sex linkage
geneticinformation for sex is carried on 2 sex chromosomes
females have 2 x chromosomes xx and males have one X
chromosome and one Y chromosome XY
x x
x xx xx hence probability of male or female is equal1501
Y XY XY
sex linked genes geneslocated on one of the sex chromosomes X or Y
Ychromosome is much smaller than X chromosome so most alleles
carried on X chromosome x linked
Menonlyhave one X chromosome so will only inherit one allele for these
genes whereas females will inherit two
this means that if men inherit a recessive allele which causes a
disease for a gene found on the X chromosomethey will have the disease
but women who inherit recessive allele will just be a carrier since they have
anothe X chromosome with the dominant allele
for women to have x linked diseases they must inherit twodisease
alleles so both parents would have to be diseased
examplesof sex linked disorders include
haemophilia and red green blindness
Pedigree charts
show an inherited trait characteristic in a group
of related individuals
be.gl
Autosomal linkage
the 22 chromosomes other than sex chromosomes are calledautosomes
positionof a gene on a chromosome Locus loci of 2 different genes on the
same chromosome linked
2 or more genescarried on same autosome autosomallinkage
if 2 different alleles are foundon 2 different chromosomes then there
are a possiblecombinations of alleles but if the 2different alleles are on
the same chromosomethen there are only two possiblecombinationsofalleles
only 1 homologous pairneeded when linked for all 4 alleles to be present
whereas 2 required when not linked
not linked blinked
geneticinformation for sex is carried on 2 sex chromosomes
females have 2 x chromosomes xx and males have one X
chromosome and one Y chromosome XY
x x
x xx xx hence probability of male or female is equal1501
Y XY XY
sex linked genes geneslocated on one of the sex chromosomes X or Y
Ychromosome is much smaller than X chromosome so most alleles
carried on X chromosome x linked
Menonlyhave one X chromosome so will only inherit one allele for these
genes whereas females will inherit two
this means that if men inherit a recessive allele which causes a
disease for a gene found on the X chromosomethey will have the disease
but women who inherit recessive allele will just be a carrier since they have
anothe X chromosome with the dominant allele
for women to have x linked diseases they must inherit twodisease
alleles so both parents would have to be diseased
examplesof sex linked disorders include
haemophilia and red green blindness
Pedigree charts
show an inherited trait characteristic in a group
of related individuals
be.gl
Autosomal linkage
the 22 chromosomes other than sex chromosomes are calledautosomes
positionof a gene on a chromosome Locus loci of 2 different genes on the
same chromosome linked
2 or more genescarried on same autosome autosomallinkage
if 2 different alleles are foundon 2 different chromosomes then there
are a possiblecombinations of alleles but if the 2different alleles are on
the same chromosomethen there are only two possiblecombinationsofalleles
only 1 homologous pairneeded when linked for all 4 alleles to be present
whereas 2 required when not linked
not linked blinked
