Exam 2 - Chapter 8: Variation of Phenotypes

Question 1

What is a dihybrid cross? What is the genotypic ration produced?

Answer 1

When two individuals with two heterozygous traits reproduce; 9:3:3:1

Question 2

What is Mendel’s law of independent assortment?

Answer 2

Pairs of chromosomes segregate independently during meiosis

Question 3

What is a complex trait?

Answer 3

A phenotype controlled by multiple genes and/or the environment

Question 4

What is a fully dominant allele?

Answer 4

When an individual expresses dominant trait and no degree of recessive trait if they have a dominant allele

Question 5

What is incomplete/intermediate dominance?

Answer 5

A heterozygous individual experiences an intermediate of phenotypes

Question 6

What is codominance?

Answer 6

A heterozygous individual expresses both alleles equally

Question 7

What is the ABO locus?

Answer 7

A gene of chromosome 9 that makes glycosyl transferase which modifies H-antigens on red blood cells

Question 8

How do alleles A and B of the ABO locus compare in dominance?

Answer 8

They are codominant

Question 9

What is an allele series?

Answer 9

dominance varies between alleles in a gradient

Question 10

What is pleiotropy?

Answer 10

one gene produced multiple effects in an organism

Question 11

How do mutations differ from alleles?

Answer 11

Associated with disease, immediate and low frequency

Question 12

What is a polymorphism?

Answer 12

difference in a specific part of the genome in a species; gene with at least two alleles

Question 13

What is a recessive lethal allele?

Answer 13

A recessive allele that codes for a lethal trait

Question 14

What phenotypic ratio are offspring of heterozygous individuals with lethal alleles represented in?

Answer 14

thirds

Question 15

What is dominant recessive allele?

Answer 15

An dominant allele that is lethal when homozygous

Question 16

What is consanguinity and a consequence?

Answer 16

Mating with a close relative; increase chance of homozygous lethal genotype

Question 17

What is epistasis?

Answer 17

Expression of a gene in influenced by expression of another

Question 18

When does a 15:1 ratio result?

Answer 18

Epistasis; presence of a dominant allele in either one of two genes causes expression of one phenotype

Question 19

How does a 9:3:3:1 ration or 9:4:3 ration result in epistastis?

Answer 19

homozygous recessive for one of two genes masks the dominant trait

Question 20

What are complementary genes?

Answer 20

Both genes require a specific allele for phenotype to occur

Question 21

How does 9:7 phenotypic ratio arise?

Answer 21

If one of the genes in homozygous, one trait occurs; Both genes require dominant allele to have other trait

Question 22

What is a polygenic trait?

Answer 22

When one trait is influenced by multiple genes

Question 23

What is penetrance?

Answer 23

Whether or not a phenotype persists despite individual having the genotype

Question 24

What is polydactyly?

Answer 24

Having more fingers than normal

Question 25

What is variable expressivity?

Answer 25

Individuals share the same genotype for an allele differ in severity of phenotype allele produces

Question 26

What is norm of reaction?

Answer 26

Spectrum of phenotypic variations from a single genotype as a result of environmental conditions

Question 27

What is phenotypic plasticity?

Answer 27

Ability of a single genotype to produce variable phenotypes depending on environmental conditions

Question 28

What are conditional mutations?

Answer 28

Gene expresses mutant phenotype in specific environmental conditions and normal/wild-type phenotype in typical conditions