Summary Grade 12 Life Sciences - Abnormal Meiosis and Genetic Disorders
9 views 0 purchase
Course
Life Sciences
Institution
12th Grade
This Grade 12 IEB Life Sciences document provides a comprehensive summary of abnormal meiosis and its resulting genetic disorders, including non-disjunction conditions like Down syndrome and Klinefelter's syndrome. With clear explanations of chromosomal mutations and their effects on physical and m...
Abnormal Meiosis
Chromosomal non-disjunction occurs when chromosomes fail to separate correctly during meiosis.
‣ This results in a condition called aneuploidy where zygote has an extra or a missing
chromosome.
‣ A!ected individuals have physical and mental characteristics called syndromes.
Note:
Diagnosis - identifying the nature of an event. (e.g illness)
Prognosis - predicting how the event will develop.
Klinefelters syndrome
‣ occurs in males when a boy is born with an extra copy of the X chromosome (XXY)
‣ This occurs when sex chromosomes in the egg split unevenly
Symptoms:
- Sparse body hair
- Enlarged breasts
- Small testicles and penis
- Not very deep voice
- May interfere with sexual development an fertility
Down syndrome
‣ occurs in children who are born with an extra (third) copy of chromosome number 21 in their cells
this is known as trisomy
How does this come about?
- during oogenesis the two number 21 chromosomes do not separate properly during anaphase
- Result is an egg with two number 21 chromosomes instead of one.
- If egg is fertilised, zygote will have three number 21 chromosomes, and thus each cell has 47
chromosomes instead of 46.
Characteristics:
- varying degrees of mental retardation
- Distinctive "attened facial features and slightly slanted eyes ( due to skin folds at corners of eyes )
- Short stubby #ngers, largish head and ears may develop di!erently
- These can be accompanied by heart defects and other health problems.
- Tend to have a happy and loving nature
- NO CURE!
How common is Down syndrome?
- Relatively common a!ecting 1 in 900 births
- The chances of having a baby with down syndrome increases with the age of the mother - This is
know as the maternal age e!ect, as chromosome have more di$culty separating with age
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller TanyaChigs. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.85. You're not tied to anything after your purchase.
