Question

In humans, the disease galactosemia is inherited as a
**rare** autosomal recessive trait in a simple
Mendelian manner. A normal woman whose father had galactosemia
intends to marry a normal man whose grandfather had galactosemia.
What is the probability that their first child will have
galactosemia?

A. 1/2

B. 1/8

C. 1/16

D. 1/4

E. 0

Correct Answer: B. 1/8

Can you explain why?

Answer #1

**Correct answer : 1/8**

Galactosemia is an autosomal recessive disorder. These disorders are usually passed on by two carriers. Their health is rarely affected, but they have one mutated gene (recessive gene) and one normal gene (dominant gene) for the condition. Therefore, the probability of inheriting the disease from an affected parent is 50%, i.e., 1/2. Hence, in the question given above, the probability of the woman inheriting the affected allele from her father is 1/2 and the probability of the man inheriting the affected allele from his grandfather is 1/4

Hence, the probability of the child carrying the affected alleles = 1/2 x 1/4 = 1/8, i.e., there is a 1/8 probability that their first child will have galactosemia

The disease galactosemia is an autosomal recessive trait. A man
whose sister had galactosemia intends to start a family with a
woman whose great-grandfather was galactosemic. They are worried
about having a galactosemic child.
(assume no other relatives brought galactosemia-causing variants
into the family)
What is the probability of their first child
being affected with the condition?

. A man’s grandfather has galactosemia, a rare autosomal
recessive disease caused by the inability to process galactose,
leading to muscle, nerve, and kidney malfunction. The man married a
woman whose sister had galactosemia. The woman is now pregnant with
their first child.
b. What is the probability that this
child will have galactosemia?
c. If the first child does have
galactosemia, what is the probability that a second child will have
it?

Dentinogenesis imperfecta is a tooth disorder. The trait is
inherited as an autosomal dominant allele in humans. Assume that a
male with dentinogenesis imperfecta, whose mother had normal teeth,
married a woman with normal teeth. They had four children.
What is the probability that their first child will be a male
with dentinogenesis imperfecta?
What is the probability that three of their four children will
have the disease?

Two cousins marry and their first child has a rare autosomal
recessive trait conferring high musical ability. If they plan to
have 6 children, compute the expected chance that exactly four of
the six children will inherit this trait. Please show me how you
got it so I can understand. Also is the chance that they inherit
this trait referring to them being homozygous recessive or
heterozygous?

In humans, hemophilia depends on a recessive allele of a
sex-linked gene. Hemophilia is a disease in which the blood fails
to clot properly. A man whose father was hemophilic, but whose own
clotting time is normal, marries a normal woman with no record of
hemophilia in her ancestry. What is the chance of hemophilia in her
children?

Sickle cell anemia is an autosomal recessive disease. A man and
a woman are both heterozygous for the mutant gene. They have two
children and one has the disease. What are the chances their next
child will have the disease?
100%
75%
50%
25%

In humans, red-green color -blindness is a recessive X-linked
trait. A man with red-green colorblindnes marries a normal-vision
women whose father was color-blind. As the genitic counselor,
construct a Punnett square to determine the genotypic and
phenotypic possibilities of their children.

Attached earlobe and cystic fibrosis are both autosomal
recessive traits. A woman with attached earlobes, that is a carrier
of cystic fibrosis, marries a man that is genotypically normal for
cystic fibrosis and is a carrier of the attached earlobe trait.
What is the probability that they will have a child with
non-attached earlobes that is a carrier of cystic fibrosis?
A- 1/4
B-1/16
C-1/2
D-3/4

Albinism, a lack of pigmentation in humans, results from an
autosomal recessive gene. Two parents with normal pigmentation have
an albino child. What is the probability that their next two
children will have the same genotype?
a. 3/8
b. 11/16
c. 7/8
d. 13/16
e. 9/16

GENETICS
A trait is caused by a rare recessive autosomal allele with full
penetrance. Practically all individuals with the trait result from
matings between normal individuals. What would be the expected
concordance values for monozygotic and dizygotic twins?
A.
100% for both types of twins
B.
100% for monozygotic twins and 75% for dizygotic twins
C.
100% for monozygotic twins and 25% for dizygotic twins
D.
about 50% for both types of twins
E.
100% for monozygotic twins and 50%...

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