DNA IDENTITY AND DISEASE

Y-chromsome ANALYSIS:By the end of this lecture aim is to :1) Evaluate the use of Y -chromosome markers to identify individuals 2) Discuss how alterations to the T-chromosome can be linked to pathologies3) explain how the amelogenin is used to differentiate the males and females5)describe how Y-STR and Y-SNP are being used to type individuals for genealogy studiesSTR DETECTION:-needs a detection method which can distinguish 2-4 bases difference-capillary electrophoresisY CHROMOSOME structure1) Contains 78 protein coding genes2) encodes 27 proteins3) HEMIZYGOUS ( has no partner)DISORDERS ASSOCIATED WITH Y-CHROMOSOME:1) Infertility ( De novo deletion of q-arm ( long arm) , sometimes due to recombination.2) rare single gene abnormality in USP9YY- chromosome azoospermia:1) infertility 2) Y chromosome infertility by azoospermia (there is Mild, severe and moderate types of azoospermia: Syndromes related to Y chromosome1) 46, XX testicular disorder of sex developmenttranslocation of the SRY gene onto an X chromosome. Foetus with affected X chromosome will develop as a MALE2) 48, XXYY syndromeExtra X and Y chromosomes in a male's cells. Interferes with male sexual development and reduces levels of testosterone3) 47, XYY syndromeOne X chromosome and 2 Y's in each cell for a total of 47 chromosomes. Associated with tall stature, learning difficulties 6) 46, XY/47, XYY mosaicismY-chromosome in FORENSICS:Y-chromosome typing:1) sexual assault2) amelogenin deficient males3) paternity testing4) missing persons5) migration and evolutionary studies6) historical and geneological researchDifferential extraction of samples Remove a portion of the mixed stain Perpetrator’s sperm mixed with victim’s epithelial cells Add SDS, EDTA and proteinase K (cell lysis buffer),Incubate at 37 degrees and centrifuge sperm pellet REMOVE supernatant = FEMALE FRACTION Add SDS, EDTA and proteinase K + DTT DTT lyses sperm heads = sperm pellet = MALE FRACTION Differentiating between males and female samples: 1) large amounts of cells- chromosome analysis ( KARYOTYPING)2) bodies ( small particles seen in serology)3) typing for genes specific to Y-chromosome ( NRY or MSY region)4) Y-STR 5) Y-SNP6) Genes which vary between X and Y chromosome e.g. AmelogeninWhat is Amelogenin?Gene occurs in male and female for X chromsome - 103 bp for Y chromsome- 109 bp Why do male profiles have both 103 and 109 bp fragments?Ans: Because they have X and Y chromosomes together whereas females only have XX chromosomesThe structure of Amelogenin (AMEL) , the Y -chromosome is much smaller (50Mb) than the X chromosome (154 Mb). Y chromosome markers:1) Amelogenin is useful to determine if a sample is from a female or male 2) Other Y chromosome STR markers are utilised to identify individuals3) for mixed samples where the DNA from the male is virtually undetectable ( sexual assault) - y chromosome testing may yield a profileY-STRDYS38911DYS385DYS393DYS19Y-SNPsingle nucleotide polymorphisms (SNP)very low mutation rates for example: M11, M119 , M130 etc and SRY+ 465 and TATGeneology testing1) significant amount of interest by public to find out about their ancestors '' who do you think you are''2) surname mapping can be linked to the Y chromosome: