Ch. 4 Flashcards
An individual with two identical alleles for a gene is ___ for that gene
homozygous
An individual with two different alleles is
heterozygous
The __ describes the outward expression of an allele combination.
phenotype
A ___ phenotype is a variant of a gene’s expression that arises when the gene undergoes a change.
mutant
One trait that masks another is __ trait.
dominant
The most common expression of a particular allele combination is called the ___ phenotype.
wild type
Monogenic
mutations in single genes
Modes of inheritance
patterns in which single-gene traits and disorders occur in families
Autosomal dominant
affects both sexes w/ equal frequency and appears in every generation
ex. Huntington disease
affected individuals may be heterozygous
Autosomal recessive
affects both sexes and can skip generations through carriers
ex. cystic fibrosis
affected individuals are always homozygous
Hemizygous
having a single copy of gene instead of customary 2 copies
all genes on single X chromosome in males are hemizygous
X-Linked Traits
females have 2 X chromosomes (can be heterozygous or homozygous for x-linked traits)
males have 1 X chromosome, hemizygous for all x-linked straight
Disorders w/ X-Linked Recessive Inheritance Patterns
- more common than X-Linked dominant traits
- hemizygous males & homozygous recessive females are affected
- males carrying one X-linked recessive allele express the recessive phenotype
- more common in males, rare traits exclusive to males
- affected males pass affected allele to all daughters but none to sons
ex. color blindness
Paternal Inheritance
genes from the Y chromosome are passed directly from father to son
Y-linked genes are all expressed (hemizygous for males)
If a father has a Y chromosome-linked disease, what is the chance of his son getting this disease? How about his daughter?
Son: 100% Daughter: 0%
If a father has a X-linked dominant disease, what is the chance of his son getting this disease? How about his daughter? (assuming the mother is a healthy female?)
Son: 0% Daughter 100%
If a father has a X-linked recessive disease, what is the chance of his son getting this disease? How about his daughter? (assuming the mother is a healthy female)
Son: 0% Daughter: 0% disease but 100% carrier
If a trait is autosomal dominant, then an individual who expresses the trait may have parents who do not express the trait.
False; they have at least one parent with the trait (unless they had a de novo mutation)
An autosomal dominant trait may be transmitted from father to son.
True; Autosomal dominant traits can be transmitted regardless of the sex of the parents and children.
Individuals who express autosomal recessive traits are always homozygous.
True; Affected individuals with an autosomal recessive trait have a homozygous recessive genotype.
Autosomal recessive traits never skip a generation
False; can skip a generation
Individuals who express autosomal dominant traits are always homozygous.
False; can be heterozygous or homozygous
Similar to the inheritance of single-gene diseases, infectious disease inheritance can be easily calculated.
False
Single-gene diseases can be much more common in some populations than in others
True
If an individual has the allele(s) for a single-gene disease, they will definitely become ill with the disease
False
Some genetic diseases may be treated by providing a missing enzyme or protein
True
Single-gene traits and diseases are called Mendelian.
True
Based on Mendel’s laws of independent assortment and segregation, what are the possible gametes for a cell with the genotype CCBb?
CB and Cb
