I will review DiHybrid Crosses & then learn Sex-Linked Crosses ISN p.152 MT 16, The Genetics of Life Thurs 02.21.13 TOPIC: MY GOAL: GET ON TSSK I will review DiHybrid Crosses & then learn Sex-Linked Crosses Turn to your DiHybrid Cross HW…

Bottom of ISN p. 152 – Work it! T T P p x T t P P TP Tp TP Tp TP tP Genotype Phenotype TP Tp TP Tp TTPP=4 TTPp=4 TtPP=4 TtPp=4 TP tP TTPP TTPp TtPP TtPp Tall, Purple = 16

DiHybrid Cross TOP of ISN p. 152 – Work it! T T P p x T T P P TP Tp TP Tp Genotype Phenotype TP TTPP TTPp TTPP=8 TtPp=8 Tall, Purple = 16

Your 2nd Job Today ISN page155 WRITE in ANSWERS X or Y X or Y, X XY, XX You will use the ‘key’ provided to work the Sex Linked Punnett Square on ISN p.154 after I explain…

Autosomes vs Sex Chromosomes Notes, ISN p.155 Autosomes vs Sex Chromosomes Sex Xsomes = Xsome pair #23 XX = F XY = M Autosomes = Xsome pairs #1-22 Amniocentesis 5

MALES determine the sex of the offspring! 46 Chromosomes total in humans! 2 are sex xsomes: XX or XY Eggs = X or X sperm - X or Y Sperm determines sex of the offspring X X X Y GIRL BOY

Sex Linked Traits Traits found ONLY on the Sex Xsomes  specifically the X EXAMPLES: Colorblindness… Hemophilia… Muscular Dystrophy… Traits found on Autosomes – the first 22 pair - are written as letters like Dd or FF (dimples & freckles) But when a trait is on the Sex Xsome, you change the way you write the gene… 

How do you represent Sex-Linked genes? c C C X X X Y As a superscript: The genes are attached or LINKED to the X sex chromosomes! That’s why they are written as superscripts. No disorders are linked to the ‘Y’ xsomes because it is so small

What is a “Carrier”? Why are they “normal”? Notes ISN page 155 What is a “Carrier”? Why are they “normal”? Carrier = only F = do NOT exhibit trait, just carry it & MIGHT pass it on XYor XY C c c C C C c c X X or X X or X X So why can’t men be carriers AND why do more men have Sex-Linked Genetic Disorders???? c c c X X X Y

Sex Linked Punnett Square Cross a Heterozygous Normal Color Vision Female with a colorblind male. XCXc x XcY

XCXc x XcY Xc Y XC Xc XC Xc Xc Xc Xc Y XC Y Genotype Phenotype ? 1 F, Carrier = 25% XC Xc Xc Xc Xc Xc= Xc Y 1 F, CB = 25% XCY= 1 M, Normal = 25% Xc Y Xc Y= XC Y 1 M, CB = 25% ?

Your 3rd Job Today ISN page154 WORK the 2 Sex Linked Punnett Squares 1st = Color Vision 2nd = Hemophilia Use the Keys on ISN p.155

XcY x XCXC XC Xc Y XC Xc XC Y XC Xc XC Y XC Genotype Phenotype 2 Carrier are NORMAL! = 50% XC Xc XC Y XC XC Y = 2 M, normal vision = 50% XC Xc XC Y XC % children w/ normal vision??? 100%

XhXh x XHY Xh XH Y XH Xh Xh Y Xh Y XH Xh Genotype Phenotype 2 Carrier = 50% Xh XH Xh Xh Y Xh Y = 2 M, hemophilia = 50% Xh Y 50/50 chance children will be normal XH Xh

Be the change you wish to see in the world Study a bit each night.. HOMEWORK Be the change you wish to see in the world 15 15