UGen - X Linked Recessive

Duchenne muscular dystrophy is a recessive X-linked disorder.

According to the Punnett square, what percentage of offspring will have the disorder?

• 0%

• 25%

• 50%

• 100%

Answer explanation

Duchenne muscular dystrophy is X-linked recessive. If a carrier mother (X^D X^d) has a son (Y), there's a 25% chance he inherits the X^d (affected) and a 75% chance he inherits X^D (unaffected). Thus, 25% of sons will have the disorder.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Which genotype do females have?

• XX

• XY

• AA

• Aa

Answer explanation

Females typically have two X chromosomes, represented as the genotype XX. This distinguishes them from males, who have one X and one Y chromosome (XY). The other options (AA, Aa) do not represent sex chromosomes.

If hemophilia is an X-linked recessive disorder, what genotype would a female with hemophilia have?

• XH XH

• XH Xh

• Xh Xh

• Xh Y

Answer explanation

A female with hemophilia must have two copies of the recessive allele, represented as Xh Xh. The XH XH genotype would indicate no hemophilia, and XH Xh would indicate a carrier, not affected.

Tags

NGSS.HS-LS3-1

In a sex-linked dominant trait, which of the following would NOT have the trait?

• XH Xh

• Xh Xh

• XH Y

• XH XH

Answer explanation

In a sex-linked dominant trait, XH represents the dominant allele. Xh Xh individuals have two recessive alleles and would not express the trait, while all other combinations (XH Xh, XH Y, XH XH) would express it.

Tags

NGSS.HS-LS3-1

What genotype should be placed in the box with a question mark?

• X^HX^h

• X^HX^H

• X^hY

• X^HY

Answer explanation

The correct genotype is X^HY because it represents a male with the dominant allele for a trait, while the other options either represent females or do not match the required male genotype.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Fill in the rest of this Punnett Square for the X-linked trait.

c

d

g

h

a

Xb Y

XB Y

Xb Xb

Xb

XB Xb

XB XB

XB

Y

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

X-linked recessive genetic disorders are more common in ​ (a)   because they have ​ (b)  

• males

• one X chromosome

• females

• two X chromosomes

Answer explanation

X-linked recessive disorders are more common in males because they have one X chromosome. If a male inherits a recessive allele on his X chromosome, he will express the disorder, while females with two X chromosomes may be carriers.

Hemophilia is a recessive x-linked disorder.
Which genotype represents a female who is a carrier for hemophilia?

• X^HX^h

• X^hX^h

• X^HX^H

• X^hY

Answer explanation

A female carrier for hemophilia has one normal X chromosome (X^H) and one affected X chromosome (X^h). Thus, the correct genotype is X^H X^h, indicating she carries the hemophilia allele without expressing the disorder.

Tags

NGSS.HS-LS3-1

Hemophilia also known as bleeder's disease is an X-linked trait. A mother who is heterozygous for hemophilia married a man without hemophilia. Examine the cross and identify the offspring with normal phenotype. Select all that apply.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Match the following

• normal vision male

• XⁿY

• normal vision female carrier

• X^NXⁿ

• colorblind female

• XⁿXⁿ

• normal vision female

• X^NX^N

• colorblind male

• X^NY

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2