Sex Linkage (Leaving Cert Biology): Flashcards
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Sex linkage definition
Sex linkage definition
Gene located on a sex chromosome
Female sex chromosomes
Female sex chromosomes
XX
Male sex chromosomes
Male sex chromosomes
XY
Red-green colour blindness trait
Red-green colour blindness trait
Inability to distinguish between red and green
Haemophilia trait
Haemophilia trait
Inability to form blood clots properly
Why are sex-linked traits more common in males?
Why are sex-linked traits more common in males?
Males need only one recessive gene on X to express trait
Genes needed for females to express sex-linked trait
Genes needed for females to express sex-linked trait
Two recessive genes (one on each X chromosome)
Carrier female definition
Carrier female definition
Heterozygous female with one normal and one abnormal allele
Male with normal vision genotype (N=normal)
Male with normal vision genotype (N=normal)
XN Y
Female with normal vision genotype
Female with normal vision genotype
XN XN
Female carrier genotype (N=normal, n=colour blind)
Female carrier genotype (N=normal, n=colour blind)
XN Xn
Male with colour blindness genotype
Male with colour blindness genotype
Xn Y
Female with colour blindness genotype
Female with colour blindness genotype
Xn Xn
Chromosome with most sex-linked genes
Chromosome with most sex-linked genes
X chromosome
Offspring % from carrier female × normal male cross
Offspring % from carrier female × normal male cross
25% each: normal female, carrier, normal male, colour blind male