Heredity and variation：練習問題

Which of the following best describes the characteristics of discontinuous variation in a human population?

A woman with blood group A and a man with blood group B have a child with blood group O. Based on this observation, what is the most likely genetic explanation for the parents, and which type of variation does human blood group represent?

A couple already has four sons. What is the probability that their fifth child will be a girl, and which sex chromosome provided by which parent determines the sex of the child?

Which of the following is the best scientific definition of variation as it relates to a group of humans?

In humans, a normal body cell contains \( 46 \) chromosomes. How many chromosomes are present in a zygote and a human sperm cell respectively?

Apart from heredity, identify the other major factor that determines variations between individuals.

Consider a pair of human identical twins who were separated at birth and raised in environments with significantly different levels of ultraviolet (UV) radiation and nutritional standards. Years later, it is observed that they have different skin tones and body masses, yet their ABO blood groups remain exactly the same.

Based on the unifying concept of variation, explain why their blood groups are identical while their skin tones differ.

According to the curriculum, variations between individuals in a population are determined by heredity and which other factor?

A group of students conducted a survey on the heights of 100 individuals in their school. They plotted the collected data on a histogram and observed a bell-shaped curve.

(a) Identify the type of variation shown by height in this population. (1 point)

(b) Based on the curriculum, variations between individuals are determined by two main factors. Identify these two factors. (2 points)

(c) Apart from height, suggest one other example of this type of variation in humans. (1 point)

(d) If the students were to survey blood groups instead, would they obtain the same bell-shaped curve? Explain your answer briefly by naming the type of variation blood group belongs to. (2 points)

A pair of identical twins, Caleb and Joshua, were separated at age 5. Caleb moved to a tropical island where he spent much of his time swimming outdoors and consuming a high-protein diet. Joshua moved to a cold, high-altitude city where he stayed indoors most of the time and had a different diet. At age 25, they were reunited for a medical study.

(a) State the total number of chromosomes found in a normal liver cell of Joshua. (1 point)

(b) The study found that Caleb's skin was significantly darker than Joshua's. Explain this difference by referencing the two main factors that determine variation in individuals. (2 points)

(c) Caleb and Joshua both belong to blood group B. Explain why their blood groups are identical while their skin tones are different. (2 points)

(d) If a segment of Joshua's double-stranded DNA contains 24% Guanine (G), calculate the percentage of Thymine (T) in that same segment. (2 points)