Question

cystic fibrosis: an overview of geneticscystic fibrosis (cf) is a genetic disorder that primarily affects the respiratory, digestive, and reproductive systems. it is caused by mutations in the cftr (cystic fibrosis transmembrane conductance regulator) gene located on chromosome 7.the cftr protein is essential for regulating the movement of chloride ions across cell membranes, which helps maintain the balance of salt and water in various tissues. mutations in the cftr gene disrupt this process, leading to the production of thick, sticky mucus that clogs airways and ducts in the body.mucus blocks airwaysmucus blocks pancreatic and bile ductsthe location of the cftr gene on chromosome 7(cftr = cystic fibrosis transmembrane conductance regulator)symptomsthe symptoms of cystic fibrosis can vary but often include:- chronic respiratory infections; persistent coughing.- difficulty breathing due to mucus in the lungs.- digestive problems and difficulty absorbing nutrients.geneticscystic fibrosis is caused by recessive mutations in the cftr gene. over 2,000 different mutations in the cftr gene have been identified, with the most common being δf508, a deletion of three dna bases that results in a defective protein.individuals with cystic fibrosis inherit two defective copies of the cftr gene, one from each parent. cystic fibrosis follows an autosomal recessive inheritance pattern:- carriers: a person with one normal cftr allele and one mutated allele is a carrier. carriers typically do not exhibit symptoms of the disease.- affected individuals: a person with two mutated cftr alleles develops cystic fibrosis1. create a punnett square that shows the inheritance pattern of cf when both parents are carriers.| | a | a ||---|---|---|| a | aa | aa || a | aa | aa |% normal $\boldsymbol{25%}$ %carrier $\boldsymbol{50%}$ % cf $\boldsymbol{25%}$2. if one parent has cf and the other is a carrier.| | a | a ||---|---|---|| a | aa | aa || a | aa | aa |% normal __ %carrier $\boldsymbol{50%}$ % cf $\boldsymbol{50%}$3. if one parent has cf and the other does not carry the cf gene. you will need to fill in parent genes.% normal %carrier % cf __4. suggest a reason why a carrier of cf does not have symptoms of the disorder.5. what is the relationship between genes and chromosomes?6. where is the cftr gene located?

Explanation:

Step1: Correct Q1 percentages

CF is autosomal recessive: $AA$ = normal, $Aa$ = carrier, $aa$ = CF.
From Punnett square:

• % Normal: $\frac{1}{4} \times 100 = 25\%$
• % Carrier: $\frac{2}{4} \times 100 = 50\%$
• % CF: $\frac{1}{4} \times 100 = 25\%$

Step2: Correct Q2 parent genotypes & percentages

CF parent = $aa$, carrier = $Aa$. Punnett square:

	$A$	$a$
$a$	$Aa$	$aa$

• % Normal: $\frac{0}{4} \times 100 = 0\%$
• % Carrier: $\frac{2}{4} \times 100 = 50\%$
• % CF: $\frac{2}{4} \times 100 = 50\%$

Step3: Fill Q3 Punnett square & percentages

CF parent = $aa$, non-carrier = $AA$. Punnett square:

	$A$	$A$
$a$	$Aa$	$Aa$

• % Normal: $\frac{0}{4} \times 100 = 0\%$
• % Carrier: $\frac{4}{4} \times 100 = 100\%$
• % CF: $\frac{0}{4} \times 100 = 0\%$

Step4: Answer Q4 (no calculation)

Carriers have one normal $CFTR$ allele that produces functional CFTR protein, which is enough to maintain normal chloride ion regulation and prevent mucus buildup.

Step5: Answer Q5 (no calculation)

Genes are segments of DNA that code for traits; chromosomes are structures made of DNA and proteins that carry multiple genes (genes are located on chromosomes).

Step6: Answer Q6 (no calculation)

The CFTR gene is located on chromosome 7.

Answer:

1. % Normal: 25%, % Carrier: 50%, % CF: 25%
2. % Normal: 0%, % Carrier: 50%, % CF: 50%
3. Punnett square (parent genes: CF parent = $aa$, non-carrier = $AA$):

	$A$	$A$
$a$	$Aa$	$Aa$

% Normal: 0%, % Carrier: 100%, % CF: 0%

1. Carriers have one normal $CFTR$ allele that produces enough functional CFTR protein to maintain normal bodily function, so they do not develop symptoms.
2. Genes are specific DNA segments that encode genetic information, and chromosomes are larger structures composed of DNA and proteins that contain many genes (genes are physically located on chromosomes).
3. The CFTR gene is located on chromosome 7.