Probability Practice

Egypt (35 XX) is a carrier of the sickle cell anemia trait (SCA). Her boyfriend, Common (XY), is too. What is the likelihood the two will have six of eight children with SCA? Express your answer as a percentage with 3 significant digits. Be sure to add the percent sign.

Harrison (XY) has hemophilia a, an X-linked recessive disorder, but his father, sister, and brother do not. What must the genotypes be for the parents? 

• Mom- Aa

  Dad - AA

• Mom- aa

  Dad- AA

• Mom- X^AX^a

  Dad- X^AY

• Mom- X^aX^a

  Dad- X^AY

Mitchell (XY) has DMD. The mother of his two children is a carrier of the DMD trait.  

A) What is the likelihood their first three children will be carriers of the DMD trait? 

B) What is the likelihood they will have four of seven children who do not have DMD? 

Express your answer as a percentage with three significant digits.

• A) 12.5%

  B) 0.391%

• A) 1.56%

  B) 27.3%

• A) 42.2%

  B) 27.3%

Divine (XX) has XLH. The father of her children, Bob, does too. Their son, Bob Jr. does not have XLH. Use the letter H to represent the genotype.

a.     What are the genotypes of Divine and Bob?

• Divine- X^HX^H

• Bob- X^hY

• Divine- X^HX^h

• Bob- X^HY

Divine (XX) has XLH. The father of her children, Bob, does too. Their son, Bob Jr. does not have XLH. What is the probability Divine and Bob will have a child with the same genotype as Bob Jr.?

• 0%

• 25%

• 50%

• 75%

• 100%

Yvonne (XX) has Huntington’s disease; she has one normal copy of the HTT gene and one mutated copy of it. She would like to know the chance she and her partner, Isaac (XY), will have 1 of 5 children with Huntington’s disease. Isaac does not have Huntington’s disease. Express your answer as a percentage with three significant digits.

Lauren (XX) is a carrier of hemophilia. Her partner, Mike (XY), does not have hemophilia. What is the probability that their first four children have the same phenotype as Lauren? Express your answer as a percentage with three significant digits.

• 0.625%

• 25.0%

• 0.391%

• 6.25%

Emma (XX) does not have cystic fibrosis, but she is a carrier. Her husband, Ethan (XY), has cystic fibrosis. What is the chance that their first child will be a carrier of the cystic fibrosis gene but not have the disease? Express your answer as a percentage with three significant digits.

Jack (XY) has Marfan syndrome. His wife, Jill (XX), does not have the disorder. What is the probability that their first child will inherit the disorder from Jack? Express your answer as a percentage.

• 0%

• 25%

• 50%

• 75%

• 100%

Jack (XY) has Marfan syndrome. His genotype is _.

• Hh

• X^hY

• X^hY^h

• hh