Genetics Worksheet

Associate Program Material

Genetics Worksheet

Review the images below and answer the follow-up questions.

Questions:

1. According to the pedigree, is cystic fibrosis inherited as a dominant or as a recessive trait? Explain how you made your conclusion using evidence from the pedigree and the principles of genetics.

Cystic Fibrosis is a recessive trait. You have to inherit two copies of the allele to have cystic fibrosis. If you have just one of these alleles you could be a carrier of cystic fibrosis, but have absolutely no symptoms. If two carriers of this allele have a child then there could be a one in four chance that child would have cystic fibrosis. I made my conclusion by using the evidence to see that from the pedigree and the principles of genetics that it had skipped generations. In this pedigree the parents don’t have cystic fibrosis but the child does. Both parents are heterozygous because the cystic fibrosis allele is recessive, but the children of these parents can inherit the allele.

2. What would a Punnett square that shows how the son in generation IV (marked with an A) inherited cystic fibrosis look like?

A- Not a carrier of cystic fibrosis a- Carrier of cystic fibrosis

| | A | a |
| A | AA | Aa |
| a | Aa | aa |

Questions:

1. According to the pedigree, is Huntington’s disease inherited as a dominant or as a recessive trait? Explain how you made your conclusion using evidence from the pedigree and the principles of genetics.

Huntington’s disease (HD) is inherited as a dominant trait. An individual inherits HD (Huntington’s disease) when they inherit and expanded HD allele from one parent. The risk of having a child that will get HD depends on the size of the HD allele in the parent. If one parent has an allele with 40 or more repeats, all their children will have a 50% chance of inheriting the allele and getting Huntington’s disease. I made my conclusion by using the evidence to see that from the pedigree and the principles of genetics that from the male in the first generation it was continued to be passed down but not to everyone but that there is a 50% chance of them inheriting Huntington’s disease.

2. What would a Punnett square that shows how the first daughter in generation II (marked with a B) did not inherit Huntington’s disease look like?

B- Not a carrier for Huntington’s disease b- Carrier for Huntington’s disease

| | B | b |
| b | Bb | bb |
| b | Bb | bb |

3. What is the role of chromosomes in the inheritance of genetic traits, such as cystic fibrosis and Huntington’s disease?

The role of chromosomes in the inheritance of genetic traits is to carry the genetic traits. Heredity is the passing of DNA from the chromosomes of one generation to the chromosome of the next. Chromosomes in your body are in pairs. One chromosome of each pair came from your mother and one from your father. There are many alleles in each chromosome. Different alleles determine different traits. For each allele there can be many different traits (Simon, Reee, & Dickey).

References
Simon, E.J., Reece, J.B., & Dickey, J.L. (2010). Campbell Essential Biology with Physiology. (3rd. Ed.). : Pearson Education, INC.

References: Simon, E.J., Reece, J.B., & Dickey, J.L. (2010). Campbell Essential Biology with Physiology. (3rd. Ed.). : Pearson Education, INC.