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1. What are the four types of nucleotides that make up DNA and how do
they pair up to form the double helix? (2 points)
Answer: The four types of nucleotides are adenine (A), thymine (T),
cytosine (C), and guanine (G). They pair up according to the
complementary base pairing rule: A with T and C with G. The two strands
of DNA are held together by hydrogen bonds between the paired bases.
Rationale: This question tests the basic knowledge of the structure and
composition of DNA, which is the main genetic material in humans.
2. What is the difference between a gene and an allele? (2 points)
Answer: A gene is a segment of DNA that codes for a specific protein or
trait. An allele is a variant form of a gene that may have different effects
on the phenotype. For example, the gene for blood type has three alleles:
A, B, and O.
Rationale: This question tests the understanding of the concepts of gene
and allele, which are important for studying inheritance and variation.
3. What is the difference between genotype and phenotype? (2 points)
Answer: Genotype is the genetic makeup of an individual, which
determines the potential traits that can be expressed. Phenotype is the
physical appearance or expression of the traits, which may be
influenced by environmental factors. For example, a person may have the
genotype for brown eyes (BB) but have blue eyes as a phenotype due to aÂÂ
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