Name______Period ______

Albinism

People with albinism have little or no pigment in their eyes, skin, or hair. They have inherited altered genes that do not make the usual amounts of a pigment called melanin. One person in 17,000 in the U.S.A. has some type of albinism. Albinism affects people from all races. Most children with albinism are born to parents who have normal hair and eye color for their ethnic backgrounds. A common myth is that people or animals with albinism have red eyes. In fact there are different types of albinism and the amount of pigment in the eyes varies. Although some individuals with albinism have reddish or violet eyes, most have blue eyes. Albinism is a “recessive trait”. This means that a person has to inherit two copies of this trait- one allele from each parent- to possess the traits that are characteristic of albinism. If a person only inherits one allele for albinism, they will have normal skin pigmentation, however they are said to be carriers of this trait. This type of inheritance is called “autosomal recessive” inheritance.

______

In humans, normal skin pigmentation (N) is dominant over albinism (n).

Someone with albinism would have the genotype ______

Someone with normal skin pigmentation would have either the genotype ______or _____.

  1. Cross a homozygous dominant person with a person that is heterozygous.

A.Parent Genotypes ______x ______

C. What chance do these parents have to have children with albinism? ______

D. What chance do these parents have to have children with normal pigmentation? ______

  1. Cross a person with albinism with a person that is heterozygous.

A. Parent Genotypes ______x ______

B.

C. What chance do these parents have to have children with albinism? ______

D. What chance do these parents have to have children with normal pigmentation? ______

  1. Cross a man that is homozygous recessive with a woman that is homozygous dominant.

A. Parent Genotypes ______x ______

B.

C. What chance do these parents have to have children with albinism? ______

D. What chance do these parents have to have children with normal pigmentation? ______

  1. Cross a man that is homozygous recessive with a woman that is homozygous recessive.

A. Parent Genotypes ______x ______

B.

C. What chance do these parents have to have children with albinism? ______

D. What chance do these parents have to have children with normal pigmentation? ______

  1. Cross a man that is a carrier for albinism with a woman that is a carrier for albinism.

A. Parent Genotypes ______x ______

B.

C. What chance do these parents have to have children with albinism? ______

D. What chance do these parents have to have children with normal pigmentation? ______

Answer the following questions, using the information contained in your Punnett Squares.

  1. With recessive traits like albinism, a person has to inherit ______alleles to inherit the disease.
  1. If a person that has normal skin pigmentation (NN) has children, they have a ______chance of having children with albinism no matter who they marry.
  1. August and Henry, both with normal skin pigmentation, have offspring that are born with albinism. August and Henry must be carriersof albinism and both of their genotypes must be ______.
  1. If two people, both with normal skin pigmentation, but who are carriers of albinism (Nn) have children, they have a ______chance of having children with albinism.
  1. If a person with normal skin pigmentation (Nn) has offspring with a person that has albinism, they have a ______chance of having offspring with normal skin pigmentation and a ______chance of having offspring with albinism.