2 A human diploid cell contains more than 6 billion base pairs of DNA All DNA is packed into 46 chromosomes.
3 Human Genes and Chromosomes Chromosomes 21 and 22 are the smallest human autosomes.
4 Chromosome 21 contains 225 genes Contains associated amyotrophic lateral sclerosis (ALS) Lou Gehrig’s disease.Many regions have no genes at all.Chromosome 22 contains as many as 545 different genesDisorders can cause leukemia and neurofibromatosisLong stretches of repetitive DNA are unstable sites.
5 RememberGenes located close together on the same chromosome are linked, meaning that they tend to be inherited. It is true for many genes but they might be divided by crossing over.
6 Sex- Linked GenesThere is a special patter of inheritance for genes located on the X chromosome or the Y chromosome because they determine the sex. Many sex-linked genes are found on the X- chromosome
7 SEX CHROMOSOMES CAN CARRY OTHER GENES TOO = ___________________ SEX LINKED TRAITSThese traits show up in different_______________ in males and femalesbecause they move with the sex chromosomespercentages
8 ________genes _____ show up _______ Y-LINKED GENES:Genes ______________ chromosomecarried on YEXAMPLE: Hairy pinnaONLYY linkedin males________genes _____ show up _______
9 are carried on the X chromosome X-LINKED____________ GENES:are carried on the X chromosomeX-linked recessive disordersshow up _____________in ______ than femalesbecause males only have______ X chromosome.MORE frequentlyMALESONE
10 Or Males ONLY HAVE ONE X They either have the They are disorder normal DEFECTIVENORMALThey eitherhave thedisorderThey arenormalOr
11 Females have one normal gene that works. FEMALES HAVE TWO X CHROMOSOMESDEFECTIVENORMALDEFECTIVEFemales have one normal gene that works.Females __________ defective recessivealleles to show thedisorderneed 2
12 The X chromosome in males . . . flies WITHOUT a copilot!. . . there’s NO BACK UP X to help them!
13 Examples of ____________________ DISORDERS: ____________________ X-LINKED RECESSIVEExamples of ____________________DISORDERS:____________________HEMOPHILIACOLORBLINDNESSDUCHENNE MUSCULAR DYSTROPHY
14 COLORBLINDNESSCAUSE: Mutation in one of three genes for _______________ carried on X chromosomePersons with this disorder have trouble distinguishing colors._________________colorblindness is most commonSeen in 1 in 10 males1 in 100 femalesColor visionRed-green
16 HEMOPHILIACAUSE: Mutation in genes for __________________ carried ______ chromosomeBlood clotting proteins are missing so person with this disorder can’t stop bleeding when injured; can ________________ from minor cuts or suffer internal bleedingfrom bruises or bumps.Blood clotting proteinson Xbleed to death
17 HEMOPHILIA Treatment: Need ____________ of normal clotting proteins to stop bleeding_____________ in ______ because it isX-linked, but females with ______ recessive hemophilia alleles will also show the trait.1 in 10,000 males has hemophiliainjectionsMore commonmalesTWO
19 Duchenne Muscular Dystrophy CAUSE:deletion in genethat codes for a_______________Results in____________________and loss of ___________________muscle proteinprogressive weakeningskeletal muscle
20 Duchenne Muscular Dystrophy (DMD) SYMPTOMS:1 in 3000 male birthsAppears before age 5Progressive muscle weakeningMost in wheelchair by age 13Eventually lethal
21 ________ traits show up _______ in _______ What’s the pattern:________ traits show up _______ in _________________________ traits:________________________ than females.________________ can be ________._______________________ traits:BOTH ______ & _________ can be ________Y-linked ONLY malesX-linked recessivemore common in malesONLY FEMALES _______ carriersAUTOSOMAL RECESSIVEMALES FEMALES carriers
22 CAT COLOR In cats, a gene that controls the _____________ is carried on the____________________SPOT COLORX chromosomeIn some female cells the X with the allele for orange spotsis switched off and in some cells the X with the allele forblack spots is switched off, so cat has differentcolored spots.See a video
23 CAT COLOR _________ cats have only one X chromosome, so they Male can only have____________ of spots!Maleone colorTHINK ABOUT IT?How many colors of spots could a male cat withKlinefelter syndrome have?
24 ________________ Abnormalities CHROMOSOMAL1 infant in 200 newborns has a chromosomal abnormality28% of first trimester miscarriages have a chromosomal abnormalityAbnormalities in larger chromosomes don’t usually survive
25 ____________________________: Change in the ______________ or CHROMOSOMAL MUTATIONS____________________________:Change in the ______________ or____________ of chromosomesstructurenumber
26 Homologous chromosomes ________________ during MEIOSIS = _________________________One cell gets 2 copies ofthe chromosome theother cell gets none.fail to separateNONDISJUNCTION
29 Nondisjunction Since it happens to a sperm or egg, the new baby can end upwith _____________ of achromosome= __________________ORonly ___________ of a= ___________________3 copiesTRISOMYone copyMONOSOMY
30 Human Abnormalities caused by Non-Disjunction __________________ __________________ __________________Down syndromeKlinefelter syndromeTurner syndrome
34 Down syndrome (Trisomy 21) Most common chromosomal abnormality50% have heart defects that need surgery to repairMild to severe mental retardationIncreases susceptibility to many diseasesRisk of having a child with Down syndrome increases with age of mom
37 Turner syndrome ____ XO 1 in 5000 births Females have only one X chromosome (45,X)Small sizeSlightly decreased intelligence35% have heart abnormalitiesHearing loss commonBroad chestReproductive organs don’t develop at pubertyCan’t have children
39 Klinefelter syndrome 1 in 1000 births Males have extra X chromosomes (Can be XXy, XXXy, or XXXXy) (46,XXY)Average to slight decrease in intelligenceSmall testes/can’t have childrenUsually not discovered until puberty when don’t mature like peers
40 Karyotype (need cells from baby) Can tell __________________ chromosomes__________Some _____________________Can’t see _______________ mutationsMISSING/EXTRAGENDERDELETIONS/INSERTIONSsingle gene
41 If having extra chromosomes causes genetic problems, how come having two X chromosomes in females and one X in males is not a problem?
42 X-chromosome Inactivation In female cells ______ chromosome is randomly ________________It condenses and forms a dense region in the nucleus called a_____________ONE XSWITCHED OFFBARR BODY