{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Wk 6_Ch8.1-2_XY chromo biology

Wk 6_Ch8.1-2_XY chromo biology - LS 4 Wk 6 7 Ch 8.1-5 X/Y...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
LS 4 Wk 6 + 7 -- Ch 8.1-5 X/Y Chrom Biology, Human Karotype, Chrom Disorders Ch 8.1 Yilan Shi Dosage Compensation of X-Linked Genes Drosophila: males INCREASE X chromosome activity by acetylation/silencing DNA C. Elegans (???)- females decrease EACH X-chromosome activity by half. Mammals: X-chromosome is INACTIVATED randomly in early cell division o Chromosome condense at site: XIC o Makes “bend” in metaphase (of mitosis) visible o Chromosomes w/ deletions at this site = unactivated= cause prb’s o Xist = X-inactivation-specific transcript = only transcribed part of inactivated part of X chrom. not exon, it’s only a structure RNA (not protein after splicing, b/c splicing cuts off ORF) 2 Results of X-inactivatn 1. Female = mosaic for X-linked genes in somatic cells. B/c X-chrom inactivated randomly, ea body cell might have diff X turned off esp. if a F is heterozygous for an X-linked allele. 2. Dosage compensation for females equal copies of X-linked genes in M & F. Ex’s: Calico cat Marsupials= SELECTIVE X-inactivatn—Inactivate FATHER’s X Human female sweat glands Exceptions: Some genes on inactivated X are NOT silenced & have homologous genes on Y chrom! Tips of arms not silenced – “ Telomeric region X + Y share homologous pairs of alleles CROSSOVER! Genes in “ Pseudoautosomal region ” (PARp) follow AUTOSOMAL inheritance pattern , but physically on X/Y 15% active genes on silent X active genes in lrg blocks in short arm tips Suggest farther away from Xist= more gene activity? PAR on tips of chromosomal arms !
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Activated genes on inactive X have transcription levels 15-50% explains why F hemop carriers = diff exprsn Evolution of Sex Chromosomes!
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern