Chapter 4: Non Mendelian Genetics (Modifications in the Mendelian Ratios) Flashcards
A mutation in a genes that causes diminution or the loss of the specific wild-type function.
Loss-of-function mutation
When a mutation causes a complete loss of function in the genes, the resulting mutated gene si called?
Null allele
Total loss of function mutation causes the gene product to lose?
affinity to its substrate
A mutation that enhances the function of the wild-type product.
Gain-of-function mutation
What effect does a gain-of-function mutation confer?
Increased gene product. In such a case, the mutation may be affecting the regulation of the transcription of the gene under study.
Gain-of-function mutation generally results to?
Dominant allele. Since one copy of in a diploid organism is sufficient to alter the normal phenotype.
A mutation in the genes where no change in function can be detected.
Neutral mutation
This happens when neither of the alleles for a specific trait comes dominant (both of alleles are expressed resulting in intermediate expression of the overt phenotype).
Incomplete dominance
True or False. Even when complete dominance seems apparent, careful examination of the gene product, rather than the phenotype, often reveals an intermediate level of gene expression
True. For example is Tay-Sachs disease
This happens when two contrasting alleles are phenotypically expressed. It is characterized by distinct expression of the gene products of both alleles.
Codominance
Two forms of glycoprotein that exist in MN blood group.
- M glycoprotein
2. N glycoprotein
Examples of codominance:
- MN blood group
2. ABO blood group
True or False. In the ABO blood group, the presence of the A and B antigens are codominant and the absence of either of them results in O type.
True
Specificity of the A and B antigens is based on?
Terminal sugar of the carbohydrate group.
Both the A and B antigens are derived from a precursor molecule called?
H substance
The incompleteness of the H substance leads to?
Blood type O because an incompletely formed H substance will not be enough substrate for the enzyme that normally adds the terminal sugar.
Individuals that are homozygous for this mutated gene cannot synthesize the complete H substance.
Fucosyltransferase 1 gene
FUT1 gene encodes what enzyme?
Fucosyl transferase
A mutation resulting in the synthesis of an essential gene product that is nonfunctional.
Lethal allele
A mutation resulting in the synthesis of a gene product that is nonfunctional can be often tolerated in the heterozygous state.
Recessive lethal allele
True or False. For an individual heterozygous for a lethal allele, one wildtype allele is not sufficient to produce enough of the essential product to allow survival.
False.
True or False. In some cases, recessive lethal allele may take on the form of a dominant trait when present heterozygously.
True. Yellow allele in mice is dominant to the wild-type agouti allele. The yellow allele is also a recessive lethal allele because the presence of two copies of the yellow allele kills a mouse before birth.
Presence of just one copy of this allele results in the death of an individual.
Dominant lethal allele
Huntington’s disease is caused by?
Dominant autosomal allele H
True or False. The onset of the Huntington’s disease in heterozygotes (Hh) is delayed usually well into adulthood
True
The cellular function of numerous gene products contributes to the development of a common phenotype.
Gene interaction
Is often used to describe the idea that several genes influence a particular characteristic.
Gene interaction
Each step of development increases the complexity of a sensory organ and is under the control and influence of one or more genes. This is an example of what phenomenon.
Epigenesis
Mutations that interrupt many of the steps of ear development lead to a common phenotype causes what condition?
Hereditary deafness
A mutated phenotype where multiple genes are involved.
Heterogenous trait
A phenomenon where the expression of one gene or gene pair masks or modifies the expression of another gene.
Epistasis
True or False. In epistasis, genes involved control the expression of the same general phenotypic characteristic in a constructive manner.
False.
Homozygous presence of a recessive allele prevents or overrides the expression of other alleles at a second locus (or several other loci) such that of the Bombay phenotype. This is an example of?
Epistasis
One of the epistasis-participating genes that is expressed.
Epistatic allele
One of the epistasis-participating alleles that is masked.
Hypostatic allele
True or False. ABO blood type is an example of recessive epistasis where the presence of two wild-type FUT1 gene is needed to phenotypically express either A or B blood types.
True
A presence of homologous recessive trait masks the expression of another gene.
Recessive Epistasis
Occurs when a dominant allele at one genetic locus masks the expression of the alleles at a second locus.
Dominant Epistasis
At least one of the dominant allele must be present to produce pigmentation because the homozygous nature of any of the two recessive allele masks the dominant trait.
Complementary Epistasis
Fruit shape in Cucurbita pepo is a novel phenotype, a dominant allele at any one of the loci gives what fruit?
Sphere-shaped fruit
Fruit shape in Cucurbita pepo is a novel phenotype, absence of a dominant allele on both of the loci gives what fruit?
Long-shade fruit
Fruit shape in Cucurbita pepo is a novel phenotype, the presence of a dominant allele on both of the loci gives what fruit?
Disc-shaped fruit
This technique allows for the determination of whether two alleles are of the same gene or whether they represent mutations in separate genes.
Complementation Analysis
True or False. In complementation analysis, if the F1 progeny developed the normal phenotype, then two recessive mutations are in separate genes and are not alleles of one another.
True
True or False. In complementation analysis, if the F1 progeny developed the mutated phenotype, then two recessive mutations affect the same gene and are alleles of one another.
True
The expression of a single gene has multiple phenotypic effects.
Pleiotropy
Human malady resulting from an autosomal dominant mutation in the gene encoding the connective tissue protein fibrillin.
Marfan Syndrome
Afflicted individuals cannot adequately metabolize the porphyrin component of hemoglobin when this respiratory pigment is broken down as red blood cells are replaced.
Porphyria variagata
Marfan Syndrome and Porphyria variagata are examples of what?
Genes having multiple phenotypic effects
A condition of having only one possible locus for a specific gene.
hemizygous
White eye mutation in Drosophila is an example of?
X-linkage
An inheritance pattern where phenotypic traits controlled by recessive X-linked genes are passed from homozygous mothers to all sons
Crisscross pattern of inheritance
Crisscross pattern occurs because?
Females exhibiting a recessive trait carry the mutant allele on both X chromosome
Colorblindness in humans is an example of?
X-linked disease
Duchenne muscular dystrophy in humans is an example of?
X-linked disease
The expression of a specific phenotype is absolutely limited to one sex.
Sex-limited
Hen and cock feathering in fowl is an example of?
Sex-limited trait
True or False. In both sex-limited and sex-influenced inheritance, autosomal genes
are responsible for the existence of contrasting phenotypes, but the expression of these genes is dependent on hor-
mone constitution of the individual.
True.
Pattern baldness in humans is an example of?
Sex-influenced trait
Autosomal genes are responsible for the contrasting phenotypes displayed by both males and females, but the expression of these genes is dependent on the hormonal constitution of the individual.
Sex-influenced
The percentage of individuals who show at least some degree of expression of a mutant genotype.
Penetrance
Reflects the range of expression of the mutant genotype.
Expressivity
True or False. The physical location of a gene in relation to other genetic material may influence its expression.
True
Mutations whose expression is affected by temperature
Temperature-sensitive mutations
True or False. All genetic traits become apparent at the same time during an organism’s life span.
False
Only one or a few of the organelles contain a mutant gene in a cell among a population of mostly normal mitochondria, the corresponding mutant phenotype may not be revealed.
Heteroplasmy
Strain of Saccharomyces cerevisiae a deficiency in cellular respiration involving abnormal electron transport..
Poky strain