This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Cellular Reproduction – Meiosis”.
1. Meiosis ensures the production of a haploid phase.
Explanation: Meiosis ensures a haploid phase in the life cycle and leads to a reduction in the genetic material. Fertilization ensures a diploid phase and leads to doubling of the chromosomal content.
2. One round of meiotic division gives rise to _____ haploid cells.
Explanation: One round of meiotic division gives rise to 4 haploid cells. In the process of meiosis, there are two sequential rounds of division without an intervening round of replication.
3. A highly specialized sperm cell is also called ________________
Explanation: A highly specialized sperm cell – spermatozoon results from complex differentiation of the spermatid. The spermatogonia undergo meiosis to become primary spermatocytes, which then undergo two divisions of meiosis to produce four spermatids.
4. Vertebrate eggs are typically fertilized before ___________________ is complete.
Explanation: Vertebrate eggs typically fertilize at a stage before the completion of meiosis, usually the metaphase II. Meiosis is completed after fertilization, when sperm is already residing in the egg.
5. Zygotic meiosis only occurs in _______________________
Explanation: Zygotic meiosis or initial meiosis occurs only in protists and fungi. In these organisms the meiotic divisions occur just after fertilization to facilitate the production of spores.
6. The sporic or intermediate meiosis is unrelated to gamete formation.
Explanation: The sporic or intermediate meiosis occurs in plants and some algae. In these organisms, the meiotic division takes place at a stage unrelated to either gamete formation or fertilization. Sporogenesis (that includes meiosis) occurs producing spores that germinate into sporophytes.
7. Leptotene and zygotene are the stages that occur during _____________ of meiosis.
b) prophase II
c) metaphase II
Explanation: Leptotene and zygotene are the stages that occur during prophase II in the meiosis. During the leptotene, the chromosomes become microscopically visible and during zygotene visible association of homologues can be seen.
8. Chiasmata are ____ shaped structures.
Explanation: Chiasmata (singular chiasma) are X-shaped structures located at the sites on chromosomes where crossing over between two DNA molecules of the two chromosomes has occurred in the past.
9. Aneuploidy is the condition associated with ______________
a) transcription inefficiency
b) fragile chromosomes
c) abnormal chromosome umber
d) inability to perform meiosis
Explanation: An erroneous meiotic division can lead to the formation of a gamete that contains abnormal number of chromosomes. When such gametes fuse with a normal gamete, the resulting zygote contains an abnormal chromosome number, this condition is termed aneuploidy.
10. A fetus with which of the following abnormalities might not succumb soon after birth?
b) trisomy 13
c) trisomy 18
d) trisomy 21
Explanation: Although both types of aneuploidy – monosomy (absence of a chromosome) and trisomy (presence of an extra chromosome) are lethal. But fetus with trisomy 21 can survive beyond first few weeks to months after birth.
11. __________ in males occurs with a much lower level of chromosomal abnormalities than in females.
Explanation: It is estimated that about 20 to 25 percent of human oocytes are aneuploid, which is much higher than the human spermatozoa. It is hence believed that meiosis in males occurs with a much lower frequency of chromosomal abnormalities than in females.
12. Presence of an extra copy of which chromosome leads to the Doen syndrome?
a) chromosome 9
b) chromosome 11
c) chromosome 17
d) chromosome 21
Explanation: Chromosome 21, consisting of fewer than 400 genes is the smallest human chromosome, the presence of an extra copy of this gene (trisomy 21) leads to the Down syndrome characterized by various mental impairments.
13. The absence of second X chromosome in a female leads to _______________________
a) Down syndrome
b) Turner syndrome
c) Alzheimer’s disease
Explanation: The absence of a second sex chromosome (denoted XO) develops into a female with Turner Syndrome. The Turner syndrome is characterized by genital impairment and abnormal body structure.
14. Klinefelter syndrome is associated with ________________
a) human males
b) human females
Explanation: Klinefelter syndrome is associated with human males who have one extra copy of the female sex chromosome (XXY), characterized by mental retardation, underdevelopment of genitalia and development of female characteristics.
15. The likelihood of having a child with Down syndrome increases with _________________
a) age of father
b) age of mother
c) birth of siblings
d) fertilization rate
Explanation: It is believed that the likelihood of having a child with Down syndrome increases with the age of mother – from 0.05% for mothers 19 years of age to greater than 3% for mothers of age 45.
Sanfoundry Global Education & Learning Series – Cell Biology.
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