Genetics Quiz on Heterozygotes

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Questions and Answers

What is indicated by urine that smells like maple syrup in infants?

Excessive hydration

Normal metabolic function

A rare inherited disorder (correct)

Common digestive problems

What role does leucine play in the context of the described disorder?

Increases the availability of all amino acids

Decreases the availability of other amino acids (correct)

Enhances neurotransmitter synthesis

Stimulates cell growth

Which of the following is a symptom of the disorder characterized by sweet-smelling urine?

Increased appetite

Lethargy (correct)

Hypoglycemia

Rapid weight gain

Why is the accumulation of certain substances in the brain considered neurotoxic?

It disrupts neurotransmitter synthesis Signup and view all the answers

What are the potential consequences if the described disorder is not identified or treated?

Progressive and worsening symptoms Signup and view all the answers

What is the primary effect of increased levels of leucine in patients with MSUD?

Interference with the transport of large neutral amino acids Signup and view all the answers

Which age range typically shows symptoms of MSUD?

Between 5 months and 7 years Signup and view all the answers

In which situation do patients with intermittent MSUD most likely exhibit symptoms?

Only during physiologic stress Signup and view all the answers

What percentage of enzyme deficiency is associated with intermediate MSUD?

3%-30% Signup and view all the answers

How does the accumulation of leucine affect brain function?

It reduces the availability of necessary amino acids for neurotransmitter synthesis Signup and view all the answers

When are the symptoms of MSUD typically normal in patients?

In the neonatal period only Signup and view all the answers

What is the role of BCKD in the context of branched-chain amino acids?

It contributes to the metabolism of branched-chain amino acids Signup and view all the answers

What neurotransmitters may be affected by the reduced availability of large neutral amino acids due to leucine accumulation?

Dopamine, norepinephrine, and histamine Signup and view all the answers

What is the probability of children presenting with the disease if one partner is a heterozygote and the other carries a dominant gene?

0% Signup and view all the answers

What is the primary purpose of the Guthrie test?

To screen for Phenylketonuria shortly after birth Signup and view all the answers

What is the common incidence rate of Phenylketonuria in live births?

1 in 13,500-19,000 Signup and view all the answers

At what age do symptoms of Phenylketonuria typically begin to appear?

At 1 year of age Signup and view all the answers

Which of the following symptoms is associated with untreated Phenylketonuria?

Depressed IQ Signup and view all the answers

Why won’t a recessive gene associated with the dominant gene be expressed?

It is masked by the dominant gene Signup and view all the answers

What distinctive odor is associated with urine in Phenylketonuria?

Musty odor Signup and view all the answers

What type of genetic disorder is Phenylketonuria classified as?

Autosomal recessive disorder Signup and view all the answers

What is the primary consequence of phenylalanine accumulation in untreated Phenylketonuria (PKU)?

Development of mousy odor in urine Signup and view all the answers

In patients with PKU, why does tyrosine become an essential amino acid?

The body cannot convert phenylalanine to tyrosine due to enzyme deficiency Signup and view all the answers

What is the range of normal phenylalanine levels in newborns?

0.5mg to 1mg per dL Signup and view all the answers

Which treatment can effectively prevent mental retardation in PKU patients?

Diet low in phenylalanine Signup and view all the answers

Which enzyme is directly responsible for converting phenylalanine to tyrosine?

Phenylalanine hydrolase Signup and view all the answers

What symptoms might a physician expect to see in a 4-day-old infant with potential PKU?

Lethargy, vomiting, and poor feeding Signup and view all the answers

What are the excreted compounds in urine that relate to Phenylketonuria?

Phenyl ketones Signup and view all the answers

How do cofactors relate to phenylalanine metabolism?

They help decrease the energy of the reaction Signup and view all the answers

What is the significance of diagnosing PKU early in childhood?

It allows for dietary management to enable normal development. Signup and view all the answers

Which statement about Tetanus and its symptoms is accurate?

Tetanus can cause alternating periods of hypotonia and hypertonia. Signup and view all the answers

What condition is characterized by a significant posture called Opisthotonus?

Hypertonic state Signup and view all the answers

Which enzymatic function is associated with BCKD in amino acid metabolism?

Inactivates through phosphorylation. Signup and view all the answers

What does a normal CSF fluid appear to be in a lumbar puncture?

Clear and colorless Signup and view all the answers

In the context of CSF analysis, what do high levels of RBC indicate?

Potential bleeding or injury Signup and view all the answers

What implication does alternating hypotonia and hypertonia have for diagnosis?

It complicates the understanding of underlying conditions. Signup and view all the answers

Which of the following components is NOT part of the BCKD multienzyme complex?

Cyclin D Signup and view all the answers

Study Notes

Genetics and Inheritance of Disease

Heterozygote partner's offspring have a zero chance of recessive disease if paired with a dominant gene carrier or non-carrier.
Presence of a dominant gene masks expression of recessive gene.

Phenylketonuria (PKU)

Diagnostic test for PKU, known as the Guthrie test, is performed on infants shortly after birth.
Incidence of PKU ranges from 1 in 13,500 to 1 in 19,000 live births.
Symptoms typically manifest around 1 year of age and can lead to depressed IQ if untreated.
Key symptoms include musty odor in urine and hypopigmentation.

Pathophysiology of PKU

In patients, phenylalanine accumulates due to lack of enzyme converting it to tyrosine.
Elevated phenylalanine levels: normal newborns have levels of 0.5 - 1 mg/dL; affected individuals have significantly higher levels.
Phenyl ketones in urine lead to the name "Phenylketonuria."

Treatment of PKU

A lifelong diet low in phenylalanine can prevent mental retardation associated with PKU.
Tyrosine becomes an essential amino acid for those incapable of metabolizing phenylalanine.

Case Study: Newborn Presentation

4-day-old infant exhibits lethargy, vomiting, and poor feeding.
No complications noticed at delivery, awaiting newborn screening results for PKU.

Neurological Manifestation (Tetanus)

Older individuals may experience periods of hypotonia and hypertonia due to tetanus, with Opisthotonus posture noted in severe cases.

Maple Syrup Urine Disease (MSUD)

BCKD deficiency affects metabolism of branched-chain amino acids and can present in varying severity.
Symptoms can occur in infancy or later, typically between 5 months to 7 years of age.
Two types of MSUD manifestations:
- Intermittent: Symptoms during stress (illness, fever).
- Severe: Symptoms present early in life.

Clinical Manifestations of MSUD

Toxicity of accumulated leucine disrupts transport of large neutral amino acids across the blood-brain barrier.
Results in reduced availability of amino acids needed for brain growth, neurotransmitter synthesis (dopamine, serotonin).
Symptoms include weight loss, lethargy, and alternating hypotonia and hypertonia.
Sweet-smelling urine indicates ketone buildup.

Hormonal and Neurotoxic Effects of Leucine

High leucine levels disrupt neurotoxic processes, affecting neurotransmitter synthesis and neuron growth.
Interferes with myelin synthesis and cellular volume regulation.

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Description

Test your knowledge on heterozygotes and genetic predispositions with this quiz. Explore how dominant and recessive genes interact, including the implications for genetic inheritance. Ideal for students studying genetics or related fields.