NEET UG - Chromosomal basis of inheritance - linkage crossing over, sex determination Online Test (MCQ Quiz)

1. Who is credited with proposing the chromosomal theory of inheritance?

A) Gregor Mendel B) Thomas Hunt Morgan C) Sutton and Boveri D) Alfred Sturtevant

2. Which organism did Thomas Hunt Morgan primarily use for his experiments on linkage and crossing over?

A) Escherichia coli B) Drosophila melanogaster C) Zea mays D) Saccharomyces cerevisiae

3. Linkage refers to the tendency of genes located on the same chromosome to:

A) Segregate independently B) Be inherited together C) Undergo mutation frequently D) Recombine during meiosis

4. The phenomenon where alleles of different genes segregate independently during gamete formation is known as:

A) Linkage B) Crossing over C) Independent assortment D) Gene flow

5. Crossing over occurs during which stage of meiosis?

A) Leptotene B) Zygotene C) Pachytene D) Diplotene

6. The physical exchange of genetic material between non-sister chromatids of homologous chromosomes is called:

A) Synapsis B) Chiasma formation C) Crossing over D) Segregation

7. A chiasma (plural: chiasmata) is the visible manifestation of:

A) Chromosome duplication B) Homologous chromosome pairing C) Crossing over events D) Centromere division

8. The frequency of crossing over between two genes on the same chromosome is proportional to:

A) Their physical distance B) Their molecular weight C) The number of alleles present D) The ploidy level of the organism

9. Who developed the concept of gene mapping based on recombination frequencies?

A) Thomas Hunt Morgan B) Alfred Sturtevant C) Sutton and Boveri D) Barbara McClintock

10. A genetic map represents the relative positions of genes on a chromosome, with distances measured in:

A) Micrometers B) Base pairs C) Centimorgans (cM) or map units D) Megabases

11. If the recombination frequency between two genes is 10%, it means they are approximately how many map units apart?

A) 1 map unit B) 5 map units C) 10 map units D) 20 map units

12. What is the maximum recombination frequency observed between two linked genes?

A) 25% B) 50% C) 75% D) 100%

13. Genes that are very far apart on the same chromosome behave as if they are:

A) Strongly linked B) Unlinked and assort independently C) Located on different chromosomes D) Subject to chromosomal aberrations

14. In Drosophila, sex is determined by:

A) The presence of a Y chromosome B) The ratio of X chromosomes to autosomes C) The number of autosomes D) Hormonal factors only

15. In humans, sex determination is primarily based on:

A) The number of X chromosomes B) The presence of a Y chromosome C) The ratio of X chromosomes to autosomes D) Environmental factors

16. Which chromosome is considered the male-determining chromosome in humans?

A) X chromosome B) Y chromosome C) Autosome 1 D) Autosome 2

17. An individual with a karyotype of XXY in humans is typically:

A) Male with Klinefelter syndrome B) Female with Turner syndrome C) Male with Down syndrome D) Female with Triple X syndrome

18. An individual with a karyotype of XO in humans is typically:

A) Male with Klinefelter syndrome B) Female with Turner syndrome C) Male with Noonan syndrome D) Female with Swyer syndrome

19. The presence of the SRY gene on the Y chromosome is crucial for:

A) Female sex determination B) Male sex determination C) X chromosome inactivation D) Autosomal gene expression

20. In birds, sex determination is of the ZW type. Which sex is heterogametic?

A) Males (ZZ) B) Females (ZW) C) Both sexes are homogametic D) Sex is determined by environmental factors

21. In the ZW sex determination system, which sex has two different sex chromosomes?

A) ZZ (male) B) ZW (female) C) WW (hypothetical) D) ZO (hypothetical)

22. What is the term for genes located on the sex chromosomes?

A) Autosomal genes B) Sex-linked genes C) Mitochondrial genes D) Plastid genes

23. X-linked recessive traits are more commonly observed in which sex?

A) Males B) Females C) Both sexes equally D) Neither sex

24. Why are X-linked recessive traits more common in males?

A) Females have two X chromosomes to mask the recessive allele. B) Males have two Y chromosomes that express the trait. C) Females have a higher mutation rate. D) Males have a shorter generation time.

25. Color blindness is a classic example of which type of inheritance?

A) Autosomal dominant B) Autosomal recessive C) X-linked recessive D) Y-linked

26. Hemophilia is another well-known example of:

A) Autosomal dominant inheritance B) Autosomal recessive inheritance C) X-linked recessive inheritance D) Mitochondrial inheritance

27. A male with a normal genotype for color vision (X^B Y) and a female carrier (X^B X^b) have children. What is the probability of their son being color blind?

A) 0% B) 25% C) 50% D) 100%

28. Which of the following is a Y-linked trait in humans?

A) Red-green color blindness B) Hemophilia C) Duchenne muscular dystrophy D) Hairy ears (Hypertrichosis)

29. Genes located on the Y chromosome are passed directly from:

A) Mother to daughter B) Father to son C) Mother to son D) Father to daughter

30. When crossing over occurs between two linked genes, what is the result?

A) Parental gametes only B) Recombinant gametes only C) Both parental and recombinant gametes D) No gametes are formed

31. A test cross involving a heterozygous individual for two linked genes would reveal:

A) The genotype of the individual B) The presence of parental and recombinant offspring C) The linkage phase of the alleles D) All of the above

32. The phenomenon of 'interference' in crossing over refers to:

A) The occurrence of crossing over B) The complete absence of crossing over C) The effect of one crossover event on the likelihood of another crossover nearby D) The independent assortment of genes

33. If interference is positive, it means that:

A) The occurrence of one crossover increases the chance of another nearby. B) The occurrence of one crossover decreases the chance of another nearby. C) The occurrence of one crossover has no effect on another. D) Crossing over is completely absent.

34. Coefficient of coincidence (C.O.C.) is calculated as:

A) Observed recombination frequency / Expected recombination frequency B) Expected recombination frequency / Observed recombination frequency C) Observed double crossovers / Expected double crossovers D) Expected double crossovers / Observed double crossovers

35. Interference (I) is related to the Coefficient of Coincidence (C.O.C.) by the formula:

A) I = 1 - C.O.C. B) I = C.O.C. - 1 C) I = 1 + C.O.C. D) I = C.O.C. / 1

36. In species with XY sex determination, the X chromosome contains many more genes than the Y chromosome. These genes are called:

A) Y-linked genes B) Autosomal genes C) X-linked genes D) Pseudoautosomal genes

37. Pseudoautosomal regions (PARs) are found on:

A) Autosomes only B) The Y chromosome only C) Both X and Y chromosomes D) Mitochondrial DNA

38. Genes located in pseudoautosomal regions show inheritance patterns similar to:

A) Autosomal genes B) Y-linked genes C) X-linked recessive genes D) X-linked dominant genes

39. In the fruit fly Drosophila, sex is determined by the X:autosome ratio. A fly with XXAA (where A represents a set of autosomes) would be:

A) Male B) Female C) Intersex D) Supermale

40. A fruit fly with XAAA (where X is one X chromosome and A represents a set of autosomes) would be:

A) Male B) Female C) Intersex D) Superfemale

41. The phenomenon where a single gene controls multiple phenotypic traits is known as:

A) Epistasis B) Pleiotropy C) Codominance D) Incomplete dominance

42. Which of the following is an example of pleiotropy?

A) ABO blood groups B) Sickle cell anemia C) Flower color in peas D) Skin color in humans

43. The chromosomal theory of inheritance was independently proposed by:

A) Morgan and Sturtevant B) Sutton and Boveri C) Mendel and Darwin D) Watson and Crick

44. Which term describes genes located on the same chromosome that are inherited together?

A) Independent assortment B) Linkage C) Segregation D) Epistasis

45. The specific points on homologous chromosomes where crossing over occurs are called:

A) Centromeres B) Telomeres C) Chiasmata D) Kinetochores

46. In humans, the absence of the SRY gene on the Y chromosome leads to the development of:

A) Male characteristics B) Female characteristics C) Intersex characteristics D) No significant developmental difference

47. What is the Barr body?

A) An inactivated X chromosome in female mammals B) An inactivated Y chromosome in male mammals C) A duplicated chromosome during mitosis D) A homologous chromosome pair during meiosis

48. The phenomenon of X-chromosome inactivation in female mammals is an example of:

A) Gene amplification B) Gene deletion C) Dosage compensation D) Translocation

49. A three-point cross is used to determine:

A) The linkage between two genes B) The order and relative distances of three linked genes C) The frequency of independent assortment D) The presence of sex-linked traits

Chromosomal basis of inheritance - linkage crossing over, sex determination - Online Test

Test Results