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Q44 — TLR7/8 Activation in Sperm Sex Sorting

Theoretical A Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Reproductive Physiology

Approximately 50% of epididymal sperm express Toll-like receptors 7/8 (TLR7/8), which are encoded on the X chromosome. The researchers investigated the effects of their activation in mice sperm cells by a specific ligand — R848. To do that they performed several experiments consisting of a swim-up method and in vitro fertilization (IVF). The obtained data is presented below.

Diagram of the swim-up method used to sort sperm by motility, separating an upper layer (U) of highly motile sperm from a lower layer (L) that remains in the seminal plasma. Figure 1. Swim-up method - technique designed to sort spermatozoa by motility and the capability to swim upwards in the tube out of the seminal plasma; U - upper layer, L - lower layer.

Bar charts comparing sperm straight-line velocity with and without R848 across glucose concentrations, the distribution of X- and Y-bearing sperm in the upper layer after R848 treatment, and the sex ratio of embryos from IVF using untreated versus upper- and lower-layer sperm. Figure 2. A Comparison of straight-line velocity (VSL) of spermatozoa in different glucose concentrations (mM) without (C) and with (R) R848. ‘’ - significant difference between C and R. B Distribution of X chromosome- and Y chromosome-bearing spermatozoa in the upper layer without (Ct.) and with R848. C Comparison of sex of the embryos obtained from IVF with untreated sperm cells (Ct.) in contrast to sperm cells from the upper (U) and lower (L) layers of the swim-up test tube separated after treatment with R848.*

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. Activation of TLR7/8 on sperm cells increases their motility.
B. Following IVF using the high-mobility sperm, more than 80% of the embryos were XY.
C. Ligand activation of TLR7/8 together with the swim-up method could be used to sort X chromosome- and Y chromosome-bearing sperm cells.
D. The significant effect of the TLR7/8 activation on sperm motility is observed only in the presence of glucose.
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Question reproduced from IBO 2024, Theoretical Exam Part A, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)