End Show Slide 1 of 31 Copyright Pearson Prentice Hall Biology.

End Show

Slide 1 of 31

Copyright Pearson Prentice Hall

Biology

End Show

Slide 2 of 31


11-3 Exploring Mendelian Genetics11–3 Exploring Mendelian Genetics

End Show

11–3 Exploring Mendelian Genetics

Slide 3 of 31


Independent Assortment

To determine if the segregation of one pair of alleles affects the segregation of another pair of alleles, Mendel performed a two-factor cross.


End Show


Slide 4 of 31



The Two-Factor Cross: F1

Mendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy).

RRYY x rryy

All of the F1 offspring produced round yellow peas (RrYy).

End Show


Slide 5 of 31



The alleles for round (R) and yellow (Y) are dominant over the alleles for wrinkled (r) and green (y).

End Show


Slide 6 of 31



The Two-Factor Cross: F2

Mendel crossed the heterozygous F1 plants (RrYy) with each other to determine if the alleles would segregate from each other in the F2 generation.

RrYy × RrYy

End Show


Slide 7 of 31



The Punnett square predicts a 9 : 3 : 3 :1 ratio in the F2 generation.

Represents:


End Show


Slide 8 of 31


The alleles for seed shape segregated independently of those for seed color. This principle is known as independent assortment.

Genes that segregate independently do not influence each other's inheritance.


End Show


Slide 9 of 31


The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes.

Independent assortment helps account for the many genetic variations observed in plants, animals, and other organisms.


End Show


Slide 10 of 31


A Summary of Mendel's Principles


• Genes are passed from parents to their offspring.

• If two or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive.

End Show


Slide 11 of 31


• In most sexually reproducing organisms, each adult has two copies of each gene. These genes are segregated from each other when gametes are formed.

• The alleles for different genes usually segregate independently of one another.


End Show


Slide 12 of 31


Beyond Dominant and Recessive Alleles

Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.

End Show


Slide 13 of 31



Incomplete Dominance

When one allele is not completely dominant over another it is called incomplete dominance.

In incomplete dominance, the heterozygous phenotype is between the two homozygous phenotypes.

End Show

Slide 14 of 31



A cross between red (RR) and white (WW) four o’clock plants produces pink-colored flowers (RW).


WW

RR

End Show


Slide 15 of 31



Codominance

In codominance, both alleles contribute to the phenotype.

In certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers.

Heterozygous chickens are speckled with both black and white feathers. The black and white colors do not blend to form a new color, but appear separately.

End Show


Slide 16 of 31



Multiple Alleles

Genes that are controlled by more than two alleles are said to have multiple alleles.

An individual can’t have more than two alleles. However, more than two possible alleles can exist in a population.

A rabbit's coat color is determined by a single gene that has at least four different alleles.

End Show


Slide 17 of 31



Different combinations of alleles result in the colors shown here.

Full color: CC, Ccch, Cch, or CcChinchilla: cchch, cchcch, or cchcHimalayan: chc, or chchAIbino: cc

KEY

C = full color; dominant to all other alleles

cch = chinchilla; partial defect in pigmentation; dominant to ch and c alleles

ch = Himalayan; color in certain parts of the body; dominant to c allele

c = albino; no color; recessive to all other alleles

End Show


Slide 18 of 31

End Show


Slide 19 of 31



Polygenic Traits

Traits controlled by two or more genes are said to be polygenic traits.

Skin color in humans is a polygenic trait controlled by more than four different genes.

End Show


Slide 20 of 31

LE 14-12

aabbcc Aabbcc AaBbcc AaBbCc AABbCc AABBCc AABBCC

AaBbCcAaBbCc

20/64

15/64

6/64

1/64

Fra

ctio

n o

f p

rog

eny

End Show

- or -Continue to: Click to Launch:

Slide 21 of 31


11–3

End Show

Slide 22 of 31


11–3

In a cross involving two pea plant traits, observation of a 9 : 3 : 3 : 1 ratio in the F2 generation is evidence for

a. the two traits being inherited together.

b. an outcome that depends on the sex of the parent plants.

c. the two traits being inherited independently of each other.

d. multiple genes being responsible for each trait.

End Show

Slide 23 of 31


11–3

Traits controlled by two or more genes are called

a. multiple-allele traits.

b. polygenic traits.

c. codominant traits.

d. hybrid traits.

End Show

Slide 24 of 31


11–3

In four o'clock flowers, the alleles for red flowers and white flowers show incomplete dominance. Heterozygous four o'clock plants have

a. pink flowers.

b. white flowers.

c. half white flowers and half red flowers.

d. red flowers.

End Show

Slide 25 of 31


11–3

A white male horse and a tan female horse produce an offspring that has large areas of white coat and large areas of tan coat. This is an example of

a. incomplete dominance.

b. multiple alleles.

c. codominance.

d. a polygenic trait.

End Show

Slide 26 of 31


11–3

Mendel's principles apply to

a. pea plants only.

b. fruit flies only.

c. all organisms.

d. only plants and animals.

END OF SECTION

End Show Slide 1 of 31 Copyright Pearson Prentice Hall Biology.

Documents

Transcript of End Show Slide 1 of 31 Copyright Pearson Prentice Hall Biology.