CBSE Class 10 Science Case Study Questions Heredity and Evolution MCQs

Case/Passage – 1
Question. A person first crossed pure-breed pea plants having roundyellow seeds with pure-breed pea plants having wrinkledgreen seeds and found that only A-B type of seeds were produced in the F1 generation. When F1 generation pea plants having A-B type of seeds were cross-breed by selfpollination, then in addition to the original round-yellow and wrinkled-green seeds, two new varieties A-D and C-B type of seeds were also obtained.
(a) What are A-B type of seeds?
(b) State whether A and B are dominant traits or recessive traits.
(c) What are A-D type of seeds?
(d) What are C-B type of seeds?
(e) Out of A-B and A-D types of seeds, which one will be produced in (i) minimum numbers, and (ii) maximum numbers, in the F2 generation?
Answer: (a) Round yellow
(b) A (round) and B (yellow) are dominant traits
(c) Round-green
(d) Wrinkled-yellow
(e) (i) A–D (ii) A–B

Question. Question number (a) – (d) are based on the images (A) and (B) given below. Study them and answer the following questions.  

(a) What term can be used for the structure given in image A?
(b) What term can be used for the structure given in image B?
(c) Which image shows a common ancestry? 
(d) Which image has a common function but different origin?   
Answer: (a) Homologous organs
(b) Analogous organs
(c) Image A shows common ancestry
(d) Image B i.e., analogous organs have a different origin but common functions.

Case/Passage – 2
Most human chromosomes have a maternal and a paternal copy, and we have 22 such pairs. But one pair, called the sex chromosomes, is odd in not always being a perfect pair. Women have a perfect pair of sex chromosomes, both called X. But men have a mismatched pair in which one is a normal-sized X while the other is a short one called Y. So women are XX, while men are XY

Question. If a normal cell of human body contains 46 pairs of chromosomes then the numbers of chromosomes in a sex cell of a human being is most likely to be:
(a) 60
(b) 23
(c) 22
(d) 40   

Answer: B

Question. The process where characteristics are transmitted from parent to offsprings is called:
(a) Variation
(b) Heredity
(c) Gene
(d) Allele
(e) None of the above   

Answer: B

Question. In human males, all the chromosomes are paired perfectly except one. These unpaired chromosomes are:
(a) Large chromosome
(b) Small chromosome
(c) Y chromosome
(d) X chromosome 

Answer: C

Question. Which of the following determines the sex of a child?
(a) The length of the mother’s pregnancy
(b) The length of time between ovulation and copulation
(c) The presence of an X chromosome in an ovum
(d) The presence of a Y chromosome in a sperm 

Answer: D

Question. Who have a perfect pair of sex chromosomes?
(a) Girls only
(b) Boys only
(c) Both girls and boys
(d) It depends on many other factors   

Answer: A

Case/Passage – 3
In some animals, the temperature at which fertilised eggs are kept determines whether the animal developing in the egg will be male or female. In other animals, such as snails, individuals can change sex, that is sex is not genetically determined. In human beings, sex of individuals is largely genetically determined. All chromosomes in human beings are not paired. We have 22 pairs and one pair of sex chromosomes which is odd and not always a perfect pair.

Question. Who is responsible for birth of male child?
(a) Father
(b) Mother
(c) Father only in first pregnancy.
(d) Mother only in first pregnancy

Answer: A

Question. How many pairs of chromosomes are called autosomes?
(a) 23
(b) 22
(c) 21
(d) 20

Answer: B

Question. Which pair of chromosomes are present in Male
(a) XX
(b) YY
(c) XY
(d) XXY

Answer: C

Question. Which of the following statement is true?
(a) Men have short sized X chromosome
(b) Men have one long sized Y chromosome
(c) Men have normal sized Y chromosome
(d) Men have one short sized Y chromosome

Answer: D

Question. Which pair of chromosomes are present in female?
(a) XX
(b) YY
(c) XY
(d) XXY

Answer: A