BIOL1004 Study Guide - Final Guide: Oligosaccharide, Sickle-Cell Disease, Phosphodiester Bond

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Cystic Fibrosis

• Most common lethal inherited disease of Caucasians, less common in other

ethnicities

• Recessive

• Survival rates are improving

Detection

• Historically detected by high amount of Na+ and Cl- in babies sweat kiss

your baby campaign

• Protein has both hydrophobic and hydrophilic regions → lead to

postulation of integral membrane protein

• It was later discovered the disease was caused by a defective chloride ion

channel

• Protein was named Cystic Fibrosis Transmembrane conductance

regulator

Treatment

• New treatment option: Kalydeco —> families persuade government to put it on the

PBS

• Non chemical treatment option: aerosol delivery treatment of salt water, used

overnight, rehydrates the layer of sticky mucus lining their lungs and

eliminates bacteria containing mucus more easily

Mechanism

• The defective protein chloride ion channel located at the surface of epithelial

cells (in lungs, intestines and pancreas)

• Opening of channel is activated by increased levels of cAMP within cells

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• When the chloride ion moves across the membrane water follows by osmosis

• Sodium ions move through also

Body part

Affect

Why

Lungs

• Bacterial infections

• Difficulty

breathing

Mucus blocks alveoli in

lungs, bronchial

obstruction

Pancreas

• Digestive issues

Mucus blocks pancreatic

ducts

Sugars, amino acids

Small molecules and macromolecules

• Sugars → polysaccharides

• Amino acids → proteins

• Nucleotides → nucleic acids

Fatty acids make up membranes but they are not held together by covalent

bonds and so are not classified as macromolecules

Polymers

• Formed by dehydration reactions

• Broken by hydration reactions

Monosaccharides e.g. glucose join together by glycosidic linkages

(dehydration) to form disaccharides /polysaccharides

POLYSACCHARIDE EXAMPLE:

• Cellulose if formed by linkage of ß glucose molecules by hydrogen bonds

between glucose molecule

o Gives strength to cell walls

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• Starch is formed by linkage of ∂ glucose monomers, O( orientation differs

cellulose

o Branched → cant form wall like structure, energy store

• Glycogen: animal polysaccharide —> also has branching (stored glucose)

DISACCHARIDE EXAMPLE: - sucrose

Ketose sugars: monosaccharide-

containing ketone group e.g. fructose

Aldose sugars: monosaccharide-

containing aldose group e.g. glucose

Structure of amino acid

Amino acids can be neutral non-polar, neutral polar, acidic and basic

Description: Carbon is covalently bonded to four different groups: an amino group, a

carboxyl group, a hydrogen atom, and a variable group symbolised by R.

Main difference: their side chain

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Document Summary

Cystic fibrosis: most common lethal inherited disease of caucasians, less common in other ethnicities, recessive, survival rates are improving. Detection: historically detected by high amount of na+ and cl- in babies sweat (cid:523)(cid:494)kiss your baby(cid:495) campaign(cid:524, protein has both hydrophobic and hydrophilic regions lead to postulation of integral membrane protein. It was later discovered the disease was caused by a defective chloride ion channel: protein was named cystic fibrosis transmembrane conductance regulator. Treatment: new treatment option: kalydeco > families persuade government to put it on the. Pbs: non chemical treatment option: aerosol delivery treatment of salt water, used overnight, rehydrates the layer of sticky mucus lining their lungs and eliminates bacteria containing mucus more easily. Affect: bacterial infections, difficulty breathing, digestive issues. Small molecules and macromolecules: sugars polysaccharides, amino acids proteins, nucleotides nucleic acids. Fatty acids make up membranes but they are not held together by covalent bonds and so are not classified as macromolecules.

Related Questions

Cystic Fibrosis (CF) is an autosomal recessive genetic disease that is characterized by the secretion of thick, abnormal mucous in the lungs. The mutated gene that leads these symptoms is the CF transmembrane conductance regulator (CFTR gene). The encoded protein is a chloride channel that moves chloride ions out of epithelial cells. In a homozygous individual, the lack of this chloride channel function in a mutant slows the flow of water into extracellular spaces. This lack of water export leads to the heavy mucus in the lungs of CF patients. Although children with CF would die in childhood, current treatments provide life expectancies into the 30âs.

CF is the most frequently inherited genetic disorder among American children. It affects 1 of every 2,500 children; 30,000 currently have the disease. Although its frequency is higher in European populations, it affects all human populations. Heterozygous carrier frequencies in the US are estimated to be 1 out of 29 Caucasians, 1 out of 46 Hispanics, 1 out of 61 African Americans and 1 out of 90 Asians. There are genetic screens for carriers of CF but they are not routinely performed despite this high frequency of carriers. At least all states in the US proscribe testing of newborns to identify children with CF early so that treatment can be started. Newborn tests for CF: http://www.cff.org/AboutCF/Testing/NewbornScreening/ScreeningforCF/ . If CF is such a common genetic disease, and such a simple Mendelian trait, why is genetic screening of parents not done more frequently? Is it just economic, a pain to do, or is it more complex such that the results of genetic testing are not just positive or negative?

Answer the following questions:
1. If two parents are heterozygous carriers of CF, show a pedigree with four children showing the incidence of carriers and afflicted children. If each unafflicted child (carrier or not) mates with another person, who has a 1 out of 30 chance of being a carrier of CF, what is the expected incidence CF disease in the third generation (frequency of CF in any one of grandchildren of the original couple)?

2. Pleiotropy of Cystic Fibrosis. Watch the two videos on the left at:

http://www.cftrscience.com/MOD-animation
or, if you can not view these, read the short NIH Genetics Home Reference for Cystic Fibrosis http://ghr.nlm.nih.gov/condition/cystic-fibrosis

Connect the description with one of the following videos, or related ones (there are many) you see:
video (10 minutes) of daily life of a child with Cystic Fibrosis http://www.youtube.com/watch?v=WUsuGKzdDg8
Lauraâs (20 year old) video diary of life with CF http://www.youtube.com/watch?v=Pgrf8qJXhpc&feature=related

In your own words, describe the range of CF phenotypes. List the other organs besides lungs that are affected and how does it affects those organs.

3.The DNA sequence of the CFTR gene is 170,000 base pairs in length and encodes the CFTR protein that is 1480 amino acids long. Open the accompanying text file (in Canvas/Files/Discussion folder) âCFTR gene DNA sequenceâ. You will see an alignment of the NIH human genome sequence of the CFTR gene â called âReferenceâ rather than âwild-typeâ- against a gene sequence containing a common mutation in CFTR. Look at the alignment and determine how the DNA sequence differs between them. What is the position number where they differ? How many and what nucleotides do they differ in? A â-â mark in one sequence in the alignment means that that base sequence is missing the corresponding bases in the other sequence. The sequence is a long one but the differences are in bolded bright red text. Matching sequence is marked with a | linking the two sequences. Look near the sequence AAATATCATC if you use FIND tool in Word.

In another file, you will an alignment of the reference translated into a protein sequence, compared to the mutant allele translated into protein sequence. The differences are again in red whereas the areas where the proteins match are in black. Look at the alignment. How do these two proteins differ? Again, find the position number and describe how they differ at that location. A â-â mark in the alignment means that amino acid is missing when compared to the other sequence.

4. Given that the CFTR gene can be analyzed for a mutation that causes CF, couples interested in being tested as carriers face several choices given the results.
What could be a consequence of a false positive result (couple is identified as carriers but they would not produce any children with symptoms)?

What could be a consequence of a false negative result (a test indicates the couple is not both carriers but they would produce some children with CF)?

5. The sensitivity of the test can vary with ethnic group. The following is a chart from the NCBI Genetic testing site. A sensitivity less than 100% would be likely to produce false negative results from an inability to determine that someone is carrier.

CF Carrier Test Sensitivity by Ethnic Group http://www.ncbi.nlm.nih.gov/projects/GeneTests/static/concepts/primer/ptscarr5.shtml
Ethnic Group ¹	Population Frequency of CF	Sensitivity of Carrier Detection ²
Caucasian	1 in 29	90%
Ashkenazi Jewish	1 in 29	97%
Native American	1 in 32	94%
Latino	1 in 46	57%
African-American	1 in 60	75%
Asian	1 in 90	30%

Why might different ethnic populations differ in the ability of the genetic test to identify carriers of CF?

BIOL1004 Study Guide - Final Guide: Oligosaccharide, Sickle-Cell Disease, Phosphodiester Bond

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