Human Sex Chromosomes & linked Genes
• Human chromosome condition: diploid(2n) = 46.
• 44 (22 pair) = autosomes• 2 (1 pair) = sex chromosomes
(Y chromosome = SEX IS MALE – it is physically missing part of the chromosome = less information)
46, XX Normal Female 0.511*
46, XY Normal Male 0.489*
45, XO Female 1/5,000
47, XXY Male 1/700
‘Y’ chromosome = SEX IS MALE
Sex linkage is when a gene is carried on one of the sex
chromosomes.• Sex linked traits
– Are usually recessive (some are not)
– Are usually on the X Chromosome
• E.g.Hemophilia and Color Blindness
= XBXB = normal female
= XBXb = normal female “carrier”
= XbXb = affected female
= XBY = normal male
= XbY =affected male
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HOW CAN YOU DETERMINE IF FEMALE FLY IS A ‘CARRIER’ OF
WHITE EYE GENE OR NOT?
DO A TEST CROSS WITH A WHITE EYED MALE