Chapter11 Section01 Edit Oct 14th

8/3/2019 Chapter11 Section01 Edit Oct 14th

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Copyright Pearson Prentice Hall

biology


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11-1 The Work of Gregor Mendel11-1 The Work of GregorMendel


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11-1 The Work of Gregor Mendel

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Gregor Mendels PeasGenetics is the scientific study of heredity.

Gregor Mendel worked with ordinary garden peas.

Gregor Mendels Peas


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Gregor Mendels Peas

Mendel knew that

the male part ofeach flowerproduces pollen,

(containingsperm).

the female partof the flowerproduces eggcells.


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Gregor Mendels Peas

During sexual reproduction, sperm and egg cells joinin a process called fertilization.

Fertilization produces a new cell.


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Gregor Mendels Peas

Pea flowers are self-pollinating.

Sperm cells in pollen fertilize the egg cells in thesame flower.

The seeds that are produced by self-pollinationinherit all of their characteristics from the single plantthat bore them.


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Gregor Mendels Peas

Mendel had true-breeding pea plants that, if allowedto self-pollinate, would produce offspring identical tothemselves.

Mendel wanted to produce seeds by joining male and

female reproductive cells from two different plants.

He cut away the pollen-bearing male parts of theplant and dusted the plants flower with pollen from

another plant.


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Gregor Mendels Peas

This process iscalled cross-pollination.

Mendel was ableto produce seedsthat had twodifferent parents.


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Genes and Dominance

Genes and Dominance

A trait is a specific characteristic that varies fromone individual to another.


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Genes and Dominance

Genes and DominanceMendel studied seven pea plant traits, each with twocontrasting characters.


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Genes and Dominance

Each original pair of plants is the P (parental)generation.

The offspring are called the F1, or first filial,generation.

The offspring of crosses between parents withdifferent traits are called hybrids.

The F1 hybrid plants all had the character of only oneof the parents.


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Genes and Dominance

Mendels F1 Crosses on Pea Plants


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Genes and Dominance

Mendels Seven F1 Crosses on Pea PlantsMendels F1 Crosses on Pea Plants


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Genes and Dominance

Mendel's first conclusion was that biologicalinheritance is determined by factors that are passedfrom one generation to the next.

Today, scientists call the factors that determine traits

genes.

Th W k f G M d l G d D i


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Genes and Dominance

Each of the traits Mendel studied was controlled byone gene that occurred in two contrasting forms thatproduced different characters for each trait.

The different forms of a gene are called alleles.

Mendels second conclusion is called the principle of

dominance.

11 1 Th W k f G M d l G d D i


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Genes and Dominance

What is the principle of dominance?



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Genes and Dominance

The principle of dominance states that

some alleles are dominant and others arerecessive.



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Genes and Dominance

An organism with a dominant allele for a trait willalways exhibit that form of the trait.

An organism with the recessive allele for a trait willexhibit that form only when the dominant allele for

that trait is not present.

11 1 Th W k f G M d l S ti


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Segregation

What happens during segregation?

11 1 The Work of Gregor Mendel Segregation


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Segregation

Segregation

Mendel crossed the F1 generation with itself toproduce the F2 (second filial) generation.

The traits controlled by recessive alleles reappearedin one fourth of the F2 plants.

11 1 The Work of Gregor Mendel

Segregation


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Mendel's F2

Generation

PGenerationF1Generation

Tall Tall Tall Tall Tall TallShort Short

F2Generation

Segregation



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Segregation

Mendel assumed that a dominant allele had maskedthe corresponding recessive allele in the F1generation.

The trait controlled by the recessive allele showed up

in some of the F2 plants.



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Segregation

The reappearance of the trait controlled by therecessive allele indicated that at some point the allelefor shortness had been separated, or segregated,from the allele for tallness.



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Segregation

Mendel suggested that the alleles for tallness andshortness in the F1 plants segregated from eachother during the formation of the sex cells, orgametes.

11-1 The Work of Gregor Mendel Segregation


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Segregation

When each F1 plant flowers andproduces gametes, the two allelessegregate from each other so that

each gamete carries only a single copyof each gene.

Therefore, each F1 plant produces two

types of gametesthose with theallele for tallness, and those with theallele for shortness.

11-1 The Work of Gregor Mendel Segregation


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Segregation

Alleles separate during gamete formation.


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11-1
http://resources/ch11_sectn01_quiz.qtbhttp://resources/ch11_sectn01_quiz.qtbhttp://resources/ch11_sectn01_quiz.qtb


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Gametes are also known as

a. genes.

b. sex cells.

c. alleles.

d. hybrids.


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The offspring of crosses between parents with

different traits are called

a. alleles.

b. hybrids.c. gametes.

d. dominant.


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In Mendels pea experiments, the male gametes

are the

a. eggs.

b. seeds.c. pollen.

d. sperm.


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In a cross of a true-breeding tall pea plant with a

true-breeding short pea plant, the F1 generationconsists of

a. all short plants.

b. all tall plants.

c. half tall plants and half short plants.

d. all plants of intermediate height.


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11-1

If a particular form of a trait is always present

when the allele controlling it is present, then theallele must be

a. mixed.

b. recessive.

c. hybrid.

d. dominant.


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Chapter11 Section01 Edit Oct 14th