1. What would happen if a child received two different CFTR mutations, one from
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Question
1. What would happen if a child received two different CFTR mutations, one from each parent. Would a child be normal or would the child have CF? What are the variables that you would consider in your answer?
2. What is the principle source of CFTR alleles?
3. Unfortunately, sequencing of Sam’s CFTR gene determines that Sam is also heterozygous for the mutation CTFRW1282X, a mutation that produces a shortened non-functional gene (mutation to a stop codon-Class 1). If Sam and Mariah have a child and that child has with CF, what would the chromosome 7, the CFTF gene enlarged and mutations from Sam and Mariah look like?
4. If Sam and Mariah’s first child had cystic fibrosis, what is the probability that their second child would have cystic fibrosis? Would they be safe? Please justify your answer.
5. What is the probability that if they have three children, two will be normal and one will have cystic fibrosis? Please justify your answer and show your work.
6. Mannose-binding lectin (MBL) binds to the surface of bacterial and fungal cells invading the body to activate a key component of the immune system. One problem that CF patients have is severe and chronic bacterial infections of the lungs, ultimately so damaging the lungs that death occurs. The MBL2 gene is found in a single copy in humans on chromosome 10q11.21-q21. A number of alleles exist in human populations for this gene with differing levels of functional protein. Allele b disrupts protein folding and is a mutation in codon 54 (Gly to Asp) leading to low levels of serum protein. CF patients with low function alleles for MBL have a much poorer prognosis, and often die on the average 8 years earlier than CF patients with normal MBL alleles (allele a). Assume that Sam and Mariah are heterozygous for MBL2 alleles (MBL2a/MBL2b). What proportion of their children would have severe CF disease and a probability of an earlier death? Don’t use a Punnet square and justify your response by showing your work.
Explanation / Answer
1. Cystic fibrosis (CF) is a genetic disorder, which occurs as a result of mutation in CFTR gene. It is a homozygous recessive disorder affects 1 in 2,000 populations in newborns.The gene CFTR encodes for a protein, which moves chloride ions out of epithelial cells, which results in the concomitant efflux of water molecules along with chloride ions by osmosis.
In this case, as the child recieved two copies of mutant allels from their parents, the child will be affected by CF.
2.
he common mutation in CF is a deletion of one codon (three base pairs) of the CFTR protein; this deletion is called “F508.” Because of this mutation, the transport of chloride ions and water molecules across the cell membrane is disrupted. So, the epithelial cells are not kept wet as well as before. As a result, the mucus adheres to the walls of the body tubes instead of its normal slipping over body’s tubes. This result in the clogging of passage ways, so, the CF patients usually suffer from gastrointestinal and respiratory disorders.
Another function of this CFTR protein is it acts as a receptor, which binds the bacteria. This binding is usually followed by the internalization of the bacteria, which is one of the body’s main defence mechanisms against pathogenic bacteria.
The presence of “F508” deletion causes the failure of CFTR protein, and so the bacteria cannot enter the epithelial cells. Among the different strains of salmonella typhi, the entry of 167 strains into the epithelial cells was most inhibited than the other strains.
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