test 1

Question 1

What is the difference between monohybrid and dihybrid crosses?

Answer 1

A monohybrid cross is a cross in the F1 generation of parents that differ in one trait. A dihybrid cross is a cross in the F1 generation of parents that differ in two traits.

Question 2

What are homologous chromosomes?

Answer 2

A set of chromosomes, one maternal and one paternal for the same type of chromosomes

Question 3

What is the difference between monomorphic and polymorphic genes?

Answer 3

A monomorphic gene has one common, wild-type allele. A polymorphic gene has more than one common, wild-type allele.

Question 4

What is the law of segregation?

Answer 4

States that a gene will separate into different gametes during gamete formation, meaning every individual has two alleles for a gene but only one passes to their offspring. Refers to one gene.

Question 5

What is the law of independent assortment?

Answer 5

States that the inheritance of one pair of genes is independent of the inheritance of another pair. Refers to more than one gene.

Question 6

What is the product rule?

Answer 6

States that the probability of multiple events all occurring is the probability of each event multiplied together.

Question 7

What is the sum rule?

Answer 7

States that the probability of this event or that event occurring is the probability of each event added together.

Question 8

What is a vertical pattern of inheritance?

Answer 8

At least one person in each generation is affected by the trait. An affected person has at least one affected parent. Suggests a dominant trait.

Question 9

What is a horizontal pattern of inheritance?

Answer 9

Every generation does not have affected individuals. Parents do not have to be affected to pass the trait on to their children. Suggests a recessive trait

Question 10

What is a testcross?

Answer 10

If the phenotype of an individual is known but the genotype is not, the individual is crossed with a homozygous recessive individual for that trait. If the offspring all show the dominant trait (same phenotype as unknown), then the individual is homozygous dominant for the trait. If the offspring show half dominant and half recessive traits, the individual is heterozygous dominant.

Question 11

What is self-fertilization?

Answer 11

A cross between a female gamete and male gamete from the same individual.

Question 12

What is cross-fertilization?

Answer 12

A cross between a female gamete of one individual and a male gamete of another individual.

Question 13

What is a reciprocal cross and what is the purpose?

Answer 13

In order to test the parent’s role of inheritance on their offspring, two individuals are crossed with the opposite phenotype of each sex then what was the phenotypes of the parent generation.

Question 14

What is pleiotropy

Answer 14

When one gene affects multiple traits. Shows multiple phenotypes.

Question 15

What is different and what is the same between codominance and incomplete dominance?

Answer 15

Incomplete dominance is when neither phenotype is dominant and the phenotype is an intermediate between the dominant and recessive phenotype. Codominance is when both phenotypes are present so both are dominant. Both incomplete and codominance have a heterozygous genotype.

Question 16

What does a 3:1 phenotypic ratio mean?

Answer 16

One allele is dominant over the other and the heterozygous genotype shows the dominant phenotype.

Question 17

What does a 2:1 phenotypic ratio mean?

Answer 17

The recessive allele is homozygous for lethality.

Question 18

What does a 1:2:1 phenotypic ratio mean?

Answer 18

The heterozygous genotype shows either codominance or incomplete dominance.

Question 19

What does a 9:3:3:1 phenotypic ratio mean?

Answer 19

Indicates that 2 genes are acting independently in a dominant and recessive manner for that trait.

Question 20

How would you find out the genotype of an individual with incomplete or codominance? Would a testcross be needed?

Answer 20

You would not need a testcross. If the other two phenotypes are known, you would know that the genotype of an incomplete or codominant individual would be heterozygous.

Question 21

What causes incomplete dominance and codominance? How do we represent the genotypes using letters?

Answer 21

In regards to colour, both phenotypes are dominant for pigment. Incomplete and codominance are caused by pigments, not enzymes. So both phenotypes are represented using capital letters with superscripts.

Question 22

What is a back-cross and what does it achieve?

Answer 22

When an individual from the F1 generation is crossed with an individual from the parent generation. It achieves offspring that have limited number of traits from one of the parents.

Question 23

What is the genotype of the parents who have the same phenotype, if their offspring show three different phenotype?

Answer 23

The parents have to be heterozygous because there are new phenotypes.

Question 24

Is colouring in Zebras a result of codominance? Why or why not?

Answer 24

No it isn’t. If it was codominance then we would see completely black and completely white Zebras too.

Question 25

How would you reveal a dominance series?

Answer 25

You would do reciprocal crosses between pure-breeding lines for all phenotypes.

Question 26

If an allele is wild-type, does that mean it is the dominant allele?

Answer 26

No. Wild-type alleles have a frequency greater than 1% in the population. It doesn’t necessarily have to be the dominant allele.

Question 27

What does multifactorial inheritance or polygenic mean?

Answer 27

A phenotype appearing from the effects of two or more genes. Or a phenotype appearing from interactions between genes and the environment.

Question 28

What is complimentary gene action?

Answer 28

When two or more genes work in the same metabolic pathway to produce one trait (phenotype).

Question 29

What is a heterogeneous trait?

Answer 29

A trait caused by complimentary gene action. A mutation at any one of a number of genes can cause the same phenotype.

Question 30

What does a 9:7 phenotypic ratio mean?

Answer 30

Indicates complimentary gene action. In other words, indicates that the trait is heterogeneous.

Question 31

What is complementation testing and what is it used for?

Answer 31

Complementation testing can be used to figure out if 1 or multiple genes are involved in producing a particular phenotype. It can also be used to determine if two individuals have mutations in the same gene.

Question 32

What does mutation in different and in the same genes indicate?

Answer 32

When the mutations are in different genes for each parent, there is complementation. When the mutation is in the same gene in each parent, there is no complementation.

Question 33

What is recessive epistasis?

Answer 33

When the homozygous recessive alleles of one gene mask the alleles of another gene. If one gene masks the expression of another, it is epistatic to that gene.

Question 34

What does a 9:3:4 phenotypic ratio mean?

Answer 34

Indicates recessive epistasis.

Question 35

What is another word for complementation?

Answer 35

Reciprocal recessive epistasis.

Question 36

What is the difference between complementation and recessive epistasis?

Answer 36

Complementation works via two genes using the SAME metabolic pathway. Recessive epistasis works via two genes using TWO metabolic pathways.

Question 37

What is dominant epistasis?

Answer 37

When the dominant allele of one gene masks the affects of another gene. The gene that masks the affects of another is epistatic to that gene.

Question 38

What does a 12:3:1 phenotypic ratio mean?

Answer 38

Indicates dominant epistasis.

Question 39

What is penetrance?

Answer 39

The percentage of a population with a particular genotype that have a expected phenotype. The individuals either show the trait or don’t.

Question 40

What is expression?

Answer 40

The degree or intensity with which the expected phenotype is shown for a particular genotype in a population. The individuals show the trait with varying degree or intensity.

Question 41

Can we predict the expression for a particular phenotype?

Answer 41

No.

Question 42

What is complete and incomplete penetrance?

Answer 42

Complete penetrance is when every member of a population with a particular genotype shows the expected phenotype. Incomplete penetrance is when not all of the members of a population with a particular genotype show the expected phenotype.

Question 43

What is constant and variable expression?

Answer 43

Constant expression is when the individuals with a particular genotype in a population show the expected phenotype uniformly/with the same level of intensity. Variable expression is when the individuals with a particular genotype in a population show the expected phenotype but with varying degrees of intensity.

Question 44

Can sex influence penetrance and expressivity?

Answer 44

Yes.

Question 45

What are sex-linked traits?

Answer 45

Traits found on the X or Y chromosome.

Question 46

What are sex-limited traits?

Answer 46

Traits found on autosomal genes that affect one sex but not the other.

Question 47

What are sex-influenced traits?

Answer 47

Traits found on autosomal genes that affect individuals differently depending on their sex. Traits show up in both sexes but their expression differs.

Question 48

How do penetrance and expressivity relate to sex-limited and sex-influenced traits?

Answer 48

Sex-limited traits are an example of incomplete penetrance. Sex-influenced traits are an example of variable expression.

Question 49

What is temperature-sensitive expression?

Answer 49

When the temperature affects the expression of a genotype.

Question 50

What is conditional lethality?

Answer 50

When a particular genotype is lethal only under specific conditions.

Question 51

What are restrictive and permissive conditions?

Answer 51

Restrictive conditions are those which cause a particular genotype to be lethal. Permissive conditions are those which allow life for the same genotype.