
Aa
Aa
Aa
Aa
aa
aa
aa
aa