C.14/15 - Genetics

Question 1

True Breeding Character/Trait

Answer 1

Plants that produce offspring of the same variety when they self-pollinate

Question 2

P, F1, and F2 Generations

Answer 2

P - The true-breeding parents
F1 - The hybrid offspring of the P generation
F2 - When F1 individuals self-pollinate or cross- pollinate with other F1 hybrids

Question 3

Dominant and Recessive Alleles

Answer 3

If two alleles at a locus differ, then one (the dominant allele) determines the organism’s appearance, and other (the recessive allele) has no noticeable effect

Question 4

Genotype and Phenotype

Answer 4

Different effects of dominant and recessive alleles do not always reveal an organisms genetic composition. Must distinguish between an organism’s phenotype, or physical appearance, and its genotype, or genetic makeup.

Question 5

Testcross

Answer 5

Breeding the mystery individual with a homozygous recessive individual. If any offspring display the recessive phenotype, the mystery parent must be heterozygous

Question 6

Law of Segregation

Answer 6

Two alleles for a heritable character segregate during gamete formation and end up in different gametes, so an egg or a sperm gets only one of two alleles. This corresponds to distribution of homologous chromosomes to different gametes in meiosis
Accounts for 3:1 ratio observed in F2 generation.

Question 7

Law of Independent Assortment

Answer 7

Alleles segregate independently of each other during gamete formation, only applies to genes on different, non-homologous chromosomes (Genes located near each other on the same chromosome tend to be inherited together)

Question 8

Complete Dominance

Answer 8

Occurs when phenotypes of the heterozygote and dominant homozygote are identical (Purple/White Pea Plant Flowers)

Question 9

Incomplete Dominance

Answer 9

The phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties (White/Red Roses make Pink)

Question 10

Codominance

Answer 10

Two dominant alleles affect the phenotype in separate, distinguishable ways (White and Black Cows make Cows with white and black patches)

Question 11

Pleiotropy

Answer 11

Genes that have multiple phenotypic effects. Responsible for the multiple symptoms of certain hereditary diseases, such as cystic fibrosis and sickle-cell

Question 12

Epistasis

Answer 12

A gene at one locus alters the phenotypic expression of a gene at a second locus. For example, in Labrador retrievers and many other mammals, coat color depends on two genes; One gene determines pigment colour, another gene dictates whether pigment will be deposited in hair