Summary
Sex chromosome aneuploidies: Turner is XO and Klinefelter is XXY.
In depth
Turner syndrome (45,X) gives females with short stature, infertility and often heart defects, but normal intelligence. Klinefelter (47,XXY) males are tall, have reduced testosterone and often infertility. Sex chromosome aneuploidies are less severe than autosomal ones because extra X chromosomes are inactivated.
Hormone therapy helps.
Turner syndrome occurs in about 1 in 2000 female births, but most 45,X conceptions end in miscarriage; features include webbed neck, short stature, absent puberty and kidney or heart problems, treated with growth hormone and oestrogen. Klinefelter syndrome occurs in about 1 in 600 males and is often found only in adulthood through infertility; testosterone therapy helps.
Other sex chromosome aneuploidies are XXX (triple X), and XYY, both often mild. Individuals with extra X chromosomes show a Barr body for each extra X, because of inactivation.
Key idea: the Y chromosome, through SRY, determines male development whatever the number of X chromosomes.
Frequently asked questions
What is Turner and Klinefelter Syndromes?
Sex chromosome aneuploidies: Turner is XO and Klinefelter is XXY.
Which area of biology covers Turner and Klinefelter Syndromes, and how advanced is it?
Turner and Klinefelter Syndromes is one of the 54 topics in Genetics. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include X-Chromosome Inactivation, Sex Chromosomes, Down Syndrome.
Can you give an example of Turner and Klinefelter Syndromes?
XYY males are typically tall and often undiagnosed.
What should I learn before Turner and Klinefelter Syndromes?
Work through the Beginner topics in Genetics first, such as Heredity, Gene, Allele, then return to Turner and Klinefelter Syndromes. Intermediate topics assume the Beginner vocabulary.
What topics are related to Turner and Klinefelter Syndromes?
The closest topics to Turner and Klinefelter Syndromes are X-Chromosome Inactivation, Sex Chromosomes, Down Syndrome, Nondisjunction. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Turner and Klinefelter Syndromes?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Turner and Klinefelter Syndromes. To practise the whole of Genetics, use the Genetics quiz.
How is Turner and Klinefelter Syndromes different from X-Chromosome Inactivation?
Turner and Klinefelter Syndromes: Sex chromosome aneuploidies: Turner is XO and Klinefelter is XXY. X-Chromosome Inactivation: One X chromosome in each female cell is silenced as a Barr body to equalise gene dosage. Read both side by side and note what each one explains.
How should I study Turner and Klinefelter Syndromes step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with X-Chromosome Inactivation and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.