Podcast
Questions and Answers
What is the main consequence of an abnormal gene in relation to phenylketonuria?
What is the main consequence of an abnormal gene in relation to phenylketonuria?
- Decrease in blood phenylalanine levels
- Accumulation of phenylalanine in blood (correct)
- Increase in tyrosine production
- Phenylalanine hydroxylase is produced
Which syndrome is characterized by three copies of chromosome 21?
Which syndrome is characterized by three copies of chromosome 21?
- Turner's syndrome
- Down's syndrome (correct)
- Cri-du-chat syndrome
- Klinefelter's syndrome
What is a common characteristic of Turner’s syndrome?
What is a common characteristic of Turner’s syndrome?
- Mewing cry in affected individuals
- Underdeveloped sexual characteristics (correct)
- Enlarged breasts (gynecomastia)
- Presence of three X chromosomes
What causes Down's syndrome?
What causes Down's syndrome?
In Klinefelter’s syndrome, which chromosomal configuration is present?
In Klinefelter’s syndrome, which chromosomal configuration is present?
Which of the following is associated with Cri-du-chat syndrome?
Which of the following is associated with Cri-du-chat syndrome?
What significant health issue is often seen with Down's syndrome?
What significant health issue is often seen with Down's syndrome?
Which factor is associated with an increased risk of having a child with Down's syndrome?
Which factor is associated with an increased risk of having a child with Down's syndrome?
What are phenylalanine hydroxylase's primary functions?
What are phenylalanine hydroxylase's primary functions?
What is a common trait in children with Klinefelter’s syndrome?
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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