Mendel & His Plants!Mendel & His Plants!

Gregor Mendel bred Gregor Mendel bred pea plants and pea plants and recorded inheritance recorded inheritance patterns in the patterns in the offspring. offspring.

Mendel’s ExperimentMendel’s Experiment

Mendel bred true-breeding plantsMendel bred true-breeding plants

When self-fertilized, a When self-fertilized, a true-breedingtrue-breeding plant plant produces offspring identical in appearance produces offspring identical in appearance to itself generation after generation. to itself generation after generation.

Mendel’s ExperimentMendel’s Experiment

Mendel crossed 2 Mendel crossed 2 plants- 1 true-breeding plants- 1 true-breeding for purple and 1 true-for purple and 1 true-breeding for white (P breeding for white (P generation)generation)

He got the following He got the following results: (F1 results: (F1 generation)generation)

How did he cross the plants?How did he cross the plants?

Step 2: Crossing the F1 generationStep 2: Crossing the F1 generation

One trait is One trait is dominant dominant

One trait is One trait is recessiverecessive

Ratio of Dominant : Ratio of Dominant : recessiverecessive

12 purple: 4 white = 12 purple: 4 white = 3 purple: 1 white3 purple: 1 white

Section 11-1

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Parents (P)

Long stems short stems

Red flowers white flowers

Green pods yellow pods

Round seeds wrinkled seeds

Yellow seeds green seeds

First Generation (F1)

All long

All red

All green

All round

All yellow

Second Generation (F2)

787 long: 277 short

705 red: 224 white

428 green: 152 yellow

5474 round: 1850 wrinkled

6022 yellow: 2001 green

Mendel’s ResultsMendel’s Results

1. In the first generation of each 1. In the first generation of each experiment, how do the characteristics of experiment, how do the characteristics of the offspring compare to the parents’ the offspring compare to the parents’ characteristics?characteristics?

2. How do the characteristics of the 2. How do the characteristics of the second generation compare to the second generation compare to the characteristics of the first generation?characteristics of the first generation?

Using Diagrams to show Using Diagrams to show inheritance: Punnett Squaresinheritance: Punnett Squares

P P pp

P p P p

pP P p

Alleles= Alleles= alternativalternative forms of e forms of genesgenes

P = P = purplepurple

p= whitep= white

A B C D F

1

2

3

4

5

Rules for Punnett SquaresRules for Punnett Squares

1. Draw a square1. Draw a square Place the traits for each parent across the top Place the traits for each parent across the top

and side (alleles)and side (alleles) Bring down the alleles from the top and across Bring down the alleles from the top and across

from the sidefrom the side Write the final ratio for the genotype & Write the final ratio for the genotype &

phenotypephenotype Add proper vocab terms Add proper vocab terms

(homozygous/heterozygous AND Dom & (homozygous/heterozygous AND Dom & Recessive)Recessive)

Perform the following cross from the F1 Perform the following cross from the F1 generation using a Punnett Squaregeneration using a Punnett Square

Try Another!Try Another!

Inheritance & ProbabilityInheritance & Probability

We have been examining inheritance using We have been examining inheritance using probabliltyprobablilty

Probabilities predict AVERAGES! Not Probabilities predict AVERAGES! Not individuals.individuals.

The offspring may not exactly match the The offspring may not exactly match the predicted outcome (the larger the sample, the predicted outcome (the larger the sample, the closer the expected values)closer the expected values)

25% WW (homozygous dominant)25% WW (homozygous dominant) 25% ww (homozygous recessive)25% ww (homozygous recessive) 50% Ww (heterozygous)50% Ww (heterozygous)

75% White75% White 25% Black25% Black

Will it always turn out this way???Will it always turn out this way???

Two Factor/ Two Trait CrossesTwo Factor/ Two Trait Crosses

Law of SegregationLaw of SegregationAlleles separate from one another during Alleles separate from one another during

meiosismeiosisLaw of Independent AssortmentLaw of Independent Assortment

Alleles segregate independently of one Alleles segregate independently of one another (one does not depend on the other)another (one does not depend on the other)

Two Trait CrossesTwo Trait CrossesSeparate the alleles using the FOIL Separate the alleles using the FOIL

method (kind of like a method (kind of like a ))

R r Y yR r Y y

RrYy x RrYyRrYy x RrYyRY Ry rY ry

RY Ry rY ry

RY Ry rY ryRrYy xRrYy x

RrYyRrYy

Two Trait CrossesTwo Trait Crosses

Genotypic Ratio:Genotypic Ratio:

1/16 RRYY1/16 RRYY

1/8 RRYy1/8 RRYy

1/16 RRyy1/16 RRyy

1/8 RrYY1/8 RrYY

¼ RrYy¼ RrYy

1/8 Rryy

1/8 rrYy

1/16 rrYY

1/16 rryy

Phenotypic RatioPhenotypic Ratio

9 Yellow Round9 Yellow Round3 Yellow wrinkled3 Yellow wrinkled3 green round3 green round1 green wrinkled1 green wrinkled

ALL Heterozygote two-trait crosses will ALL Heterozygote two-trait crosses will result in a 9:3:3:1 ratioresult in a 9:3:3:1 ratio

Phenotypic Ratio for 2 trait crossesPhenotypic Ratio for 2 trait crosses

9 dominant dominant9 dominant dominant3 dominant recessive3 dominant recessive3 recessive dominant3 recessive dominant1 recessive recessive1 recessive recessive

A Few Different Types of A Few Different Types of InheritanceInheritance

http://www2.edc.org/weblabs/incompletedom/incompletedominancemenu.html

A New Kind of InheritanceA New Kind of Inheritance

Heterozygous Heterozygous phenotype is a phenotype is a blending of the blending of the recessive and recessive and dominant traits.dominant traits.

What kind of What kind of inheritance?inheritance?

Incomplete Dom.Incomplete Dom.

CodominanceCodominance

The dominant AND The dominant AND the recessive are both the recessive are both expressedexpressed

RR x rrRR x rr

Multiple AllelesMultiple Alleles

Genes with more than two alleles. Genes with more than two alleles. Ex: RabbitsEx: Rabbits

C = full color; dominant to all other allelesC = full color; dominant to all other alleles CCchch = chinchilla, partial defect in = chinchilla, partial defect in

pigmentation, dominant to pigmentation, dominant to cchh and and cc alleles alleles cchh Himilayan, color on certain parts of the Himilayan, color on certain parts of the

bodybody c= albino, no colorc= albino, no color

Cc?

cc?

cchch?

chc?

Codominant CrossCodominant Cross

Predict the genotypic and phenotypic ratio Predict the genotypic and phenotypic ratio of a cross between a Full Color Rabbit of a cross between a Full Color Rabbit (C(Ccchh) ) and a himilayan ( and a himilayan (cchhc).c).

Genotype: 25% Genotype: 25% CCcchh, 25%, 25%CCc, 25% cc, 25% chhcchh, c, chhccPhenotype: 50% Full color, 50% himilayanPhenotype: 50% Full color, 50% himilayan

Sex-Linked GenesSex-Linked Genes

Even the X and Y chromosomes code for traitsEven the X and Y chromosomes code for traits Since males only have one X chromosome, all traits are Since males only have one X chromosome, all traits are

expressed… even the recessive!expressed… even the recessive! This explains why males are much more likely to developThis explains why males are much more likely to develop

ColorblindnessColorblindness HemophiliaHemophilia Duchenne Muscular Dystrophy Duchenne Muscular Dystrophy

These are all genes on the XThese are all genes on the X

chromosome!chromosome!

Sex Linked CrossSex Linked Cross

XXHH

XXhh

XXHH

YY

XXHH XXHH

XXHH XXhh

XXHH YY

XXhhYY

X-InactivationX-Inactivation

How many X chromosomes do females How many X chromosomes do females have?have?

How many X chromosomes do males How many X chromosomes do males have?have?

Why do females need 2?Why do females need 2?