ch 5.2 understanding inheritance

Ch. 5.2 Understanding Inheritance

Lesson 2 Reading Guide

1. What determines the expression of traits?

2. How can inheritance be modeled?

3. How do some patterns of inheritance differ from Mendel’s model?

Focus Questions

• Mendel concluded that

two factors—one from

each parent—control

each trait (called

chromosomes).

• Chromosomes are

made of coiled up DNA

• Genes are segments of

DNA for 1 trait.

Lesson 2

1. What determines the

expression of traits?

Lesson 2

• Remember that DNA stores genetic info.

• Alleles – different forms of a gene

– Each chromosome has 1 allele for every gene on it.

– Ex: Color of pea plant is found in 1 gene, alleles are purple and white

• The two chromosomes in an offspring cell may have the same or different alleles.

1. What determines the expression of

traits?

Lesson 2

Lesson 2

• Phenotype – how a trait physically appears

• Genotype – the 2 alleles (genes) that control the phenotype of a trait

1. What determines the expression of

traits?

A pea plant that is Yy

a. Genotype

b. Phenotype

45Genoty

pe

Phenotype

00

A pea plant that is green

a. Genotype

b. Phenotype

Genotype

Phenotype

00

45

The two alleles

a. Genotype

b. Phenotype

Genotype

Phenotype

00

45

Lesson 2

• Homozygous = same alleles (ex: RR, rr)

• Heterozygous = different alleles (ex: Rr)

1. What determines the expression of

traits?

What is the genotype? Rr

a. Homozygous

dominant

b. Homozygous

recessive

c. Heterozygous

45Homozy

gous dom

inant

Homozy

gous rece

ssiv

e

Hetero

zygous

0 00

What is the genotype? ww

a. Homozygous

dominant

b. Homozygous

recessive

c. Heterozygous

45Homozy

gous dom

inant

Homozy

gous rece

ssiv

e

Hetero

zygous

0 00

What is the genotype? CC

a. Homozygous

dominant

b. Homozygous

recessive

c. Heterozygous

45Homozy

gous dom

inant

Homozy

gous rece

ssiv

e

Hetero

zygous

0 00

What is the genotype? Yy

a. Homozygous

dominant

b. Homozygous

recessive

c. Heterozygous

45Homozy

gous dom

inant

Homozy

gous rece

ssiv

e

Hetero

zygous

0 00

Lesson 2

A Punnett square is a model used to predict possible genotypes and phenotypes of offspring.

2. How can inheritance be modeled?

Draw the following Punnett Squares

Yy x yy CC x cc

• Punnett Square Brain Pop

Lesson 2

A pedigree shows phenotypes of genetically related family members.

Male

female

Male

affected

Female

affected

2. How can inheritance be modeled?

Mrs. Calderon’s family Pedigree for Blue eyes (bb)

What color are Mrs. Calderon’s dad’s eyes?

Mrs.

Calderon

Mrs. Calderon’s family Pedigree for Blue eyes (bb)

a. Blue

b. Dark

c. Can’t tell from the

chart

60

Blue

Dark

Can’t te

ll fro

m th

e chart

0 00

How many brothers does Mrs. Calderon’s dad have?

Mrs.

Calderon

a. 1

b. 2

c. 3

d. 4

e. 5

f. 6

g. 7

h. 8

i. 9

j. 0

Mrs. Calderon’s family Pedigree for Blue eyes (bb)

601 2 3 4 5 6 7 8 9 0

0 0 0 0 000000

Does Mrs. Calderon carry the blue eye gene?

Mrs.

Calderon

a. Yes

b. No

c. Can’t tell from the

chart

Mrs. Calderon’s family Pedigree for Blue eyes (bb)

60

YesNo

Can’t te

ll fro

m th

e chart

0 00

Does Mrs. Calderon’s mom carry the blue eye gene?

Mrs.

Calderon

a. Yes

b. No

c. Can’t tell from the

chart

Mrs. Calderon’s family Pedigree for Blue eyes (bb)

60

YesNo

Can’t te

ll fro

m th

e chart

0 00

Lesson 2 Complex

• Sometimes traits appear to be blends of alleles.

Complex Patterns of Inheritance

3. How do some patterns of inheritance differ from Mendel’s model?

Lesson 2 Complex

3. How do some patterns of inheritance differ from Mendel’s model?

Complex patterns of inheritance

Incomplete dominance

Codominance

Polygenic Inheritance

Multiple alleles

Lesson 2 Complex

• Incomplete Dominance:when the offspring’s phenotype is a blend of the parents’ phenotypes.

3. How do some patterns of inheritance differ from Mendel’s model?

Lesson 2 Complex

• Codominance occurs when both alleles can be observed in a phenotype.

3. How do some patterns of inheritance differ from Mendel’s model?

Lesson 2

Polygenic Inheritance:

occurs when multiple genes determine the phenotype of a trait (ex: skin color, eye color).

3. How do some patterns of inheritance differ from Mendel’s model?

Lesson 2

3. How do some patterns of inheritance differ from Mendel’s model?

• Eye Color

Lesson 2

Multiple alleles: Some traits are determined by more than one allele;

ex: Human ABO blood types

3. How do some patterns of inheritance differ from Mendel’s model?

Lesson 2

• An organism’s environment can affect its phenotype.

• Some examples of environmental factors that affect phenotype are soil type that a flower is growing in or time of year that a butterfly develops.

Genes and the Environment

What type of inheritance is it when the

offspring’s phenotype is a blend of the parents’

phenotypes?

A. Incomplete

dominance

B. Codominance

C. Multiple alleles

D. Polygenic

inheritance

45Inco

mple

te d

omin

ance

Codomin

ance

Multi

ple alle

les

Polyge

nic in

heritance

0 000

What type of inheritance occurs when multiple genes determine the phenotype?

A. Incomplete

dominance

B. Codominance

C. Multiple alleles

D. Polygenic

inheritance

45Inco

mple

te d

omin

ance

Codomin

ance

Multi

ple alle

les

Polyge

nic in

heritance

0 000

What occurs when both alleles can be

observed in a phenotype?

A. incomplete dominance

B. homozygous

C. polygenic

D. codominance

45A. inco

mple

te d

omin

ance

B. hom

ozygo

us

C. polygenic

D. codom

inance

0 000

3. All inherited traits follow Mendel’s patterns of inheritance.

a. True

b. False

45Tru

eFa

lse

00

4. Scientists have tools to predict the form of a trait an offspring might inherit.

a. True

b. False

45Tru

eFa

lse

00