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Pedigrees and AdaptationsGenetics and Diversity II

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 PedigreeNatural Selection 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

• Inherits trait from mother (give the X)• Phenotype always shows gene (no other allele to mask it)

• Will pass to ALL daughters

xy

xx

• Inherited from either parent

• Needs two alleles to show recessive trait

• One recessive allele: will not show the trait - but is a “carrier”

Sex-linked traits are more common in males

Father = XY

Mother = XX

XYXX

X

X

X

X

Y

Y

X

X

½ disorder free – 50%

¼ color-blind male – 25%

¼ female carrier – 25%

Mother is a carrier

Pedigree: diagram representing the phenotype history of a family.

Symbols:Male – squareFemale – circle Dominant trait – blankRecessive trait – filled

Genotypes can be determined by analyzing the trends of the pedigree

A widow's peak hairline (W) is dominant over a straight hairline (w):

ww

W

ww ww ww

wwW W

W

W

WW

w

w

w w

w

?

?

What are the genotypes for each person in this family?

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.

How would big tail feathers make him more successful?

How would they make him less successful?

• Can be physical or behavioural

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 PedigreeNatural Selection Adaptation