Extensions To Mendel's Rules Part I

Question 1

True or false: multifactorial inheritance is responsible for the greatest number of individuals who will need clinical intervention because of genetic diseases.

Answer 1

True

Question 2

What is non-Mendelian inheritance?

Answer 2

Any pattern of inheritance in which traits do not aggregate in accordance with Mendel’s laws.

Question 3

What is one of the most earliest and important events during embryological development?

Answer 3

Establishing polarity

Question 4

What are the three types of dominance?

Answer 4

Complete dominance

Incomplete dominance

Codominance

Question 5

What is complete dominance?

Answer 5

Phenotype of the heterozygote is the same as the phenotype of one of the homozygotes.

Question 6

What is incomplete dominance?

Answer 6

Phenotype of the heterozygote is intermediate (falls within the range) between the phenotypes of the two homozygotes.

Question 7

What is codominance?

Answer 7

Phenotype of the heterozygote includes the phenotypes of both homogzygotes.

Question 8

What is penetrance?

Answer 8

The percentage of individuals having a particular genotype that expresses the expected phenotype.

Question 9

What is expressivity?

Answer 9

The degree to which a character is expressed.

Question 10

Assume that long fingers are inherited as a recessive trait with 80% penetrance. Two people heterozygous for long fingers mate. What is the probability that their first child will have long fingers?

Answer 10

1/4 x 80% = 20%

Question 11

What are the consequences of a lethal allele?

Answer 11

It causese death at an early stage of development, and so some genotypes may not appear among the progeny.

It also affects the Mendelian genotypic and phenotypic ratios in progeny.

Question 12

A cross between two green corn plans yields 2/3 progeny that are green and 1/3 that are white.

What is the genotype of the green progeny and the white progeny?

Answer 12

White genotype: GG
Green genotype: Gg
gg: lethal allele causing death in homozygous

Question 13

What is the significance of multiple alleles?

Answer 13

For a given locus, more than two alleles are present within a group of individuals.

ABO blood group is an example.

Question 14

What blood types are possible among the children of a cross between a ma who is blood type A and a woman of blood type B?

Answer 14

Could be a type with AA and Ai,
Could be B type with BB or Bi
Could be AB with AB
Could be O type with ii

Question 15

What is mean by gene interaction?

Answer 15

The effects of genes at one locus depend on the presence of genes at another loci.

A gene interaction may produce novel phenotypes, or a gene interaction with epistasis is possible, in which one gene masks the effects of another gene.

Question 16

When does gene interaction take place?

Answer 16

When genes at multiple loci determine a single phenotype.

Question 17

What is epistasis?

Answer 17

When one gene masks or influences the effect of another gene.

Question 18

What is an example of epistasis?

Answer 18

The coat color of mice.

The epistatic gene C determines whether pigment will be deposited into hair or not (dominant is C)

The second gene B determines what pigment is deposited, black (B) or brown (b).

An individual that is cc has a white coat regardless of the genotype of the second gene.

Question 19

What is the phenotypic ratio produced from a standard dihybrid cross?

Answer 19

9:3:3:1

Question 20

What types of dominance are present in cystic fibrosis?

Answer 20

Complete dominance

Co-dominance

Incomplete dominance

Question 21

What is pleiotropy?

Answer 21

When one gene is able to affect multiple phenotypic characteristics.

Question 22

What is a single-gene disorder the result of?

Answer 22

A single mutated gene.