midterm - modification of mendelian genetcs Flashcards
___ is the joint expression of both alleles in a heterozygote
Codominance
If two alleles of a single gene are responsible for producing two distinct, detectable gene products, a situation called ___ occurs
codominance
The MN blood group in human illustrates this codominance and is characterized by an antigen called a
___ found in the surface of RBCs
glycoprotein
The ___ is under the control of an autosomal locus on chromosome 4 and two alleles
designated LM and LN
MN system
Three combinations are possible, each resulting in a distinct blood type
CODOMINANCE
Mutations can modify the information stored in a gene, and each change produces a different allele
MULTIPLE ALLELES
When three or more alleles of the same gene are found, ____ are present that create a
unique mode of inheritance
multiple alleles
The ___ have 3 alternative alleles
ABO blood group
It is characterized by the presence of antigens on the surface of RBCs
ABO blood group
Mutations resulting in the synthesis of a gene product that is nonfunctional can be often tolerated in
the heterozygous state; one wild-type allele may be sufficient to produce essential product to allow
survival
LETHAL GENES
However, such mutations behaves as a recessive lethal allele and homozygous recessive individuals will
not survive
LETHAL GENES
In mammals, this might occur during development, early childhood, or even adulthood
LETHAL GENES
The presence of just one copy of the allele results in the death of the individual
dominant lethal allele
The effects of two or more genes on a single characteristic, the converse situation, where expression of
a single gene has multiple phenotypic effects, is also quite common
PLEIOTROPY
pleiotropy
EXAMPLE is ___ an autosomal dominant mutation in the gene encoding the connective
tissue protein fibrillin
Marfan syndrome,
Phenotypes associated with __ includes lens dislocation, increased risk of aortic
aneurism, and lengthened long bones in limbs
Marfan syndrome
Males cannot be homozygous or heterozygous for X linked genes, and this condition is referred to as
being ___
hemizygous
Gene expression may be affected by the gender of an individual even when genes are not on the X
chromosom
SEX LIMITED AND SEX-INFLUENCED
*_____ –expression of a specific phenotype is absolutely limited to one gender
Sex-limited
—-–the gender of an individual influences the expression of a phenotype but the
phenotype is expressed in both gender
Sex-influenced
in both cases, ___ are responsible for the existence of contrasting phenotypes, but the
expression of such genes is dependent on the hormone constitution of the individual
autosomal genes
Hen feathering is due to dominant allele, iss an examle of
SEX-LIMITED INHERITANCE
*___ inheritance include pattern baldness in humans
Sex-influenced
utosomal genes are responsible for the phenotypes, but the expression of the genes is dependent on
the hormonal constitution of the individua
SEX-INFLUENCED INHERITANCE
The heterozygous genotype exhibits one phenotype in one sex and the contrasting one in the other
sEX-INFLUENCED INHERITANCE
____ –phenotype is determined by the genetic information expressed in the gamete of the
mother; following fertilization, the developing zygote’s phenotype is influenced not by the individual’s
genotype, but by gene products directed by the genotype of the mother.
Maternal effect
___–the phenotype is affected by the expression of genes contained in the DNA of
mitochondria rather than the nucleus
Organelle heredity
Gene interaction are those that reveal the phenomenon of ___
epistasis
*___ –the expression of one gene or gene pair masks or modifies the expression of another gene
or gene pair (can be antagonistic or complementary)
Epistasis
For example, the homozygous presence of a recessive allele prevents or overrides the expression of
other alleles at a second locus
epistasis
Another example, a single dominant allele at the first locus influences the expression of the alleles at as
second gene locus
epistasis
When the alleles masking another gene on another locus is recessive, this is called ___
▪ *
recessive epistasis
___ occurs when a dominant allele at one genetic locus masks the expression of the
alleles at a second locus
Dominant epistasis
