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Adenosine deaminase (ADA) deficiency is an autosomal recessive disorder that affects the immune system - Scottish Highers Human Biology - Question 8 - 2019
Question 8
Adenosine deaminase (ADA) deficiency is an autosomal recessive disorder that affects the immune system. It is caused by a mutation in the gene that codes for this en... show full transcript
Worked Solution & Example Answer:Adenosine deaminase (ADA) deficiency is an autosomal recessive disorder that affects the immune system - Scottish Highers Human Biology - Question 8 - 2019
Step 1
Describe the difference between an autosomal disorder and a sex-linked disorder.
Answer
An autosomal disorder is one where the gene mutation is located on one of the 22 pairs of autosomes, while a sex-linked disorder is caused by mutations located on the X or Y chromosomes. This means that autosomal disorders can affect individuals regardless of their sex, whereas sex-linked disorders predominantly affect one sex more than the other due to their location on the sex chromosomes.
Step 2
Step 3
Individuals Q and R plan to have a child together. Use information from the chart to explain why it is difficult to predict the chances of their child having the disorder.
Answer
It is difficult to predict the chances of Q and R's child having the disorder because both Q and R could potentially carry the recessive allele for ADA deficiency, but their exact genotypes are unknown. They may be homozygous dominant (AA), heterozygous (Aa), or one could be affected (aa), and the combinations affect the probability of the child inheriting the disorder.
Step 4
Suggest how this treatment can help to restore a functional immune system.
Answer
A bone marrow transplant can help restore a functional immune system by introducing healthy stem cells that can produce the necessary lymphocytes, thus compensating for the severely reduced numbers in individuals with ADA deficiency.
Step 5
Describe an advantage and a disadvantage of using amniocentesis rather than chorionic villus sampling (CVS).
Answer
Advantage: Amniocentesis provides a lower risk of miscarriage compared to CVS.
Disadvantage: Amniocentesis requires a longer time to obtain results because it is performed later in the pregnancy.