Mendelian Inheritance Flashcards
_____ _____ refers to the rather strict rules for inheritance of monogenic traits as first recognized by Gregor Mendel in the 19th century.
Mendelian inheritance
A _____ or single gene trait is one in which the expression is determined by the input of the two alleles of a single gene.
monogenic
Traits or structures that involve the input of more than one gene known as _____ traits.
polygenic
In _____ expression, the two gene alleles are expressed equally.
codominant
In _____ inheritance, the phenotype accurately expresses the genotype. Red flowers must have 2 red gene alleles (homogenous), pink flowers must have one red gene allele and one white gene allele (heterogenous), and white flowers must have two white gene alleles.
codominant
Specific inheritance patterns of a monogenic trait can be assessed without knowing a person’s genotype based on _____ _____.
family history
_____ is the term used to describe how a trait is inherited or passed from one human generation to the next.
Transmission
A _____ (sometimes termed a kinship) is the extended family relationships over several generations.
kindred
A _____ is a pictorial or graphic illustration of family members’ places within a kindred and their history for a specific trait or health problem over several generations.
pedigree
_____-_____ single gene traits have the controlling gene alleles located on an autosomal chromosome.
Autosomal-dominant
Autosomal-dominant traits are found in approximate _____ distribution between male and female family members.
equal
True or false:
An autosomal-dominant trait has a carrier status.
False
the person with even one dominant allele expresses the trait
The autosomal-dominant trait appears in _____ generation with clear transmission from _____ to child.
- every
2. parent
The risk for an affected person with an autosomal-dominant trait who is heterozygous for the dominant allele to pass the trait to his or her child is _____%.
50
The risk for an affected person with an autosomal-dominant trait who is homozygous for the dominant allele to pass the trait to his or her child is _____%.
100
Unaffected people do _____ have the autosomal-dominant allele and have essentially _____ (#) risk for transmitting the trait to their children.
- not
2. zero
A person can be homozygous for the dominant alleles of a normal trait, but not for health disorders because with these disorders, the homozygous autosomal-dominant genotype appears _____, with loss at the embryonic or fetal pregnancy stages or within the first _____ (#) months after birth. This distinction slightly changes the predictability of the disorder.
- lethal
2. 12
Two factors that affect the expression of some autosomal-dominant single gene traits are _____ and _____.
- penetrance
2. expressivity
_____ is how often a gene is expressed within a population when it is present.
Penetrance
The higher degree of _____ of an AD trait, the higher the risk for a person to develop the disease.
penetrance
_____ is a personal issue (rather than a population issue) in which the degree of gene expression varies by the person who has the dominant gene for a health problem.
Expressivity
The gene is _____ expressed, but some people have more severe problems than do other people.
always
A person with low expression of a gene trait can transmit the gene to his or her child who then may have _____ expression of the disorder. The reverse is also true.
high
_____-_____ (AR) traits have the controlling gene alleles on an autosomal chromosome are are expressed _____ when both alleles are present.
- Autosomal-recessive
2. only
An AR trait is found in approximate _____ distribution between male and female family members.
equal
An AR trait often appears first in _____ rather than in the _____ of affected children.
- siblings
2. parents
An AR trait my not appear in _____ generations of any one branch of a family.
all
The risk for children of two affected parents with an AR trait to also be affected is close to _____%.
100
About _____% of the members of a family with an AR trait will express the trait or disorder.
25
True or False:
AR traits do have a carrier status in which those individuals who have only one affected allele may not express any level of the trait.
True
Unaffected carriers of AR traits _____ transmit the trait to their children if their partner is either a carrier or is affected.
can
An AR allele may be present in a family for many generations without overt _____.
expression
The phenotype and _____ are the same for expressed AR traits and disorders.
genotype
A person who has one mutated allele for a recessive genetic disorder is a _____.
carrier
An AR trait carrier is usually not affected and can pass the trait to his or her children. For some AR disorders, a carrier may have very _____ manifestations.
mild
A person who has only one sickle cell gene allele and one normal gene allele for beta glob in usually has about _____% normal hemoglobin and rarely expresses sickle cell health problems.
50
The unique genes on the Y chromosome are all ______ in origin and are expressed only in _____.
- paternal
2. males
_____ of the unique Y chromosome genes are important for male anatomic and sexual development and fertility.
Most
Females have _____ the number of X chromosomes than males.
twice
Because X-linked alleles in the male have no corresponding allele in the Y chromosome, any X-linked allele in a male is expressed as if it were a _____ allele, a condition known as _____.
- dominant
2. hemizygosity
X-linked recessive genes have _____ expression in males and _____ expression in females.
- dominant
2. recessive
X-linked recessive traits are also known as _____-_____ recessive traits.
sex-linked
The incidence of a _____-_____ trait is much higher among males in a family than among females (and my be exclusive to males).
sex-linked
A sex-linked recessive trait _____ be transmitted from father to son.
cannot
Sex-linked recessive trait transmission occurs from an affected father to _____ daughters ( who will be obligate carriers) and from a carrier mother to _____ sons and daughters.
- all
2. both
Female carriers of a sex-linked recessive trait have a _____% risk of transmitting the gene to their children with each pregnancy.
50
If no sons are born to carrier mothers, the sex-linked recessive trait may not be expressed _____ for many generations.
overtly
If no _____ are born to affected fathers with a sex-linked recessive trait who have children with non carrier mothers, the trait is not transmitted further.
daughters
Depending on the sex-linked recessive trait disorder, females who are _____ may not survive pregnancy or will have more severe disease.
homozygous
X-linked dominant disorders are _____.
rare
Females do express the X-linked dominant disorder in the heterozygous state and have a _____% chance of transmitting the trait with each pregnancy to children of either gender.
50
Males who are homozygous for the X-linked dominant allele are _____ profoundly affected than heterozygous females.
more
A father affected by an X-linked dominant disorder transmits the disorder to _____ of his daughters (who then express the disorder) and to _____ of his sons.
- all
2. none
A special genetic feature is present in the somatic cells of females related o the issue of unequal gene alleles for the approximate _____ (#) genes on the X chromosome.
1500
Within the first week of embryonic life in females, these cells all randomly inactivate one _____ chromosome in every cell, to prevent XX females from having an excessive “dose” of the X chromosome genes coding for somatic cell function.
X
As early embryonic cells commit to become a specific type of tissue or organ, the early organ contains only a few cells, and usually this small number of cells is not _____ in maternal-to-paternal percentage for X inactivation.
equal
