BIMM 110 Lecture Notes - Lecture 11: Housekeeping Gene, Post-Translational Modification, Glycosylation

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magentawoodchuck427

25 Feb 2017

School

UCSD

Department

Biology/Molec Biol, Microbiol

Course

BIMM 110

Professor

Ella Tour

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Document Summary

Lecture 3: cystic fibrosis, mutations + their effect (pt2) In the lungs of patients with cystic fibrosis: epithelial cells do not secrete enough mucus, not enough na+ and cl- ions are secreted into the mucus. Cftr is needed for the maintenance of enough sodium in the mucus. Cl- is secreted and na+ follows through a different channel. Without cftr, not enough na+ and cl- are secreted. This is in the sweat glands: cftr is not secreted into the mucus, pathogens are not absorbed from the mucus. Cftr is a transporter that uses atp hydrolysis to transport cl-ions against their concentration gradient: true, false. Cl- ions are pumped down their concentration gradient. Direction of flow depends on where less cl- ions are. In the mucus, there are less cl- than in the lung cells when cftr opens, cl- flows out into the mucus.

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Part A

The ultimate problem with cholera that can lead to death is __________.

only water loss

fluid loss with electrolyte concentrations remaining normal

severe dehydration and electrolyte imbalance

only electrolyte loss

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Part B

The loss of chloride ions is occurring as a result of an continuously open __________, found in certain intestinal epithelial cells.

chloride channel protein

sodium pump

ATP dependent sodium/potassium pump

potassium pump

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Part C

The main purpose of the chloride channel proteins on the apical surface of the intestinal epithelial cells is to create an osmotic gradient that ultimately causes __________ to move through the intestinal epithelium and into the intestinal lumen to assist in the formation of mucus. These are the same chloride channel proteins, adversely affected in cystic fibrosis.

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Part D

The main physiologic mechanism used to control the opening of the chloride channel protein is through the use of __________.

G proteinâlinked receptors

potassium pump

enzyme-linked receptors

sodium pump

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Part E

The main factor that causes cholera is the overstimulation of __________ by the __________.

guanylate cyclase; the bacterium Vibrio cholerae

adenylate cyclase; the bacterium Vibrio cholerae

guanylate cyclase; cholera toxin

adenylate cyclase; cholera toxin

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Part F

The normal physiologic mechanism used by G proteinâlinked receptors is for a ligand to bind to the G proteinâlinked receptor; this in turn activates __________ located in the intracellular side of the plasma membrane, which eventually leads to the physiologic effector action.

diacylglycerol

inositol triphosphate

G protein

cyclic AMP

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Part G

Cholera toxin bypasses the normal sequential cascade of events involving G protein activation. The __________subunit of cholera toxin enters into the cell and directly activates __________. This leads to a non-physiologic (non-homeostatic) action of inappropriately maintaining the chloride channel proteins open. This causes excessive __________, sodium, and water to leave the intestinal epithelial cells.

A; G protein; chloride

B; G protein; chloride

B; inositol triphosphate; calcium

A; diacylglycerol; chloride

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Part H

A defect in the chloride channel protein, causing it to not open, will _________ the chloride, sodium, and water loss in cholera. However, it will also cause the individual to have __________ mucus.

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Part I

A drug that prevents the cholera toxin from attaching to the __________ in the intestinal epithelial cell could be a useful treatment.

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Part J

The best method to reduce the spread of cholera is to __________.

never travel to underdeveloped countries

provide properly treated water supplies

give everyone antibiotics

give everyone antacids

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?

1-mucus in the mucus membrane is an example of the ?

a- first

b-second

c-third line of defense

2-which of the following is not a first line of defense?

a- skin

b- tears

c- saliva or fever

3-what type of cell leaves the bloodstream and matures into amacrophage?

a- monocyte

b- lymphocyte

c-eosinophil

4- which blood cells scan for _____ on the surface of pathogenicmicrobes?

1- PRRs

2- PAMPs

3- PMNs

5-fixed macrophages that are found in the lung are called?

a-alveolar

b- lymphocyte

c-osinophil

6-during ingestion pesudopods of a phagocyte fuse surronding themicroorganism in a (n)?

a-phagosome

b- granule

c- inclusion bod

d- histiocyte

7-interferons are produced by certain animal cells are afterbeing infected by?

a-protozoa

b- bacteria

c- virses

8-when macrophages ingest microorganism they fuse with thisorganelle to destory the infectious agent?

a- chloroplast

b- lysosome o

c-endoplasmic reticlum

9-chemicals realsed by defensive cells that regulate intensityand duration of immune response are called ?

a-antibodies

b- cytokines

c-peroxides

10-which is not a benefit of fever?

a-reduce iron availability to pathogens

b- ill temp sensetive infectious agent

c- tachyecadia

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BIMM 110 Lecture Notes - Lecture 11: Housekeeping Gene, Post-Translational Modification, Glycosylation

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