MODULE 14                                                                            Sex Determination

How is Sex Determined?

Your Mission:

 A question on many student’s minds is how is sex determined?  Why am I a boy or a girl?  To examine this further go to the National Center for Biotechnology Information (NCBI), http://www.ncbi.nlm.nih.gov/.  You have just entered the NCBI website.  “Established in 1988 as a national resource for molecular biology information, NCBI creates public databases, conducts research in computational biology, develops software tools for analyzing genome data, and disseminates biomedical information - all for the better understanding of molecular processes affecting human health and disease.”  On the right hand side of the page find Hot Spots.  Scroll down and click on Genes & Disease.  You just entered the part of the site that deals with the relationships between chromosomes.  Select the preface link at the top of the page.

              1.  How many chromosomes do humans have?

              2. How many pairs of chromosomes do humans have?

              3. What are the two types of chromosomes?

Now click on Full Content to return to the Genes and Disease page.  Scroll down and click on Male-Specific Diseases.

• List four male specific diseases.

Click the back arrow and return to the full content page.  Now find SRY: Sex determination and click on the link.

• What is the male genotype? Female genotype?
• Explain how there can be XY females or XX males.

Click on the Y chromosome at the top of the page.

• How many genes are located on the Y chromosome?
• Is the Y chromosome large or small compared to other chromosomes?

Click on MapViewer.

• What other diseases are found on the Y chromosome?

Summary:  Write a brief summary of what you learned in this assignment.  Explain how a scientist may use the tools and resources that you just used to make scientific breakthroughs.  Why is it important in the 21st century to be aware of advances in molecular biology and the human genome?

ANSWER KEY       MODULE 14              How is Sex Determined?

Your Mission:

 A question on many student’s minds is how is sex determined?  Why am I a boy or a girl?  To examine this further go to the National Center for Biotechnology Information (NCBI), http://www.ncbi.nlm.nih.gov/.  You have just entered the NCBI website.  “Established in 1988 as a national resource for molecular biology information, NCBI creates public databases, conducts research in computational biology, develops software tools for analyzing genome data, and disseminates biomedical information - all for the better understanding of molecular processes affecting human health and disease.”  On the right hand side of the page find Hot Spots.  Scroll down and click on Genes & Disease.  You just entered the part of the site that deals with the relationships between chromosomes.  Select the preface link at the top of the page.

                  1.  How many chromosomes do humans have? 46

                  2. How many pairs of chromosomes do humans have? 23

                  3. What are the two types of chromosomes? Autosomal and Sex

Now click on Full Content to return to the Genes and Disease page.  Scroll down and click on Male-Specific Diseases.

• List four male specific diseases. Alport Syndrome, Male Pattern Baldness, Prostate Cancer, SRY Sex Determination

Click the back arrow and return to the full content page.  Now find SRY: Sex determination and click on the link.

• What is the male genotype? Female genotype? Male – XX, female - XY
• Explain how there can be XY females or XX males. XY females have had the expression of SRY disputed or blocked. XX males have a small portion of the SRY gene, that probably got onto the X chromosome through crossing over.

Click on the Y chromosome at the top of the page.

• How many genes are located on the Y chromosome? Over 200
• Is the Y chromosome large or small compared to other chromosomes? Much smaller

Click on MapViewer.

• What other diseases are found on the Y chromosome? Short stature, idiopathic familial, Leri-Weill dyschondrosteosis, Gonadal dysgenesis,  Leukemia, Azoospermia, Retinitis pigmentosa