Genetic variation：練習問題

If an individual has two different alleles for a particular gene, which term best describes their genotype?

A scientist is studying a specific trait in a population that is controlled by a single gene with two alleles. If an individual is heterozygous for this trait, what must be true about their genotype and phenotype?

A specific genetic disorder is mentioned in the OxfordAQA syllabus as being caused by the presence of an extra chromosome. Which condition matches this description, and what is the total number of chromosomes typically found in a body cell of an affected human?

In a certain species of plant, the allele for red flowers (R) is dominant over the allele for white flowers (r). If two heterozygous (Rr) plants are crossed, what is the expected percentage of offspring with white flowers?

Differences in the characteristics of individuals can be caused by genes, the environment, or both. Which of the following best describes genetic variation as defined in the OxfordAQA syllabus?

A scientist notes that a group of plants are all genetically identical but show different heights when grown in different soil types. Suggest why this variation is likely caused by environmental factors.

If an individual is heterozygous for a specific gene, explain why only the dominant allele is expressed in their phenotype while the recessive allele remains hidden.

In a population of insects, a mutation occurs in the DNA of a reproductive cell. Explain why this specific change is considered a cause of genetic variation in the offspring.

In humans, the allele for polydactyly (having extra fingers or toes) is dominant (\(D\)) and the allele for the normal number of digits is recessive (\(d\)).

a) A man who is heterozygous for polydactyly and a woman who has a normal number of digits plan to have a child. Construct a genetic diagram or Punnett square to show the possible genotypes of their offspring.
b) Based on your diagram, what is the probability that their child will inherit polydactyly? Express your answer as a percentage.