MCQ ON CYTOGENETICS PART 4

MCQ ON CYTOGENETICS PART 4

This part of MCQs is based on chromosome and Sex Determination in Drosophila, mammals and others, sex linked inheritance, dosage compensation, sex influenced and sex limited traits.

1. Which mode of sex determination is found in Drosophila?
(a) XX /XY
(b) XX/ XO
(c) ZZ/ ZW
(d) MM/NN
Ans. (a) XX /XY

2. Choose the true statement for Drosophila sex determination?
(a) Males are produced by presence of Y chromosome
(b) Females are produced by presence of Y chromosome
(c) Two X chromosome will always produce a female
(d) Two Y chromosome will always produce a male
Ans. (c) Two X chromosome will always produce a female
Explanation: In Drosophila the sex is determined by the sex chromosome: set of autosome ratio.

Read… TYPES OF CHROMOSOME-STRUCTURE&DEFINITION

3. Which of these genes is responsible for the development of sex of Drosophila?
(a) Xce
(b) Xist
(c) XIC
(d) Sxl or sex lethal gene
Ans. (d) Sxl or sex lethal gene

4. Sxl directly affects _____________
(a) SR
(b) Dsx
(c) Tra
(d) Xce
Ans. (c) Tra
Explanation: Sxl directly affects the splicing of tra pre-mRNA and produces a functional gene when Sxl is turned on.

5. The Sxl gene is turned ____________ by a ratio of _____________for X:A.
(a) OFF, 1
(b) OFF, 0.5
(c) ON, 0.5
(d) ON, 0.75
Ans. (b) OFF, 0.5
Explanation: The Sxl gene is turned ON only when the ratio of X: A is 1, other times it is OFF. An OFF state produces a male while on state produces a female.

6. Drosophila melanogaster remains one of the most commonly used model organisms for biomedical science. Which of the following reason made it indispensable for basic research?
(a) Low cost
(b) Rapid generation time
(c) Excellent genetic tools
(d) All of the above
Ans. (d) All of the above

7. Which of the following is a default pathway in Drosophila?
(a) Development of male characters
(b) Repression of male characters
(c) Development of female characters
(d) All pathways are induced
Ans. (a) Development of male characters

8. Which of the following will give a normal female Drosophila?
(a) AAA + XX
(b) AA + XXY
(c) AA + XY
(d) AA + XXX
Ans. (b) AA + XXY
Explanation: In the following case the X: A ratio is 1 which is required for developing female characters. In all the other cases viable female is not produced.

9. The XO system of sex determination is found in ______________
(a) Insects
(b) Birds
(c) Reptiles
(d) Mammals
Ans. (a) Insects

10. In XO system a male has a mother but not a _____________
(a) Grandfather
(b) Grandmother
(c) Father
(d) Sibling
Ans. (c) Father
Explanation: The males are produced by parthenogenesis (mitosis). While fertilization only takes place in case of a female child, only the two X chromosomes come together. Thus, the male has a mother but no father; they do however have a grandfather.

Read… APOMIXIS POLYEMBRYONY AND PARTHENOCERPY

11. In case of XO system if an organism has AA+XO it will be a _______
(a) Male
(b) Neuter
(c) Female
(d) Bisexual
Ans. (a) Male

12. Genic system of sex determination is seen in _______________
(a) Yeast
(b) Fishes
(c) Reptiles
(d) Mammals
Ans. (a) Yeast

13. Which of the following is true for a genic mode of sex determination?
(a) It is seen in higher eukaryotes
(b) Gene locus determines gender
(c) XX will always give female in this case
(d) It makes use of parthenogenesis for producing male offspring
Ans. (b) Gene locus determines gender
Explanation: Genic mode of sex determination is seen in eukaryotic microorganisms. In this case, there is no separate chromosome but allele at the gene locus determines sex.

14. In yeast the gene responsible for sex determination is ______________
(a) SXL
(b) XCE
(c) MAT
(d) XIST
Ans. (c) MAT

15. In bees the males are produced by _________
(a) Mitosis and then fertilization
(b) Meiosis and then fertilization
(c) Mitosis but no fertilization
(d) Meiosis but no fertilization
Ans. (c) Mitosis but no fertilization
Explanation: Bees have XO system of sex determination. Here the males are produced by parthenogenesis (mitosis) occurring in the mother that gives the zygote for male offspring.

Read… MITOSIS & MEIOSIS- CELL DIVISION

16. Which of the following sex determination is found in Mammals?
(a) XX/ XY
(b) XX/ XO
(c) ZZ/ ZY
(d) Genic
Ans. (a) XX/ XY

17. In mammals which of the following will be a Turner?
(a) AA + XXY
(b) AA+ XYY
(c) AA + XO/ XY
(d) AA+ XO
Ans. (d) AA+ XO

18. The gene for sex determination in mammals is _________ and it is located in ___________
(a) MAT, Y
(b) SRY, Y
(c) MAT, X
(d) SRY, X
Ans. (b) SRY, Y

19. Humans and most other mammals have two sex chromosomes, X and Y, that in combination determine the sex of an individual. Females have two X chromosomes in their cells, while males have?
(a) One X and one Y
(b) Two X and one Y
(c) Two X
(d) All of these
Ans. (a) One X and one Y

20. Which of the following is wrong for sex chromosome?
(a) X chromosome is larger than Y
(b) Female human are homozygous
(c) Y chromosome carries TDF
(d) All genes present on Y chromosome are unique to it
Ans. (d) All genes present on Y chromosome are unique to it

21. Klinefelter syndrome results due to ____________
(a) Non-disjunction in the male gamete
(b) Non-disjunction in the female gamete
(c) Gradual loss of chromosome
(d) Non-disjunction in either male or female gamete
Ans. (d) Non-disjunction in either male or female gamete

22. The intersex is produced by ________________
(a) Fusion of a male and female zygote
(b) Loss of X chromosome from some cells
(c) Loss of Y chromosomes from some cells
(d) Gain of X or Y chromosome due to non-disjunction
Ans. (c) Loss of Y chromosomes from some cells

23. Genes which are present in the homologous region of X and Y chromosomes are called______________
(a) Autosomal
(b) Sex linked
(c) Partially sex linked
(d) Unlinked
Ans. (c) Partially sex linked

24. Choose the odd one out.
(a) Faulty tooth enamel
(b) Haemophilia
(c) Duchenne muscular dystrophy
(d) Color blindness
Ans. (a) Faulty tooth enamel
Explanation: Except faulty tooth enamel which is a dominant trait all three diseases are X linked recessive diseases.

25. A colorblind mother and a normal father give birth to a Klinefelter child with normal vision. Where do you think the non-disjunction has taken place?
(a) 1st meiotic division of mother
(b) 2nd meiotic division of the father
(c) 2nd meiotic division of mother
(d) 1st meiotic division of father
Ans. (d) 1st meiotic division of father
Explanation: Since the child was not color blind, the non-disjunction must be in the male parent. This is possible only if one X chromosome was normal which here came from father. Also as the disjunction produced XY and not two copies of same chromosome it must have been in 1st division.

26. If colorblindness was a dominant trait, which of the following would not be true?
(a) It would be expressed in heterozygous females
(b) It would be expressed in males
(c) It would never be turned off
(d) It would not skip generations
Ans. (c) It would never be turned off

27. What is the probability that the son of a color blind father would be color blind?
(a) 0
(b) 1/4
(c) 1/2
(d) 1
Ans. (a) 0
Explanation: Sons get the Y chromosome from father and the X from mother. So unless the mother is also a carrier, there is no probability of the son being colorblind.

28. Y linked inheritance is _______________ inheritance.
(a) Criss cross
(b) Jumping
(c) Loop
(d) Straight
Ans. (d) Straight
Explanation: The inheritance pattern of Y linked gene is straight as it moves from father to son. Only males can inherit these traits.

29. Which of the following is a Y linked gene?
(a) Faulty dental enamel
(b) Haemophilia
(c) Hypertrichosis
(d) Phenyl ketone urea
Ans. (c) Hypertrichosis (It is the presence of hair in the ear)

30. A turner child born to normal parents is haemophilic. Where did the non-disjunction occur?
(a) Mother
(b) Father
(c) Zygote
(d) Grand mother
Ans. (b) Father
Explanation: The only possibility here is that the mother was a carrier. The egg received this defective X chromosome from mother and no sex chromosome from the father. Thus, there was non disjunction in the father.

31. Which of the following is partially sex linked?
(a) Faulty tooth enamel
(b) Hypertrichosis
(c) Complete colorblindness
(d) Haemophilia
Ans. (c) Complete colorblindness

32. Dosage compensation y inactivation of one X chromosome is seen in ___________________
(a) Mammals
(b) Drosophila
(c) Metaphase
(d) Telophase
Ans. (b) Drosophila

33. The inactivated X chromosome in female forms a highly condensed structure called the Barr body. Barr bodies are found in the………….
(a) cytoplasm of female
(b) cytoplasm of male
(c) nuclei of female
(d) nuclei of male
Ans. (c) nuclei of female

34. In female one of the two X chromosomes in somatic cells gets condensed and forms the Barr body Lyonisation. It takes place ____________
(a) 7th day after fertilization
(b) 15th day after fertilization
(c) 1st month after fertilization
(d) 6th month after fertilization
Ans. (b) 15th day after fertilization

35. Which of the following determines which X chromosome remains active?
(a) XIST
(b) XIC
(c) XCE
(d) RB
Ans. (c) XCE

36. Which one of the following is the only active gene in the inactivated X chromosome?
(a) XIST
(b) XCE
(c) Histone coding gene
(d) Ribosomal gene
Ans. (a) XIST

37. Which one of the following is true for Drosophila?
(a) They don’t have X chromosome
(b) One of the female X chromosome is inactivated
(c) The male Y chromosome is inactivated
(d) The male X chromosome is hyper active
Ans. (d) The male X chromosome is hyper active

38. Sex influenced traits are only related to?
(a) Male
(b) Female
(c) Male & Female
(d) can’t be said
Ans. (c) Male & Female

39. The sex influenced traits are present in _______________________
(a) Autosome
(b) Sex chromosome
(c) Mitochondrial chromosome
(d) These are epigenetic traits
Ans. (a) Autosome

40. If A is a sex influenced trait that is more expressed in males, then which of the following is false?
(a) Only male having a homozygous recessive form of this gene will not express it
(b) No female will express the gene
(c) The gene is autosomal
(d) Heterozygous female will not express this gene
Ans. (b) No female will express the gene

41. What will be the phenotype and genotype of a daughter born to bald mother and non-bald father?
(a) b+/b+ non-bald
(b) b+/b+ bald
(c) b/b+ non-bald
(d) b/b+ bald
Ans. (c) b/b+ non-bald
Explanation: Baldness is a dominant gene for a male. A bald mother is thus homozygous for the allele; at least one baldness gene will thus pass to offspring from her. The father is normal so he must lack any baldness allele and a normal gene will pass from him. Hence daughter is a heterozygote and normal.

Read… DIFFERENCE BETWEEN GENE AND ALLELE

42. Appearance of cock feather in chicken is ________________
(a) X linked
(b) Y linked
(c) Sex influenced
(d) Sex limited
Ans. (d) Sex limited

See also…
MCQ ON CYTOGENETICS PART1
MCQ ON CYTOGENETICS PART 2
MCQ ON CYTOGENETICS PART 3