Transcript X –Linked Traits

Pedigrees
Show how traits are passed on in a family
= Female
= Male
•See purple booklet after page 16 OR blue page 57 for pedigree
symbols (these are on your diploma exam data sheet).
•Line down from a horizontal line indicates offspring.
•Oldest offspring always on the left
•Affected individuals are shaded in
•Heterozygous individuals half shaded in (sometimes)
Modes of Inheritance
see purple pages 15, 16
Autosomal
Recessive
•aa = affected
•May skip 1 or more
Generations
(recessive trait
hidden for
generations)
•2 unaffected may
have affected
•2 affected will have
all children affected
Autosomal
Dominant
•Aa or AA = affected
•Affected need only
have 1 affected
parent
•Affected (Aa)
parents can have
unaffected children
(aa)
Sex Linked
•Males mostly affected
•Males inherit sexlinked trait from
mothers
•Girls must have
affected fathers
Albinism
Must be autosomal
recessive. For this
condition, affected
individuals are
homozygous
recessive – lack
enzyme to produce
melanin.
Recessive?
Dominant?
Sex-linked?
Pedigree Analysis
What
is
this
pedigree
showing?
Why is inbreeding not recommended?
Chance of
recessive
condition
showing up
in offspring
is increased!
Lets’ draw a pedigree for Jason’s family
•
•
•
•
•
•
•
•
•
Sister (28) – unaffected
Jason (27) - unaffected
Brother (25) – affected
Identical twin brothers
(18) – unaffected
Mother (46) –
unaffected
Father (45) – affected
Paternal sister (43) –
affected
Paternal grandmother
(77) – unaffected
Paternal grandfather
(79) - affected
Jason
Pedigree Questions
Today
• Go to…purple - after page 16 – page 2 (Tay-Sachs
disease)…
• orange page 48 – 50
• Together: start page 51…
All pedigree questions:
• Purple: page 2 – 5 (after page 16)
• Orange: pages 48 - 55
• Blue: page 33 – 36
All X-linked Questions:
• Orange: pages 36 – 41
• Blue: page 48
All pedigree questions:
• Purple: page 2 – 5 (after page 16)
• Orange: pages 48 - 55
• Blue: page 33 – 36
• Pedigree sheet