Mendelian Genetics MCQs Flashcards
(29 cards)
What is the primary function of a Punnett square in genetic analysis?
a) To determine the age of an organism.
b) To calculate the exact mutation rate of a gene.
c) To predict the genotypes and phenotypes of offspring from a genetic cross.
d) To identify environmental factors influencing gene expression.
e) To analyze the evolutionary history of a species.
c) To predict the genotypes and phenotypes of offspring from a genetic cross.
If a geneticist wants to determine the unknown genotype of a dominant-phenotype individual (e.g., a round pea plant), which type of cross would be most appropriate?
a) A self-cross (crossing the individual with itself).
b) A cross with another dominant phenotype individual.
c) A test cross (crossing with a homozygous recessive individual).
d) A cross with a heterozygous individual.
e) Crossing with a parent with unknown genotype.
c) A test cross (crossing with a homozygous recessive individual).
Which term describes a gene interaction where one gene modifies the expression of another gene, essentially acting as a switch?
a) Pleiotropy
b) Polygenic inheritance
c) Incomplete dominance
d) Epistasis
e) Overdominance
d) Epistasis
In Labrador retriever coat color, the E gene determines whether pigment is deposited, while the B gene determines the color of the pigment (black or chocolate). If a Labrador has the genotype “ee”, regardless of its B alleles, its coat will be yellow. This is an example of what genetic phenomenon?
a) Incomplete dominance
b) Pleiotropy
c) Polygenic inheritance
d) Codominance
e) Epistasis
e) Epistasis
What type of dominance is characterized by a heterozygous phenotype that is an intermediate blend between the two homozygous phenotypes (e.g., pink flowers from red and white parents)?
a) Complete dominance
b) Codominance
c) Overdominance
d) Incomplete dominance
e) Underdominance
d) Incomplete dominance
Which genetic phenomenon describes a situation where the heterozygous genotype has a superior phenotype or higher fitness compared to either homozygous genotype, such as in Sickle Cell Trait conferring malaria resistance?
a) Incomplete dominance
b) Underdominance
c) Overdominance (Heterozygote Advantage)
d) Epistasis
e) Pleiotropy
c) Overdominance (Heterozygote Advantage)
When the heterozygous genotype exhibits a lower fitness or is inferior to both homozygous genotypes, what type of dominance is being displayed?
a) Complete dominance
b) Codominance
c) Incomplete dominance
d) Overdominance
e) Underdominance
e) Underdominance
What is the term for a single gene affecting multiple distinct phenotypic traits, as seen with the sickle cell allele influencing various symptoms and malaria resistance?
a) Polygenic inheritance
b) Epistasis
c) Incomplete dominance
d) Pleiotropy
e) Codominance
d) Pleiotropy
Human height, skin color, and IQ are complex traits influenced by multiple genes. What genetic term describes this type of inheritance?
a) Monogenic inheritance
b) Pleiotropy
c) Polygenic inheritance
d) Epistasis
e) Complete dominance
c) Polygenic inheritance
In genetic counseling, particularly for recessive diseases like Cystic Fibrosis, how are “real-world probabilities” used?
a) To determine the exact date of disease onset.
b) To calculate the risk of a child inheriting a disease based on parental carrier status and known genetic ratios.
c) To identify new genetic mutations.
d) To predict environmental triggers for genetic disorders.
e) To analyze the evolutionary history of the disease.
b) To calculate the risk of a child inheriting a disease based on parental carrier status and known genetic ratios.
What is the primary reason for performing a test cross in genetics?
a) To create new genetic mutations.
b) To determine the sex of an offspring.
c) To infer the unknown genotype of an individual displaying a dominant phenotype.
d) To measure the rate of genetic recombination.
e) To produce genetically identical copies of an organism.
c) To infer the unknown genotype of an individual displaying a dominant phenotype.
When conducting a test cross, what should be the genotype of the known individual used for the cross?
a) Homozygous dominant
b) Homozygous recessive
c) Heterozygous dominant
d) Heterozygous recessive
e) Any genotype, as long as it’s known.
b) Homozygous recessive
In a cross involving an unknown dominant-phenotype individual and a homozygous recessive individual, how do the offspring help reveal the unknown allele?
a) All offspring will display the dominant phenotype, making the test inconclusive.
b) All offspring will display the recessive phenotype, indicating a homozygous dominant unknown parent.
c) Half the offspring reveal the unknown allele by displaying the phenotype associated with the homozygous recessive test parent and the unknown allele.
d) The offspring’s phenotypes are always identical to the unknown parent.
e) The offspring’s genotypes cannot be determined from the phenotypes.
c) Half the offspring reveal the unknown allele by displaying the phenotype associated with the homozygous recessive test parent and the unknown allele.
Which genetic phenomenon is exemplified by individuals heterozygous for the Sickle Cell Trait (HbA/HbS) being protected against malaria and having a survival advantage over both homozygous genotypes (HbA/HbA and HbS/HbS)?
a) Incomplete dominance
b) Underdominance
c) Codominance
d) Overdominance (Heterozygote Advantage)
e) Pleiotropy
d) Overdominance (Heterozygote Advantage)
Which statement best describes the principle of genetic linkage?
a) Alleles on different chromosomes are always inherited together.
b) Alleles located close together on the same chromosome are co-inherited more frequently.
c) Only dominant alleles are linked.
d) Genetic linkage explains why all mutations are harmful.
e) All genes assort independently regardless of their location.
b) Alleles located close together on the same chromosome are co-inherited more frequently.
If 50 out of 500 offspring from a genetic cross are recombinant, what is the genetic distance between the two genes?
a) 100 cM
b) 50 cM
c) 25 cM
d) 10 cM
e) 5 cM
10 cM (50/500 * 100 = 10%)
What is the primary application of two- and three-point test crosses in genetic mapping?
a) To determine the sex of offspring.
b) To identify new gene mutations.
c) To measure genetic distances and determine gene order on a chromosome.
d) To predict the exact phenotype of an individual.
e) To analyze protein expression levels.
c) To measure genetic distances and determine gene order on a chromosome.
A scientist crosses two individuals, each with a different recessive mutation causing the same disease phenotype. Their offspring are phenotypically normal. What does this outcome suggest about the mutations?
a) The mutations are at the same locus.
b) The mutations are dominant.
c) The mutations are at different loci and complement each other.
d) The individuals are homozygous dominant for both mutations.
e) The disease is caused by an environmental factor.
c) The mutations are at different loci and complement each other.
In albinism, a recessive mutation in a gene for pigment production results in a lack of pigment, regardless of the individual’s genotype for hair color. This is an example of which genetic phenomenon?
a) Pleiotropy
b) Polygenic inheritance
c) Incomplete dominance
d) Epistasis
e) Codominance
d) Epistasis
A couple, both of whom are genetically deaf, have children who can hear perfectly. This situation can be explained if:
a) Both parents have dominant mutations for deafness.
b) The children inherited a new dominant mutation for hearing.
c) The parents have different recessive mutations at different gene loci that complement each other.
d) Deafness is a polygenic trait that is not inherited.
e) Environmental factors completely override genetic factors for deafness.
c) The parents have different recessive mutations at different gene loci that complement each other.
Which term describes a single gene that influences multiple distinct phenotypic traits, such as an allele affecting both plumage and testes development in a male animal?
a) Polygenic inheritance
b) Epistasis
c) Incomplete dominance
d) Pleiotropy
e) Codominance
d) Pleiotropy
When a single phenotypic trait, like human height or skin color, is influenced by the cumulative effects of two or more genes, what type of inheritance is this?
a) Monogenic inheritance
b) Pleiotropy
c) Polygenic inheritance
d) Epistasis
e) Mendelian inheritance
c) Polygenic inheritance
What is the key advantage of a three-point test cross over a two-point test cross?
a) It requires fewer offspring to analyze.
b) It can only map dominant genes.
c) It allows simultaneous determination of gene distances and order for three genes.
d) It is simpler to perform in the lab.
e) It only provides information about phenotypes, not genotypes.
c) It allows simultaneous determination of gene distances and order for three genes.
To perform a three-point test cross, what are the genotypes of the two parental individuals that are crossed?
a) Two homozygous dominant individuals.
b) A double heterozygote and a single homozygote recessive.
c) A triple heterozygote and a triple homozygous recessive.
d) Two triple homozygous recessive individuals.
e) A single heterozygote and a single homozygous dominant.
c) A triple heterozygote and a triple homozygous recessive.
