7Cystic fibrosis (recessive) Primarily whites of European descentstrikes 1 in 2500 births1 in 25 whites is a carrier (Aa)normal allele codes for a membrane protein that transports Cl- across cell membranedefective or absent channels limit transport of Cl- & H2O across cell membraneThick, sticky, mucus coats around cellsmucus build-up in the pancreas, lungs, digestive tract & causes bacterial infectionswithout treatment children die before 5; with treatment can live past their late 20snormal lung tissueCystic fibrosis is an inherited disease that is relatively common in the U.S. Cystic fibrosis affects multiple parts of the body including the pancreas, the sweat glands, and the lungs. When someone has cystic fibrosis, they often have lots of lung problems. The cause of their lung problems is directly related to basic problems with diffusion and osmosis in the large airways of the lungs.People without cystic fibrosis have a small layer of salt water in the large airways of their lungs. This layer of salt water is under the mucus layer which lines the airways. The mucus layer in the airways helps to clear dust and other inhaled particles from the lungs.
8bacteria & mucus build up mucus secreting glands Effect on LungsChloride channeltransports salt through protein channel out of cellOsmosis: H2O follows Cl–normal lungsairwayCl–Cl– channelH2Ocells lining lungscystic fibrosisCl–In people without cystic fibrosis, working cystic fibrosis proteins allow salt (chloride) to enter the air space and water follows by osmosis. The mucus layer is dilute and not very sticky.In people with cystic fibrosis, non-working cystic fibrosis proteins mean no salt (chloride) enters the air space and water doesn't either. The mucus layer is concentrated and very sticky.People with cystic fibrosis have lung problems because:Proteins for diffusion of salt into the airways don't work. (less diffusion)Less salt in the airways means less water in the airways. (less osmosis)Less water in the airways means mucus layer is very sticky (viscous).Sticky mucus cannot be easily moved to clear particles from the lungs.Sticky mucus traps bacteria and causes more lung infections.Therefore, because of less diffusion of salt and less osmosis of water, people with cystic fibrosis have too much sticky mucus in the airways of their lungs and get lots of lung infections. Thus, they are sick a lot.H2Obacteria & mucus build upthickened mucus hard to secretemucus secreting glands
10Tay-Sachs (recessive) Primarily Jews of eastern European (Ashkenazi) descent & Cajuns (Louisiana)1 in 3600 birthsnon-functional enzyme fails to breakdown lipids in brain cellsfats collect in cells destroying their functionsymptoms begin few months after birthseizures, blindness, muscular & mental degenerationchild usually dies before 5
11Sickle cell anemia (recessive) Primarily Africans1 out of 400 African Americanscaused by substitution of a single amino acid in hemoglobinwhen oxygen levels are low, sickle-cell hemoglobin crystallizes into long rodsdeforms red blood cells into sickle shapesickling creates pleiotropic effects = cascade of other symptoms
12hydrophilic amino acid hydrophobic amino acid Sickle cell anemiaSubstitution of one amino acid in polypeptide chainhydrophilic amino acidhydrophobic amino acid
13Huntington’s chorea (dominant) Dominant inheritancerepeated mutation on end of chromosome 4mutation = CAG repeatsglutamine amino acid repeats in proteinone of 1st genes to be identifiedbuild up of “huntingtin” protein in brain causing cell deathmemory lossmuscle tremors, jerky movements“chorea”starts at age 30-50early death: years after start1872Testing… Would you want to know?
23Hemophilia is a sex-linked recessive trait defined by the absence of one or more clotting factors. These proteins normally slow and then stop bleeding.Individuals with hemophilia have prolonged bleeding because a firm clot forms slowly.Bleeding in muscles and joints can be painful and lead to serious damage.Individuals can be treated with intravenous injections of the missing protein.
24Genetics & cultureAll cultures have a taboo against incest.laws or cultural taboos forbidding marriages between close relatives are fairly universalFairly unlikely that 2 unrelated carriers of same rare harmful recessive allele will meet & matematings between close relatives increase risk“consanguineous” (same blood) matingsindividuals who share a recent common ancestor are more likely to carry same recessive alleles
25Chromosomal abnormalities Incorrect number of chromosomesnondisjunctionchromosomes don’t separate properly during meiosisbreakage of chromosomesdeletionduplicationinversiontranslocation
26NondisjunctionProblems with meiotic spindle cause errors in daughter cellshomologous chromosomes do not separate properly during Meiosis 1sister chromatids fail to separate during Meiosis 2too many or too few chromosomes2nn-1nn+1
27Alteration of chromosome number error in Meiosis 1error in Meiosis 2all with incorrect number1/2 with incorrect number
28Nondisjunction Offspring has wrong chromosome number trisomy monosomy cells have 3 copies of a chromosomemonosomycells have only 1 copy of a chromosomen+1nn-1ntrisomy2n+1monosomy2n-1
29Down syndromeTrisomy 213 copies of chromosome 211 in 700 children born in U.S.Chromosome 21 is the smallest human chromosomebut still severe effectsFrequency of Down syndrome correlates with the age of the mother
31Down syndrome & age of mother Mother’s ageIncidence of Down SyndromeUnder 30<1 in 1000301 in 900351 in 400361 in 300371 in 230381 in 180391 in 135401 in 105421 in 60441 in 35461 in 20481 in 16491 in 12
32Genetic testing Amniocentesis in 2nd trimester Analysis of karyotype sample of embryo cellsstain & photograph chromosomesAnalysis of karyotype
36Klinefelter’s syndrome XXY maleone in every 2000 live birthshave male sex organs, but are sterilefeminine characteristicssome breast developmentlack of facial hairtallnormal intelligence
37Jacob’s syndrome male XYY Males 1 in 1000 live male births extra Y chromosomeslightly taller than averagemore activenormal intelligence, slight learning disabilitiesdelayed emotional maturitynormal sexual development
38Trisomy X XXX 1 in every 2000 live births produces healthy females Why?Barr bodiesall but one X chromosome is inactivatedHow many Barr bodies would you expect?
39Turner syndrome Monosomy X or X0 1 in every 5000 births varied degree of effectswebbed neckshort staturesterileHow many Barr bodies would you expect?
40Changes in chromosome structure deletionloss of a chromosomal segmentduplicationrepeat a segmentinversionreverses a segmenttranslocationmove segment from one chromosome to anothererror of replicationerror of crossing over
41Meanwhile in Plants...Plants are very tolerant of polyploid mutations. Offspring with extra sets of chromosomes experience gigantism. Most crops are polyploid.