Test 4: Genetics 2 Variations Flashcards
Incomplete dominance
when the phenotype of the heterozygote displays a distinct, intermediate phenotype between the two homozygotes
Codominance
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
In cases of __, dominance hierarchies can exist (such as a wild type allele)
multiple alleles
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.
wild-type; “dosage”
Autosome
any of the non-sex chromosomes
When a gene is present on the X chromosome, but not on the Y chromosome, it is said to be __.
X-linked
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
hemizygous; irrelevant
Drosophila males
lack a second allele copy on the Y chromosome
Females must inherit recessive X-linked alleles from __ of their parents in order to express the trait.
both
Males must inherit __recessive X linked trait in order to to express it, making them __ likely to have an X linked disorder than females
One; more
Sex linked disorders in Y chromosomes are __ and usually related to __.
Rare; infertility
Pedigree chart
a diagram that models the inheritance of phenotypes from one generation to the next
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.
horizontal; Vertical; left to right
In a pedigree chart, females are symbolized by a __ and males are symbolized by a __.
circle; square
On a pedigree chart, shading shows
that the individual is affected by the disease or condition.
Pedigrees can be used to study the genetics of inherited diseases. They can be analyzed to determine whether a genetic condition is
autosomal or sex-linked, and whether it is dominant or recessive.
The most common modes of inheritance are __(4).
autosomal recessive, autosomal dominant, X-linked recessive, and X-linked dominant
autosomal recessive
meaning that the gene involved is found on an autosome, and affected individuals have two copies of the allele that causes the condition.
With autosomal recessive inheritance, males and females are __ to be affected.
equally likely
Autosomal Dominant Inheritance
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
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 __
two; cannot; which allele they inherit on the X chromosome.
There is no father-to-son transmission of __.
X-linked traits.
With x-linked traits, sons of an affected mother will __ affected because __.
all be; there is no father-to-son transmission of X-linked traits.
To assign genotypes to individuals on a pedigree chart representing an X-linked recessive trait, it is important to recognize two things __
- 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
In x-link dominant inheritance __daughters will be affected if their father is affected because__
All; he only has 1 x-chromosome to pass on and it must be mutated if he is affected.
In epistasis, the interaction between genes is __, such that one gene __ with the expression of another.
antagonistic; masks or interferes
Polygenic inheritance
multiple genes work together to determine the phenotype of a particular characteristic AND each of these genes encodes the same function.
An allele is RECESSIVE if there are affected __ who have __ parents.
children; two unaffected
An allele is DOMINANT if there are affected __ who have one or more unaffected __.
parent(s), children
The allele is Y-linked if
affected sons have affected fathers
The allele is X- linked if
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.