Name:______

Per:______Teacher:______

Biology- Unit #6 – Basic Genetics

Essential Skills

  • Be able to show the expected phenotype and genotype ratios for any single trait Punnett Square cross.
  • Recognize the terms genotype, phenotype, dominant, recessive, heterozygous and homozygous.

Study Guide

1. Who was Gregor Mendel? What were his contributions to our understanding of heredity?

2. Using the height of plant (Tall & Short). Explain how Mendel obtained his P generation, the results of the F1 generation and the results of the F2 generation.

3. How did Mendel’s results with pea plants show that alleles are either dominant or recessive? Use examples to explain.

4. Explain how the following terms relate to each other:

  1. DNA – Chromosome
  1. Gene – Chromosome
  1. Gene – Trait
  1. Trait – Allele

5. What is the Law of Segregation? How is this related to the Law of Independent Assortment?

6. Explain the purpose of Meiosis. How many cells? Types of cells? Chromosome Number?

7. Draw a picture of Crossing-over. Show the alleles on different chromatids and the new combinations of genes produced.

8. Compare and contrast the following sets of terms:

* Dominant vs. Recessive –

* Genotype vs. Phenotype –

* Homozygous vs. Heterozygous –

* Purebred vs. Hybrid -

  1. How does genotype affect phenotype? Use the terms dominant, recessive, homozygous and heterozygous.

10. If short tails are dominant to long tails, what are the phenotypic and genotypic ratios of a cross between a dog with a long tail and a dog with a short tail (who had a parent with a long tail)?

11. If you had a long tailed dog and did not know the phenotypes of its parents, how could you conclusively determine the genotype of your dog? Explain using examples of a Test Cross.

12. Complete the following table that summarizes the 4 basic genetic crosses: (B=black; b =brown)

Word Cross / Genotype Cross / Offspring Genotype Ratio / Offspring Phenotype Ratio
BB x bb
Homozygous Dominant x Heterozygous
1 BB: 2 Bb: 1 bb
2 Black : 2 Brown

13. How are Incomplete Dominance and Codominance similar? How are they different from each other? Give examples of each type of inheritance.

14. Differentiate between a multiple allele trait versus a trait that was determined by polygenic inheritance. Give examples of each type of inheritance.

15. Show the expected genotype and phenotype ratios of a cross between a man with type A blood and a woman with type B blood (both the man and woman had parents with type O blood).

16. What is the difference between Autosomes and Sex Chromosomes? What sex chromosomes determine male? Female? Why do sex-linked traits affect males more than females?

17. Show the expected genotype and phenotype ratios of a cross between a man who is colorblind and a woman who has normal vision (but her father was colorblind).

18. Pedigrees:

19. Summarize the following Genetic Disorders:

Disorder / Description / Pattern of Inheritance
Hemophilia
Sickle cell anemia
Cystic Fibrosis
Huntington’s disease
Tay-Sachs disease
(PKU) Phenylketonuria

20. Summarize the following types of mutations:

I. Chromosomal –

a. deletion –

b. nondisjunction –

II. Gene Mutation –

a. point mutation –

b. frame-shift mutation