Download Practice - Long Free Response Question Honors Biology Cystic

Practice - Long Free Response Question Honors Biology
Cystic fibrosis (CF) is an autosomal, recessive trait (f). In people with CF, a defective gene causes a thick,
buildup of mucus in the lungs, pancreas and other organs. In the lungs, the mucus clogs the airways and
traps bacteria leading to infections, extensive lung damage and eventually, respiratory failure. In the
pancreas, the mucus prevents the release of digestive enzymes that allow the body to break down food and
absorb vital nutrients.
Allison has a family history of Cystic Fibrosis, however she does not have the disease. Andrew and Allison
have had a family of several children, some children have CF.
Cystic Fibrosis Pedigree
1) Explain based on genotypes/phenotypes what is the chance for them of having another child with CF
(punnett square)?
2) Compare the probability of their offspring to the actual offspring they have. Be sure to address all
possible genotypes/phenotypes in your comparison.
3) Does the sex of the child affect the probability of getting CF – explain based on your knowledge of
genes and chromosomes.
Located on human chromosome 7, the CFTR gene is made up of 250,000 DNA nucleotides. CFTR stands
for Cystic Fibrosis Transmembrane Conductance Regulator. The CFTR protein functions as a channel for
the movement of chloride ions in and out of cells, which is important for the salt and water balance on
epithelial surfaces, such as in the lungs or pancreas. Changes in the CFTR gene can affect the structure of
the CFTR protein.
Andrew and Allison each have the CFTR genes sequenced. Allison has the following DNA sequence for
CFTR.
3’ – CTG TGT TCT GTA AAC ATA TGG CTA ATT – 5’
4) What is the amino acid sequence for the DNA strand (show your work for both transcription and
translation)? [Table of codons is on the next page]
One of Andrew’s genes that were sequenced resulted in the following amino acid sequence
ASP-THR-ARG-HIS-LEU
5) What type of mutation is present in Andrew’s CFTR gene? Explain.
Andrew’s family is from Brazil. In the isolated village of the Amazon River Valley where Andrew’s
parents are from – the incidence of cystic fibrosis (ff) among the villagers is 0.5%. Assume that the
population is in Hardy-Weinburg Equilibrium.
p² + 2pq + q² = 1 for genotype frequency
p + q = 1 for allele frequency
6) What is the frequency of completely normal individuals in the Amazon River Valley village population?
7) What is the frequency of the cystic fibrosis allele in the population?
Dr. Atalu, a paleontologist from Univerisy of Recife, has been researching the evolution of the
CFTR gene in villagers in the Amazon rain forest. While on one of his recent archaeological digs he found
a fossilized human skeleton with evidence of Cystic Fibrosis. The fossilized skeleton was sent back to the
University of Recife for radiometric carbon dating.(Half-life of C-14 is 5,730 years. N-14 is the daughter
isotope).
Fraction of original material where
y= the fraction of the original material
t=the # of half-lives
8) If the skeleteon has undergone 3 half-lives – what percent of the N-14 remains?
9) After 3 half-lives, how old is the fossilized skeleton?
Questions
1) Explain based on genotypes/phenotypes what is the chances for them of having another child with CF?
2) Compare the probability of their offspring to the actual offspring they have. Be sure to address all
possible genotypes/phenotypes in your comparison.
3) Does the sex of the child affect the probability of getting CF – explain based on your knowledge of
genes and chromosomes.
4) What is the amino acid sequence for the DNA strand (show your work for both transcription and
translation)? [Table of codons is on the next page]
5) What type of mutation is present in Andrew’s CFTR gene? Explain.
6) What is the frequency of completely normal individuals in the Amazon River Valley village population?
7) What is the frequency of the cystic fibrosis allele in the population?
8) If the skeleteon has undergone 3 half-lives – what percent of the N-14 remains?
9) After 3 half-lives, how old is the fossilized skeleton?