GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Inheritance
Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology
All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #2 : Help With Other Inheritance Patterns
When the expression and subsequent phenotype of one gene is dependent on the expression of another gene, this type of phenonemon is known as __________.
codominance
gene masking
complete dominance
epistasis
incomplete dominance
epistasis
The correct answer is epistasis. Complete dominance, codominance, and incomplete dominance describe the expression of only one gene (one set of alleles) that do not depend on the expression of other genes. Gene masking is not a phenomenon in genetics.
Example Question #3 : Help With Other Inheritance Patterns
Each of the listed statements about transposable genetic elements in eukaryotic genomes are true except for which one?
Found in clusters within the genome
Activity is repressed by small RNAs that are transcribed by RNA polymerase II and III
Can introduce genetic mutations through creating inversions
Converted to RNA intermediate by transposase proteins
Converted to RNA intermediate by transposase proteins
Transposable elements are divided into two categories: Type 1 (retrotransposons), which form RNA intermediates, and type 2 (transposons), which do not form RNA intermediates and directly enter a new site. Transposase proteins regulate the translocation of type 2 transposable elements, which do not require a RNA intermediate.
Example Question #4 : Help With Other Inheritance Patterns
Crossing foxes that are double heterozygotes for two genes regulating coat color yields 27 grey, 12 red and 9 black offspring. What mechanism explains the ratio of coat color observed in the offspring?
Mendelian inheritance
Epistasis
Pleiotropy
X-chromosome linked
Chromosomal linkage
Epistasis
If this were a Mendelian trait, we would expect a 9:3:3:1 ratio of offspring coat color. However, the results show a 9:4:3 ratio. Epistatic interaction between genes can be identified by one gene masking the phenotype of another gene. In this case, the double homozygote phenotype was masked by the red coat color phenotype (4 offspring, instead of seeing 3 red offspring). This suggests that the two coat color genes are epistatic.
Example Question #33 : Molecular Biology And Genetics
A student determines that color for a new diploid species is conferred by one gene. The student mates a homozygous dominant red mother with a homozygous recessive green father to yeild 100% of offspring that are both red and green. What form of inheritance best describes this?
Polygenic trait
Epistasis
Incomplete dominance
Complete dominance
Codominance
Codominance
The correct answer is codominance. According to this mode of inheritance, individuals that are heterozygous for a condition express both alleles equally. If the offspring were exhibited incomplete dominance, their phenotype would have been a red-green blend because the heterozygous condition is a blend of both alleles. Complete dominance occurs when the heterozygous condition exhibits the same phenotype as the homozygous dominant. In epistasis, the expression of one gene is dependent on the expression of a second, which is a form of inheritance that does not apply to this question. Finally, a polygenic trait is a trait that is conferred by multiple genes, a situation for which we know is not the case in this question.
Example Question #6 : Help With Other Inheritance Patterns
Human beings are capable of having A, B, AB or O blood. While "A" and "B" alleles can be expressed at the same time on red blood cells, O type blood can only be a phenotype if a person has 2 "O" alleles.
Based on this information, what two modes of inheritance contribute to blood type in human beings?
Codominance and sex-linked dominance
Complete dominance and incomplete dominance
Codominance and incomplete dominance
Codominance and complete dominance
Codominance and complete dominance
Since A and B can be expressed at the same time on a red blood cell, we can say that A and B are codominant to one another. On the other hand, this cannot be said for the O allele. If a person has an A allele and an O allele, that person will have type A blood. Both A and B are dominant over O. As a result, we also see complete dominance take place with blood types. To help solidify this concept, added below is a genotype/phentoype comparison:
A/A = A blood
A/O = A blood
O/O = O blood
B/B = B blood
B/O = B blood
A/B = AB blood
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All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
