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Questions and Answers
What is the main consequence of an abnormal gene in relation to phenylketonuria?
Which syndrome is characterized by three copies of chromosome 21?
What is a common characteristic of Turner’s syndrome?
What causes Down's syndrome?
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In Klinefelter’s syndrome, which chromosomal configuration is present?
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Which of the following is associated with Cri-du-chat syndrome?
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What significant health issue is often seen with Down's syndrome?
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Which factor is associated with an increased risk of having a child with Down's syndrome?
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What are phenylalanine hydroxylase's primary functions?
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What is a common trait in children with Klinefelter’s syndrome?
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Study Notes
Phenylketonuria
- Normal gene produces phenylalanine hydroxylase, which converts phenylalanine to tyrosine.
- Abnormal gene lacks phenylalanine hydroxylase leading to phenylalanine accumulation in the blood, causing phenylketonuria.
Chromosomal Abnormalities
- Faults during meiosis can result in an abnormal number or shape of chromosomes.
- Non-lethal conditions include Down's syndrome and Cri-du-chat syndrome
Down's Syndrome
- Individuals have three copies of chromosome 21 (trisomy 21).
- Caused by a failure to separate during meiosis.
- Characteristics: short stature, pronounced eyelid folds, round face, and protruding tongue.
- Associated with learning disability and shortened life expectancy.
- Increased risk of cardiovascular and respiratory diseases, and early dementia.
- Incidence increases with maternal age, especially over 35 years.
Cri-du-chat Syndrome
- Individuals have a deletion of part of chromosome 5.
- Characterized by a distinctive mewing cry.
- Associated with learning disability.
Abnormalities of the Sex Chromosomes
- Sex chromosomes failing to separate during meiosis can result in an incorrect number of chromosomes.
Turner’s Syndrome
- Individuals have one X chromosome (XO).
- Affected individuals are female with underdeveloped sexual characteristics, and may have coarctation of the aorta (15% of cases).
- Intelligence is usually normal.
Klinefelter’s Syndrome
- Individuals have an XXY chromosome configuration.
- Affected individuals are male, often taller than average, with learning disability.
- Underveloped genitalia and infertility are common.
- Development of feminine characteristics, like enlarged breasts (gynecomastia).
Spot Check
- Oncogene is a gene that can cause uncontrolled cell growth and division, contributing to cancer development.
Review and Revise
- The disorder phenylketonuria is inherited as a recessive disorder and is characterized by a lack of the enzyme phenylalanine hydroxylase.
- This enzyme converts phenylalanine to tyrosine, and in its absence, the former substance accumulates in the blood and is toxic to the nervous system.
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Description
This quiz explores key concepts of genetic disorders, focusing on Phenylketonuria (PKU) and chromosomal abnormalities like Down's syndrome and Cri-du-chat syndrome. Understand the genetic mechanisms, symptoms, and implications of these conditions. Test your knowledge on how genetic factors influence human health.
