Reading 16

Question 1

What type of organism did Mendel use in his heredity experiments? What are some advantages of Mendel’s choice of model?

Answer 1

-pea plants
-2 different alleles for several traits, grows quickly

Question 2

How many alleles are included in the genotype at a single locus?

Answer 2

-2

Question 3

What is meant by ‘genotype’?

Answer 3

-Set of alleles an organism possesses

Question 4

What is the difference between a genotype that is heterozygous vs. one that is homozygous?

Answer 4

-heterozygous: 2 different alleles at a locus
-homozygous: same alleles at a locus

Question 5

What is a monohybrid cross?

Answer 5

-crosses between parents that differ in a single characteristic

Question 6

Mendel derived two major conclusions from his work with monohybrid crosses in pea plants (Pisum savitum) (also see question #1 above). One of these is referred to as “Mendel’s First Law”. What are these conclusions, and the significance of each in the context of “heritable material”?

Answer 6

-2 conclusions: principle of segregation and concept of dominance
-principle of segregation: each individual diploid organism possesses 2 alleles for any characteristic, one inherited from the maternal parent and one from the paternal parent
-concept of dominance: when 2 different alleles are present in a genotype, only the trait encoded by the dominant allele is observed in the phenotype

Question 7

What is a dihybrid cross?

Answer 7

-crossing parents that differ in 2 characteristics

Question 8

A third major conclusion was derived from Mendel’s work with dihybrid crosses (“Mendel’s Second Law”). What is described by this principle?

Answer 8

-principle of independent assortment: alleles at different loci separate independently of one another

Question 9

What is dominance?

Answer 9

-the trait encoded by only one allele which is present in the phenotype

Question 10

How is complete dominance distinguished from incomplete dominance?

Answer 10

-complete dominance: only one allele trait is shown (dominant)
-incomplete dominance : Both traits are shown intermediately

Question 11

True or False: The allelic interaction describes interactions between the products of genes at the same locus (alleles).

Answer 11

-True

Question 12

True or False: Dominance is an allelic interaction.

Answer 12

-True