1. Sex Linkage and Sex detrmination

2. Test Cross unknown genotype homozygous recessive A mating between to determine genotype of an individual of unknown genotype and a homozygous recessive individual Example:C__ ccExample: C__ x cc CC = curly hair Cc = curly hair cc = straight hairC___c

3. Test Cross Possible results: C___cCcCcCcCc C C___ cCcCccor c

4. Sex Determination Sex Chromosomes XX chromosome - femaleXy chromosome - male

5. Sex Determination X XX X X XX X X yX y X yX y Xy X X

6. OtherOther Sex Determination Other sometimesThe Y chromosome sometimes does not dictate its maleness –Absence of a second X XY fruit fly is male XXY fruit fly is female

7. Environmental Environmental Sex Determination Environmental after fertilizationSex may be determined after fertilization temperatureDetermined by temperature during early embryonic development –Turtles produce more females at a higher temperature –Alligators and many lizards produce more males at a higher temperature

9. Sex-linked Traits sex chromosomes Traits (genes) located on the sex chromosomes Hemophiliacs (X-linked) Male Pattern Baldness (X-linked) Color-blindness (X-linked) Male Ear Hair (y-linked)

10. Sex-linked Traits Sex Chromosomes fruit fly eye color XX chromosome - female Xy chromosome - male

11. X N X N X n X N y Xn yXn y XNXN XNXN y XnXn N = normal n = Hemophilia

12. X N X N X n X N y Xn yXn y XNXN XNXN y XnXn Male Pattern Baldness N = normal n = Bald

13. X N X N X n X N y Xn yXn y XNXN XNXN y XnXn Colorblindness N = normal n = Colorblind http://www.toledo-bend.com/colorblind/Ishihara.html

14. X XX X X XX X X yX y X yX y X Xy X Y-linked Ear-Hair y = Ear Hair

15. Barr Bodies Barr discovered the Barr Body An inactive X chromosome – a darkly staining body in the nuclei of females Mary Lyon, identified the Barr body as an inactive X chromosome –Inactivation is random, with a 50 - 50 chance of inactivating the maternal or paternal X –The mammalian female is a genetic mosaic X Psome cells have the X P active X Msome have the X M active

16. Barr Bodies blackorangeFur coloration of calico cats is governed by two alleles (black and orange - multiple alleles ) Both attached to the same loci on a homologous pair of X chromosomes –In black fur cells – orange allele is inactive –In orange fur cells –black allele is inactive Explained in more detail at Barr Bodies and Gender Verification Barr Bodies and Gender Verification

17. X N X N X n X N y Xn yXn y XNXN XNXN y XnXn N = normal n = Hemophilia

18. Because: The human generation time is about 20 years. Humans produce relatively few offspring compared to most other species. Well-planned breeding experiments are impossible. Why do we need to study pedigrees to understand Mendelian inheritance in humans? Single gene traits studied using a pedigree:

19. Conventional Symbols for Human Pedigrees Normal male Normal female Normal, sex irrelevant or unknown Affected male Affected female Affected, sex irrelevant or unknown Mating Between relatives I II Last born siblings Sibling birth order from left to right

20. Pedigree Analysis Widow’s peak: dominant Attached ear lobe: recessive

21. Autosomal Recessive Pedigree Many people in these pedigrees were probably “carriers” - heterozygotes

22. Autosomal Dominant Pedigree No carriers

23. Karyotype A method of organizing the chromosomes of a cell in relation to number, size, and type.

24. Karyotyping Chromosomes can tell us –an unborn baby may have a genetic disorder –a person will be male or female Scientist can analyze –chromosomes in prenatal testing –diagnose specific diseases

25. Karyotyping

26. Karyotyping

27. FREQUENCY OF ABNORMALITY (%) Chromosome abnormality Spontaneous abortion StillbirthsLive birthsProbability of survival to term All5050.55 Trisomy 167.5--0 Trisomy 13,18,214.52.70.1415 XXX,XXY,XYY0.30.40.1575 All other trisomies13.80.9-0 45,X8.70.10.011 Triploidy 3n6.40.2-0 Tetraploidy 4n2.4--0 Structural Abnormalities2.00.80.345 http://www.carolguze.com/text/442-4-chromosome_abnormalities.shtml

28. Reciprocal Translocation: Philadelphia Chromosome

29. Abnormal chromosome in karyotype –46 chromosomes with a translocation between chromosome 9 and chromosome 22 (Philadelphia chromosome) –Most of chromosome 22 has been translocated onto the long arm of chromosome 9 –The small distal portion of the short arm of chromosome 9 is translocated to chromosome 22 Chronic Myelogenous LeukemiaTranslocation found only in Chronic Myelogenous Leukemia (CML) patients –the cells that produce blood cells for the body (the hematopoietic cells) grow uncontrollably, leading to cancer