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Genetics and Diversity II
Pedigrees and Adaptations
1
S1-1-14 Explain the inheritance of sex-linked traits
in humans and use a pedigree.
S1-1-08 Investigate adaptations of plant and animal
species which enhance reproductive success.
Vocabulary & People
Sex-linked
Natural Selection
Pedigree
Adaptation
Sex chromosome X carries genes that code for
traits other than gender.
Traits determined by genes on the X chromosome
are called sex-linked traits.
Hemophilia, colour-blindness, and baldness are
three common examples
x
y
x
x
• Inherits trait from mother
• Inherited from either parent
(give the X)
• Phenotype always shows gene
(no other allele to mask it)
• Needs two alleles to show
• Will pass to ALL daughters
Sex-linked traits are more
common in males
recessive trait
• One recessive allele: will not
show the trait - but is a
“carrier”
Y
Father = X
XY
Mother is a carrier
Mother = XX
¼ color-blind
male – 25%
XX
YX
XX
YX
½ disorder free
– 50%
¼ female carrier
– 25%
Pedigree: diagram representing the phenotype
history of a family.
Genotypes can be determined by analyzing the
trends of the pedigree
Symbols:
Male – square
Female – circle
Dominant trait – blank
Recessive trait – filled
A widow's peak hairline (W) is dominant over a
straight hairline (w):
What are the genotypes for
each person in this family?
Ww
W?
Ww
ww ww Ww
ww
ww
Ww
Ww
ww
W?
Natural selection is the gradual process of
traits becoming more common in a
population because the traits may improve
reproductive success of organisms in an
environment.
(It is a key mechanism of evolution)
Luck and timing has something to
do with it too…
Anything that
gives you an
advantage will
help you pass
that positive trait
on to offspring
disadvantage :
no offspring
“Only The Strong Survive”
Adaptation: a naturally selected trait that
enhances reproductive success.
• Can be physical or behavioural
How would big tail
feathers make him
more successful?
How would they
make him less
successful?
Examples of Adaptations
Behavioural
• caring for young
• mating calls
• dances
• fighting
Physical
• colours / camouflage
• size / shape
• pheromones
• multiple offspring
Those best able to modify their behavior or
those with positive mutations that improve
their survival and reproductive success pass
on these traits to future offspring
Think of adaptations that have evolved to
help an organism (including humans)
survive its environment and reproduce.
CAN YOU ANSWER THESE QUESTIONS?
S1-1-14:
What is a pedigree and how is it used to track
inheritance of a trait?
S1-1-08:
What are some ways plants and animals improve their
chance to reproduce?
Vocabulary & People
Sex-linked
Natural Selection
Pedigree
Adaptation