This set of Cytogenetics Multiple Choice Questions & Answers (MCQs) focuses on “Meiosis Prophase 1 : Synaptonemal Complex”.
1. Which of the following doesn’t lead to pairing in meiosis?
a) 0.3% DNA replication that was left after S phase
b) Retardation factor
c) Turbulence factor
d) Precocity factor
Explanation: There is no turbulence factor leading to pairing in prophase, however it is true that the un-replicated DNA helps in pairing. Also precocity theory and retardation theory comes into play.
2. The uncoiling of chromosomal relics leads to pairing.
Explanation: This is stated in the retardation theory that the chromosomal pairing process is quite slow. Then the relics uncoil that leads to proper point to point pairing of each gene.
3. What is the size of each fiber of the synaptonemal complex?
a) 5 nm
b) 10 nm
c) 15 nm
d) 20 nm
Explanation: The 10 nm fibers of synaptonemal complex are responsible for the pairing of homologous chromosomes during meiosis.
4. The synaptonemal complex has ____________ filaments.
Explanation: There are 3 synaptonemal complexes, one central filament and 2 lateral filaments. The LC complex holds the central filament in line with lateral.
5. The fibers of the lateral filament are called____________
c) Synaptic clefts
Explanation: The lateral filament of synaptonemal complex consists of fibers called synaptomere. It is slightly wider than 10 nm.
6. Which of the following is incorrect about lateral filaments?
a) The lateral filaments are composed of chromatids
b) They can be spaced as much as 100-125 nm apart
c) The lateral filaments have DNA elements along with RNA and Proteins
d) The lateral filaments are connected by longitudinal connections
Explanation: The two lateral elements have chromatids, i.e. they have DNA along with RNA and proteins. They are however connected via transverse elements or LC elements making a ladder like an arrangement.
7. During pairing of the chromosomes which of the following is not true?
a) There are 3 lateral filaments A, B, C
b) The A point pairs with adjacent A of other chromatid
c) The B point pairs with adjacent B of other chromatid
d) The C point pairs with C
Explanation: The A point of the synapomere pairs with the A of adjacent synaptomere not chromatid. Only the B is connected to the other chromatid.
8. The zygosome has ________________ head and _________ tail connecting to the opposite zygosome.
a) Straight, straight
b) Folded, folded
c) Folded, straight
d) Straight, folded
Explanation: The head of the zygosome is folded while the tail is straight. The sygosomes from opposite B points interact with each other via this tail portion.
9. The pairing of the chromosome is mediated by _______________ interactions.
Explanation: The tails of two opposite zygosomes are oppositely charged. This brings about pairing by electrostatic interaction.
10. The synaptonemal complex is a portentous complex, which of the protein is not present in it?
a) Rec 11
d) Zip 1
Explanation: Actin is a cytoskeletal element that doesn’t participate in the syanptomenal complex formation. However, the other proteins mentioned and more may be present.
Sanfoundry Global Education & Learning Series – Cytogenetics.
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