Test 4: Genetics 2 Variations

Question 1

Incomplete dominance

Answer 1

when the phenotype of the heterozygote displays a distinct, intermediate phenotype between the two homozygotes

Question 2

Codominance

Answer 2

both alleles of a particular gene are expressed in a dominant fashion, meaning both alleles for the same characteristic are simultaneously expressed in the heterozygote

Question 3

In cases of __, dominance hierarchies can exist (such as a wild type allele)

Answer 3

multiple alleles

Question 4

The complete dominance of a __ phenotype over all others often occurs as an effect of __ of a specific gene product, such that the wild-type allele supplies the correct amount of gene product whereas the mutant alleles cannot.

Answer 4

wild-type; “dosage”

Question 5

Autosome

Answer 5

any of the non-sex chromosomes

Question 6

When a gene is present on the X chromosome, but not on the Y chromosome, it is said to be __.

Answer 6

X-linked

Question 7

Males are said to be __, because they have only one allele for any X-linked characteristic. This makes the descriptions of dominance and recessiveness __ for XY males

Answer 7

hemizygous; irrelevant

Question 8

Drosophila males

Answer 8

lack a second allele copy on the Y chromosome

Question 9

Females must inherit recessive X-linked alleles from __ of their parents in order to express the trait.

Answer 9

both

Question 10

Males must inherit __recessive X linked trait in order to to express it, making them __ likely to have an X linked disorder than females

Answer 10

One; more

Question 11

Sex linked disorders in Y chromosomes are __ and usually related to __.

Answer 11

Rare; infertility

Question 12

Pedigree chart

Answer 12

a diagram that models the inheritance of phenotypes from one generation to the next

Question 13

On a pedigree chart, Individuals connected by a __ line have mated and had children. __ lines connect parents to their children. Siblings are generally shown from __ according to birth order.

Answer 13

horizontal; Vertical; left to right

Question 14

In a pedigree chart, females are symbolized by a __ and males are symbolized by a __.

Answer 14

circle; square

Question 15

On a pedigree chart, shading shows

Answer 15

that the individual is affected by the disease or condition.

Question 16

Pedigrees can be used to study the genetics of inherited diseases. They can be analyzed to determine whether a genetic condition is

Answer 16

autosomal or sex-linked, and whether it is dominant or recessive.

Question 17

The most common modes of inheritance are __(4).

Answer 17

autosomal recessive, autosomal dominant, X-linked recessive, and X-linked dominant

Question 18

autosomal recessive

Answer 18

meaning that the gene involved is found on an autosome, and affected individuals have two copies of the allele that causes the condition.

Question 19

With autosomal recessive inheritance, males and females are __ to be affected.

Answer 19

equally likely

Question 20

Autosomal Dominant Inheritance

Answer 20

a single mutant allele is sufficient to cause the condition because the mutant allele is dominant over the normal allele. **effects male and female equally

Question 21

X-linked Recessive Inheritance: Females must inherit __ copies to display an X-linked recessive condition. Males __ be carriers; they will either be affected or unaffected, depending on __

Answer 21

two; cannot; which allele they inherit on the X chromosome.

Question 22

There is no father-to-son transmission of __.

Answer 22

X-linked traits.

Question 23

With x-linked traits, sons of an affected mother will __ affected because __.

Answer 23

all be; there is no father-to-son transmission of X-linked traits.

Question 24

To assign genotypes to individuals on a pedigree chart representing an X-linked recessive trait, it is important to recognize two things __

Answer 24

1. Males only have one copy of the X chromosome and females have two copies, and 2) the presence of one normal allele will result in an unaffected individual

Question 25

In x-link dominant inheritance __daughters will be affected if their father is affected because__

Answer 25

All; he only has 1 x-chromosome to pass on and it must be mutated if he is affected.

Question 26

In epistasis, the interaction between genes is __, such that one gene __ with the expression of another.

Answer 26

antagonistic; masks or interferes

Question 27

Polygenic inheritance

Answer 27

multiple genes work together to determine the phenotype of a particular characteristic AND each of these genes encodes the same function.

Question 28

An allele is RECESSIVE if there are affected __ who have __ parents.

Answer 28

children; two unaffected

Question 29

An allele is DOMINANT if there are affected __ who have one or more unaffected __.

Answer 29

parent(s), children

Question 30

The allele is Y-linked if

Answer 30

affected sons have affected fathers

Question 31

The allele is X- linked if

Answer 31

Mothers pass it on to both sons and/or daughters, while fathers pass it on to all of their daughters but none of their sons.