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Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
ISBN: 9781337408332

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BuyFindarrow_forward

Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
ISBN: 9781337408332
Textbook Problem
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Stuck Sperm Cells lining the epididymis secrete a glycoprotein (beta-defensin) that coats sperm and facilitates their passage through cervical mucus. There are two common alleles for human beta-defensin: a wild-type allele (wt) and an allele with a deletion (del). To find out if this genetic variation could affect fertility, Gary Cherr and his colleagues tested the ability of sperm from men with different genotypes to pass through a gel barrier. The barrier was designed to simulate cenrical mucus. The researchers placed sperm on one side of the gel, then used a video camera to record how many passed into the gel over time. FIGURE 41.12 illustrates their results.

Chapter 41, Problem 4DAA, Stuck Sperm Cells lining the epididymis secrete a glycoprotein (beta-defensin) that coats sperm and

FIGURE 41.12 Effect of beta defensin genotype on the ability of sperm to penetrate a gel that simulates cervical mucus. Sperm from 16 men was tested: 4wt/wt, 6wt/del, and 6 del/del.

Fresh sperm were placed on one side of the gel, and a video camera was focused on a region 2.75 mm into the gel. The number of sperm in this region was recorded at one-minute intervals for six minutes. Sperm numbers shown are averages. Bars indicate range.

The beta-defensin gene is an chromosome 20. What percentage of sperm from a heterozygous man would you expect to carry the del allele?

Summary Introduction

To explain: The percentage of sperm from a heterozygous man that would carry the del allele.

Concept introduction: The epididymis is a part of the male reproductive system. Through the epididymis, the sperm travel from the testis to the vas deferens.

Explanation

An experiment was performed by researcher GC and his colleagues about stuck sperms. The cells of the epididymis secrete a beta-defensin protein that aids the sperm to pass through the cervical mucus of the female. The research team conducted the experiment to check if the beta-defensin has any role in fertility. One allele of the gene, coding for the beta-defensin, was wild-type and the other allele was a mutated one. A barrier similar to the cervical mucus was created in the form of a gel...

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