Question 1

Genetic crosses which involve two traits are referred to as phenotypic crosses.

Accepted Answer

Genetics crosses are called dihybrid crosses when they are examining two traits.

Question 2

Figure:
Use the following figure to answer question. 
-This figure shows a dihybrid cross.What does "a" represent?

Accepted Answer

See Figure 10.03 and associated text.

Question 3

If a biologist wanted to manually cross-fertilize two pea plants,which of the following steps must be taken?

Accepted Answer

Pea plants normally self-fertilize,but they can be cross-pollinated by an experimenter who manually transfers pollen from an anther of one plant to the carpel of another plant.

Question 4

When an organism has two identical alleles for a trait we would refer to this condition as:

Accepted Answer

When an organism has two identical alleles for one gene,it is homozygous.

Question 5

What are alleles?

Accepted Answer

The units of inheritance are alleles of genes.In an individual,each trait has two alleles (alternate forms of a gene),and the dominant allele masks expression of the recessive allele.

Question 6

If pairs of factors separate independently of other pairs of factors,you are dealing with the

Accepted Answer

The law of independent assortment states the following: F1F1F1S1F1F1F10 Each pair of factors separates (assorts)independently (without regard to how the others separate).F1F1F1S1F1F1F10 All possible combinations of factors can occur in the gametes.

Question 7

Mendel's law of segregation implies that the two members of an allelic pair

Accepted Answer

Mendel's law of segregation explains that an individual has two factors for each trait,which separate during gamete formation so that each gamete contains only one factor from each pair.

Question 8

Which of the following terms would be used for an allele which can mask the expression of another allele?

Accepted Answer

The dominant allele is named because of its ability to mask the expression of the other allele,called the recessive allele.

Question 9

In humans,brown eyes (B)are dominant over blue eyes (b).If a homozygous brown-eyed woman mates with a homozygous blue-eyed man,what would be the chances of producing a blue-eyed child?

Accepted Answer

BB (brown)crossed with bb (blue)produces 100% Bb (brown).

Question 10

Which of the following terms is represented by word descriptions,such as brown or tall?

Accepted Answer

Phenotype refers to an individual's physical appearance.Genotype refers to the genes of an individual,and indicated by letters.

Question 11

A woman who can roll her tongue (presumably dominant)is married to a man who cannot.Two of their four children can roll their tongues and two cannot.What is the genotype of the parents?

Accepted Answer

Father and children who cannot roll tongue must be genotype "aa".So each parent must have given one "a" allele.Mother must be "Aa".

Question 12

In a Mendelian monohybrid cross,which generation is always completely heterozygous.

Accepted Answer

Mendel first did monohybrid crosses that involved only one trait.He began with a P generation (two homozygous parents),and that was followed by an F1 generation (heterozygous)and then an F2 generation (3:1 ratio).

Question 13

If an organism shows a recessive phenotype,such as short pea plants,it can be

Accepted Answer

Homozygous recessive (tt)individual shows the recessive phenotype and is short.

Question 14

In humans,brown eyes (B)are dominant over blue eyes (b).A brown-eyed woman who has a blue-eyed child would have the genotype

Accepted Answer

The brown-eyed woman could be homozygous dominant (BB)or heterozygous (Bb).But as her blue-eyed child must be homozygous recessive (bb),the mother must have been heterozygous to pass down the recessive allele.

Question 15

Figure:
Use the following figure to answer question. 
-This figure shows a dihybrid cross.What does "e" represent?

Accepted Answer

See Figure 10.03 and associated text.

Question 16

If a genotype of an organism is YySsTt,then what does yST represent?

Accepted Answer

If genotype is YySsTt,this is a diploid organism with two alleles for each gene.Since yST is haploid (one allele for each gene),then it must be the haploid gamete.

Question 17

When an organism has two different alleles for a particular trait,which term best describes this condition?

Accepted Answer

When an organism has two different alleles at a gene locus,we say that it is heterozygous.

Question 18

Because genes close together on a chromosome tend to be inherited together,they are said to form a

Accepted Answer

All of the alleles on any chromosome form a linkage group and will be inherited together unless crossing-over occurs.

Question 19

Which of the following would be an addition to Mendel's Law of segregation?

Accepted Answer

Mendel's law of segregation states that an individual has two factors for each trait,which separate during gamete formation so that each gamete contains only one factor from each pair.

Question 20

In which kind of cross would you expect to find a ratio of 3:1 among the F2 offspring?

Accepted Answer

In Mendel's monohybrid cross,a 3:1 ratio among the F2 offspring was possible if the F1 parents contained two separate copies of each hereditary factor,one of these being dominant and the other recessive.

Quiz 10: Patterns of Genetic Inheritance