Transcript Royal family pedigree following the hemophilia allele

Pedigrees
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A pedigree is a diagram of family relationships
that uses symbols to represent people and lines
to represent genetic relationships.
In a pedigree, squares show males and circles
show females. Horizontal lines connecting a
male and female show mating. Vertical lines
extending down from a couple show their
children. Subsequent generations are written
underneath the parental generations.
it is customary to shade in the symbol of all
individuals that possess the trait of interest.
Royal family pedigree
expressing the hemophilia allele
QuickTime™ and a
decompressor
are needed to see this picture.
My pedigree shows that:
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The allele for Huntington’s Disease is:
 Sex
linked on the Y
 Sex linked on the X
 Autosomal dominant (caused by a
dominant allele)
 Autosomal recessive (caused by a
recessive allele)
Sex-linked traits
22 of your 23 pairs of homologous
chromosomes act the same regardless
of your sex- autosomal.
 The 23rd pair are sex chromosomes
 Females are XX (inherit an X from
each parent)
 Males are XY (inherit X from mom and
Y from dad).
 Genes found on either the X or Y
chromosomes are called sex-linked.
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Sex-linked cont.
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There are over a 1,000 X-linked traits; Ylinked traits are rare and mostly deal with
sperm production.
In woman, a recessive allele on one X can
be masked by a dominant allele on the
other X.
In men, recessive alleles on the X are
always expressed since there is not a
corresponding allele on the Y.
This explains why woman are usually
carriers of X-linked traits, but rarely
express them.
For more info:
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http://anthro.palomar.edu/biobasis/bio_4.htm
Autosomal Dominant
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For those traits exhibiting
dominant gene action:
affected individuals have at
least one affected parent
the phenotype generally
appears every generation
two unaffected parents only
have unaffected offspring
The following is the pedigree
of a trait controlled by
dominant gene action.
QuickTime™ and a
decompressor
are needed to see this picture.
Autosomal Recessive
For those traits exhibiting
recessive gene action:
 unaffected parents can
have affected offspring
 affected progeny are
both male and female
The following is the
pedigree of a trait
controlled by recessive
gene action.
QuickTime™ and a
decompressor
are needed to see this picture.