Practice Questions
Examine the chromosomal composition of individuals with Turner's Syndrome and Klinefelter's Syndrome and state the key difference.
Compare the genetic makeup of a pea plant that is homozygous for tallness with one that is heterozygous for tallness, using appropriate symbols.
A diploid organism is heterozygous for 5 different gene loci. Calculate the total number of different types of gametes this organism can produce, assuming all loci assort independently.
Define a 'monohybrid cross'.
Critique the societal practice of blaming women for the sex of their children, based on the mechanism of sex determination in humans.
Name the scientist who is known as the father of genetics and conducted experiments on pea plants.
Define the term 'allele'.
Name the genetic disorder that is caused by the presence of an additional copy of chromosome 21.
Justify why Turner's syndrome (45, XO) is classified as a monosomy, whereas Klinefelter's syndrome (47, XXY) is classified as a trisomy.
Contrast the phenotypic expression in the generation for incomplete dominance and co-dominance using one example for each.
Define a test cross and explain its primary purpose in genetics.
Demonstrate how a test cross can be used to determine whether a pea plant with a dominant phenotype (e.g., violet flowers) is homozygous (VV) or heterozygous (Vv).
Compare the genetic mechanism of sex determination in humans with that in birds, highlighting which sex is heterogametic in each case.
Explain the mechanism of sex determination in human beings.
Critique the statement: 'Mendel's Law of Independent Assortment is a fundamental principle that applies to all genes in sexually reproducing organisms.' Justify your position with a specific example.
A couple, where the man has blood group A and the woman has blood group B, have a child with blood group O. Propose the genotypes of the parents and the child that make this outcome genetically possible.
Evaluate the concept of dominance using the example of starch synthesis in pea seeds. Justify why dominance is not an autonomous feature of a gene but depends on the phenotype being examined.
Explain the Law of Dominance using an example from Mendel's experiments.
Critique the historical term 'blending inheritance' to describe the pink-flowered F1 progeny in snapdragons (Antirrhinum sp.). Justify your critique with evidence from the F2 generation.
A woman who is a carrier for the sex-linked recessive trait of haemophilia () marries a man with normal blood clotting (). Calculate the probability of them having: (a) a haemophilic son, and (b) a carrier daughter.
Explain the concept of incomplete dominance with the example of flower colour in the Snapdragon plant.
In pea plants, tall (T) is dominant to dwarf (t). Using a Punnett square, demonstrate the expected genotypic and phenotypic ratios of the offspring from a cross between a heterozygous tall plant (Tt) and a dwarf plant (tt).
Apply the concept of pleiotropy to analyze why a single gene mutation causes multiple phenotypic effects in the disease phenylketonuria (PKU).
List the seven pairs of contrasting traits in pea plants studied by Gregor Mendel.
A child has blood group O. His father has blood group A and his mother has blood group B. Analyze this information to determine the genotypes of the parents and calculate the probability of their next child having blood group AB.
Identify the genotypic ratio obtained in the generation of a Mendelian monohybrid cross.
Compare and contrast Mendel's Law of Segregation with his Law of Independent Assortment. Analyze a situation where the Law of Independent Assortment would not apply.
Design an experimental strategy using a series of crosses to determine if a newly discovered flower color trait (e.g., blue) in a pea plant is dominant or recessive, and to subsequently confirm the genotype of the blue-flowered parent plant.
Evaluate the genetic basis of sickle-cell anaemia as an example of a point mutation that also provides a selective advantage in certain environments.
Describe the difference between 'genotype' and 'phenotype'.
Propose a reason why chromosomal disorders like Down's syndrome are typically sporadic events and are not considered 'inherited' in the same pattern as Mendelian disorders like haemophilia.
Explain the concept of co-dominance using the example of ABO blood grouping in humans.
You are given two tall pea plants of unknown genetic makeup. Design a single, definitive experiment to determine the genotype of each plant. Illustrate the possible outcomes with Punnett squares and explain how you would interpret the results.
In a dihybrid cross in Drosophila involving genes for body color and wing size, the F2 phenotypic ratio observed is 70% parental types and 30% recombinant types, which deviates from the expected 9:3:3:1 ratio. Create a hypothesis to explain this result and propose a method to map the relative distance between these two genes.
When Mendel crossed a tall plant with yellow seeds (TtYy) with a tall plant with green seeds (Ttyy), what proportion of the offspring would be expected to be (a) tall and green, and (b) dwarf and green? Solve using a Punnett Square.
Describe Phenylketonuria and Sickle-cell anaemia as examples of Mendelian disorders.
In a dihybrid cross in Drosophila, the recombination frequency between genes for yellow body (y) and white eyes (w) is found to be . Analyze how this result demonstrates gene linkage and contrast it with the expected outcome from Mendel's Law of Independent Assortment.
Examine the provided pedigree chart for an autosomal recessive trait. Analyze the chart to determine the genotype of individuals II-3 and II-4, assuming the trait is sickle-cell anaemia ( for normal, for sickle-cell). Provide a justification for your answer.
A man with normal vision, whose father was colour-blind, marries a woman who is a carrier for colour blindness. Analyze the genotypes and calculate the probability of their first child being a colour-blind son.
Propose a genetic explanation for the observation that a male honeybee (drone) has a grandfather and can have grandsons, but cannot have a father or sons.
Summarize the key findings of Mendel's monohybrid cross experiment involving tall (TT) and dwarf (tt) pea plants through the generation.
Describe the Chromosomal Theory of Inheritance and name the scientists who proposed it.
Formulate a long-term breeding program for a farmer who wants to develop a new cattle breed that combines high milk yield (a polygenic trait) with resistance to a specific disease (controlled by a single dominant allele, R).
A student wants to create a true-breeding line of dwarf pea plants with wrinkled seeds from a heterozygous parent plant with genotype TtRr (Tall, Round). Formulate a multi-generational breeding plan to achieve this goal, justifying each step with Punnett squares.
Design a pedigree chart for a family over three generations to illustrate the inheritance of an X-linked recessive disorder like colour blindness. The first-generation female is a carrier, and her partner is unaffected. Propose the genotypes for all individuals.