Mendel and the Gene Idea

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Slide 69

Pedigree Analysis

A pedigree is a family tree that describes the interrelationships of parents and children across generations

Inheritance patterns of particular traits can be traced and described using pedigrees

Slide 70

Fig. 14-15

Key

Male

Female

Affected

male

Affected

female

Mating

Offspring, in

birth order

(first-born on left)

1st generation

(grandparents)

2nd generation

(parents, aunts,

and uncles)

3rd generation

(two sisters)

Ww

ww

ww

Ww

Ww

ww

ww

Ww

Ww

ww

ww

Ww

WW

or

Widow’s peak

No widow’s peak

(a) Is a widow’s peak a dominant or recessive trait?

1st generation

(grandparents)

2nd generation

(parents, aunts,

and uncles)

3rd generation

(two sisters)

Ff

Ff

Ff

Ff

Ff

Ff

FF

or

ff

ff

ff

ff

ff

FF

or

Ff

Attached earlobe

Free earlobe

(b) Is an attached earlobe a dominant or recessive trait?

Slide 71

Fig. 14-15a

Key

Male

Female

Affected

male

Affected

female

Mating

Offspring, in

birth order

(first-born on left)

Slide 72

Fig. 14-15b

1st generation

(grandparents)

2nd generation

(parents, aunts,

and uncles)

3rd generation

(two sisters)

Widow’s peak

No widow’s peak

(a) Is a widow’s peak a dominant or recessive trait?

Ww

ww

Ww

Ww

ww

ww

ww

ww

Ww

Ww

ww

WW

Ww

or

Slide 73

Fig. 14-15c

Attached earlobe

1st generation

(grandparents)

2nd generation

(parents, aunts,

and uncles)

3rd generation

(two sisters)

Free earlobe

(b) Is an attached earlobe a dominant or recessive trait?

Ff

Ff

Ff

Ff

Ff

ff

Ff

ff

ff

ff

ff

FF

or

or

FF

Ff

Slide 74

Pedigrees can also be used to make predictions about future offspring

We can use the multiplication and addition rules to predict the probability of specific phenotypes

Slide 75

Recessively Inherited Disorders

Many genetic disorders are inherited in a recessive manner

Slide 76

The Behavior of Recessive Alleles