Empty Outline 9

Genetics

 

Use Chapter 14 as a Reference

 

Directions: 

 

Outline Grading Criteria

 

 

1.  Define the following terms:

           

            Gene

           

 

 

            Allele

 

 

 

Gonad

 

 

 

            Meiosis

 

 

 

            Gamete

 

 

 

            Diploid

 

           

 

            Haploid

 

 

 

            Zygote

 

 

 

            Sex Chromosome

 

 

 

            Autosome

 

 

 

            Homologous

 

 

 

            Homozygous

 

 

 

            Heterozygous

 

 

 

            Dominant

 

 

 

            Recessive

 

 

 

            Phenotype

 

 

 

            Genotype

 

 

            Character

 

 

 

 

            Trait 

 

 

 

            X-linked traits

 

 

 

 

  1. Distinguish between an individual’s “genotype” and their “phenotype”.  Give an example.

 

 

 

 

 

 

 

 

  1. Use the terms “dominant” and “recessive” in defining the following:

 

            Heterozygous:

 

 

 

 

            Homozygous:

 

 

  1. What is a “gene” as defined by a Mendelian geneticist?

 

 

 

 

  1. What is the relationship between a gene and an allele? Support your response with an example.

 

 

  1. State Mendel’s two laws in your own words. Include a simple diagram to illustrate each.

 

      Mendel’s 1st Law:       

 

 

 

 

 

      Mendel’s 2nd Law:      

 

 

 

To review and/or get a good introduction, see the student CD, chapter 14, activities.  They cover the monohybrid crosses, dihybrid crosses, and other concepts you need to know for this outline and this week.

 

 

 

7.  In Drosophila, black body color is recessive to gray body color. a geneticist had three pairs of flies with gray body color designated A, B, and C. The crosses she made and their results are tabulated below.

 

F1 Generation

Parental  Cross

Gray body

Black body

Ratio

A  x  B

109

0

100% Gray- bodied

A  x  C

80

28

2.86 : 1

B  x  C

76

0

100% Gray- bodied

     

      a.   What are the genotypes of A, B, and C? Justify your responses. Use Punnett squares where appropriate.

 

 

 

 

 

 

 

 

 

      b.   What are the expected phenotypic and genotypic ratios when flies A, B, and C are crossed with flies having black bodies?. Use Punnett squares where appropriate to justify your response.

 

 

 

 

 

 

 

8.  Below are the results of a few of Mendel’s F1 monohybrid crosses involving various characteristics in pea plants. Use these results to answer the questions that follow.

 

 

Character

Dominant

Trait

 

x

Recessive

Trait

F2 Generation

Dominant : Recessive

 

Ratio

Height

Tall

x

Dwarf

787  :  277

 

Pod color

Green

x

Yellow

428  :  152

 

Flower color

Purple

x

White

705  :  224

 

 

      a. Calculate the ratio of the F2 generation offspring for each cross. Record your responses in the table above.

 

 

 

      b.   Discuss how the results of these crosses led Mendel to his first law, the law of segregation.

 

 

 

 

 

9.  Below are the results from Mendel’s dihybrid cross between true-breeding (i.e. homozygous) parent plants differing in two traits, flower color and height.

     

Generation

Phenotypes

Parents

(Purple-flowered, tall)   x   (white-flowered, dwarf)

  

F1

100%  purple-flowered, tall

 

F2

630 purple-flowered, tall

 

216 purple-flowered, dwarf

 

202 white-flowered, tall

 

 64  white-flowered, dwarf

 

      a.   Calculate the phenotypic ratio for the F2.

            Compare the expected phenotypic ratio for the F2 with that obtained by Mendel in the table above. Explain why they are different.

 

 

 

 

 

 

 

b.      Discuss how the results of these crosses led Mendel to his second law, the law of independent assortment.

 

 

 

 

 

 

 

 

 

 

 

 

      c.   What would be the expected phenotypic ratios for the F1 and the F2 if pairs of alleles segregated together (i.e. dependent assortment), rather than assorting independently. Justify your response.

 

 

 

 

10.  Which of Mendel’s Laws are best illustrated by the events that occur in the process of meiosis?

       

 

 

 

 

 

 

11.  Do laws prohibiting marriages between brothers and sisters make biological sense? Explain in terms of recessive traits.

 

 

 

 

 

12.  How could you determine if an individual really is pure-breeding for all traits?

 

 

 

 

 

 

13.  Complete dominance and incomplete dominance differ in the amount of variation seen in the offspring.

       

        a.   How many genotypes are possible with complete dominance involving two alleles? List them.

             

 

 

 

 

 

              How many phenotypes are possible? List them.

 

 

 

       

 

        b.   How many genotypes are possible with incomplete dominance involving two alleles?  List them.

 

 

 

 

 

              How many phenotypes are possible? List them.

 

 

 

       

14. Why is a recessive sex-linked allele always expressed in human males, but not always expressed in females?

 

 

 

 

 

15.  Make a diagram of an unduplicated chromosome containing two different genes, gene A and gene B. Use this diagram to explain gene locus and gene linkage.

 

 

 

 

        b.   Why does gene linkage interfere with independent assortment?

 

 

 

c.       Suppose the genotype of an organism is AaBb. If the genes A and B are linked on one chromosome (as in part a, above), and their recessive alleles, a and b, are on the other homologue, how many different genetic types of gametes would be produced in the absence of crossover? List them. Note: You should be able makes a diagram of meiosis to show how these gametes would be produced.