The document discusses human genetics and chromosomal disorders. It describes how genomes contain genetic information, and the human genome contains 23 pairs of chromosomes including 22 autosomal chromosome pairs and one pair of sex chromosomes. It explains recessive and dominant disorders such as phenylketonuria (PKU), cystic fibrosis, dwarfism, and Huntington's disease. It also discusses sex-linked disorders including red-green color blindness, hemophilia, and Duchenne muscular dystrophy. Finally, it summarizes chromosomal disorders caused by nondisjunction, including Down syndrome, Turner syndrome, and Klinefelter syndrome.

1. The Human GenomeFrom Peas and fruit flies to humans…

3. What is a genome???All the genetic information (genes) that make up an organism

4. What makes us human?Analyze human chromosome…KarotypePicture of all the chromosomes in an organismAutosomesCHROMOSOMES 1-44 (pairs 1-22)Autosomal chromsomesSex chromosomesDetermine a person’s sex (male XY or female XX)Chromosome 45 and 46 (set 23)

6. Pedigree ChartsShows relationships within a familyGenetic counselors use these to infer the genotypes of family membersLook at each generation different symbols used

8. Disorders can be recessive or dominant

10. Recessive disordersDisorder phenylketonuria (PKU)Caused by an autosomal recessive allele on chromosome 12People with this disorder lack the enzyme to break down phenylalanine (amino acid found in milk and many other foods)In newborns, this causes a build up of phenylalanine in tissues during the first few years of life and lead to mental retardationNewborns are commonly tested for PKU and then put on a low phenylalanine diet if they have the disorder

11. Autosomal Recessive AlleleTay-Sachs DiseaseRecessive allele in Jewish families of central and eastern Europe ancestryLack the enzyme to break down lipids in neural cellsLipid accumulation in brain cellsLeads to nervous system break-down and death in the first few years of life

12. Autosomal Recessive DisordersCystic FibrosisDo not have the gene that regulates mucus productionExcess mucus in lungs, digestive tract, and liverIncreased susceptibility to disordersLung transplants usually needed after childhood

13. Autosomal Dominant DisordersYou will express disorder if you are homozygous or heterozygous dominant for that traitYou also have higher chances of passing onto your childrenDwarfism (achondroplasia)Huntington’s DiseaseNervous system disorder

14. Co-Dominant Alleles DisordersSickle cell anemia1/500 African Americans have the disorderCo-dominant alleleCauses blockages in blood vessels, preventing oxygen from getting to other cells and tissuesBeneficial in central and east Africa because it helped destroy malariaIf you had SCA, your body would destroy the sickle cells to protect itself and in the process, destroy the malaria parasite as well

16. Sex-Linked DisordersMany sex-linked genes are found on x-chromosomeMany genetic disorders are sex-linkedMales have just ONE x chromosome, so whatever the X chromosome is carrying (dominant or recessive) will be expressedFathers can pass it to their daughters and the disorder can show up in the daughters sons

17. Sex-linked DisordersRed-green Color-blindness 1/10 men1/100 womenHemophiliaTwo important genes on x-chr control blood clottingPerson with disorder can die from minor cuts Recessive allele in either gene can cause itDuchenne Muscular DystrophyCaused by defective version of a gene for a muscle proteinProgressive weakening and loss of skeletal muscle1/3000 males

18. X-chromosome InactivationFemales have XX and males have XY…is the second X chr in females needed??British Geneticist Mary Lyon In female cells, one x-chromosome is randomly shut off…this “shut off” chromosome is called a Barr BodyDifferent X-chrm are switched off in different cellsGenerally not found in males b/c X-chrm needs to be ACTIVEOccurs in other mammals as well

19. Barr bodies in catsGene that controls color of coat spots is located on the X-chrmIn a female, one X-chrm may have the allele for orange spots and the other X-chrm may have the allele for black spotsDifferent cells in different parts of the cat’s body are switched off= different colored spots on different parts of the cat…mix or orange and black spotsMales only have ONE active X-chrm…therefore, will they have different colored spots?No…only psots of ONE color (b/c on ONE active X)This is one way to determine the sex of a cat…cat with black AND orange spots is almost always certainly female

21. Chromosomal DisordersMechanics of meiosis (where we separate chromosomes) is usually pretty goodBut nobody’s perfect…mistakes happen….Most common problem…Nondisjunction: when homologous chromosomes fail to separate properlyLiterally means “not coming apart”If this occurs, ABNORMAL #s of chromosomes may find their way into gametes and a disorder of chromosome number may result

22. NondisjunctionIf one of the gametes with an ABNORMAL # ends up getting fertilized, MAJOR problems!!!Trisomy: “three bodies”Occurs when an autosomal chromosome fails to separate during meiosisWhen do chrm separate?Anaphase I and Anaphase 2One gamete ends up with an extra copy of a chromosome and then the fertilized zygote ends up with 3 copies of a chrm instead of 2Example: Downs Syndrome

25. Down SyndromeExtra copy of chromosome 211/800 baby’s are born with this disorderProduces mild to severe retardationIncreased susceptibility to diseases, slower development, and higher frequency of birth defectsHow can one little extra copy cause so many problems?Scientists are still trying to figure that out…now that they have used gene mapping and identified all the genes on chromosome 21, they can begin experimenting on this problem

26. Sex Chromosome DisordersWhat happens if nondisjunction happens to the sex chromosomes???We know we need at least one X chromosome….No embryos have been found with just a Y chromosome so we now X chrm contains vital genes!Turners SyndromeFemales receive only one X chromosomeKarotype 45, XUnable to reproduce, sex organs do not develop at pubertyKlinefelters SyndromeMales receive an extra X chromosomeKarotype 47, XXYPrevents individuals from reproducingCases of individuals with XXXY and XXXXYY chromosome contains “sex determining region” SDR, which gives male characteristics and developmentIf region is absent, embryo develops into female

27. Turner’s Syndrome

29. What about an extra Y?Males with 47, XYY produce more male hormones and express a more expressive behaviorMore testosterone=more aggressive behaviorHigher number of men in prison for violent crimes have XYY however there is a large population of men with XYY that do not exhibit (or at least act upon) this aggressionCannot use this as an excuse for aggressive behavior or else criminals would be pleading an extra Y instead of insanity :-o