Block Day- April 25, 2012Homework: none

Make an entry- Entry 41:Heredity and Genetics2- 4/25/12 See attached entry

Symbols used for alleles• The traditional symbols used for alleles

are big and small letters• The letter chosen usually refers to the

dominant alleleExample: R = Red allele

r = Blue allele

The combination of alleles determines the observed characteristics

REDalleleChromosome

combination

Allelecombination

Observedcharacteristic

RED allele

REDallele

BLUE allele

BLUEallele

BLUE allele

red, red red, blue(or blue, red)

blue, blue

RED RED BLUE

The combination of alleles determines the observed characteristics

RChromosomecombination

Allelecombination

Observedcharacteristic

RR Rr rr

RED RED BLUE

R R r r r

The combination of alleles determines the observed characteristics

RChromosomecombination

GENOTYPE

PHENOTYPE

RR Rr rr

RED RED BLUE

R R r r r

Homozygous – the two alleles are the same

• RR and rr are homozygous genotypes

Heterozygous – the two alleles are different

• Rr is a heterozygous genotype

Draw the enzymes and pigment molecules present in the cells of each type of flower below.

GENOTYPE for flower type 2:

Allele of chromosome 2A= Y1 (functional enzyme)

PHENOTYPEof flower type 2:

nucleus

Y1

Y2

Yes or no, is any functional enzyme Y in the cell?

Allele of chromosome 2B= Y2 (non-functional enzyme) 2A 2B

1B

1A

YES RED

WHAT DOES Rr ACTUALLY MEAN?

Rr

Possible combinations of inherited chromosomes/genes

R rR r

Dad Mom

R

r

Parents

PossibleOffspring r

r

R

R

r

R

X

Order doesn’t matter, these two are the same (Rr)

What are all possible genotypes produced from the parents?

RR, Rr, rr

Punnett squares organize all possible offspring combinations

R r R rX

R r

R

r

RR

Rr rr

Rr

Dad Mom

1 out of 4 possibilities is rr = What is probability of Rr?• How many out of 4 are red? • What is the probability of red? • What is the probability of blue?

R r

R RR Rr

r Rr rrGenotypic ratio = 1RR: 2Rr:1rr

25 %50 %

3/475 %25 %

R= red flower alleler= blue flower allele

Phenotypic ratio = 3 Red:1 blue

Your turn:• What are all possible genotypes and

phenotypes produced by crossing Rr with rr?

Complete the Punnett Square

r r

R Rr Rr

r rr rr

Punnett squares predict ratios of all genotypes and phenotypes produced

Genotypic ratio = 2 Rr:2 rr or 1Rr : 1 rrPhenotypic ratio = 2 Red:2 Blue or 1 Red : 1 Blue

r r

R Rr Rr

r rr rr

R= red flower alleler= blue flower allele

Punnett square practiceCalculate the predicted genotypic and phenotypic ratios1) Hh X HH H(hairy) is dominant over h(not hairy)

2a) Gg X gg G(green sepals) is dominant over g(yellow sepals)2b) What would the cells of the green and yellow

plants look like? (functional vs non-functional)

Genotypic ratio = 2 HH:2 Hh or 1HH : 1HhPhenotypic ratio = 4 Hairy: 0 Non-hairy

H H

H HH HH

h Hh Hh

Genotypic ratio = 2 Gg:2 gg or 1Gg : 1ggPhenotypic ratio = 2 Green: 2 Yellow or 1 Green : 1 Yellow

g g

G Gg Gg

g gg gg

GENOTYPE for Green Flower (Gg) :

Allele of chromosome A= C1 (functional enzyme)

PHENOTYPEof flower type 2:

nucleus

Yes or no, is any functional enzyme C in the cell?

Allele of chromosome B= C2 (non-functional enzyme)

Y1

Y2

A

B

1B1A

GENOTYPE for yellow flower (gg):

Allele of chromosome A= C2 (non-functional enzyme)

PHENOTYPEof flower type 3:

nucleus

Y2

Y2

Yes or no, is any functional enzyme Y in the cell?

Allele of chromosome B= C2 (non-functional enzyme)

A

B1B

1A

YES

Green

NO

Yellow

Make an entry- Entry 42: Punnett Square Worksheet- 4/25/12

See attached entry

• #1 In rabbits, black fur is dominant over white fur. Show the cross of a heterozygous black male with a homozygous white female.

• Parents: Bb x bb b b • Genotypic Ratio: B  1 Bb : 1bb • Phenotypic Ratio: b 1 black: 1 white

Bb Bb

bb bb

• #2 Tall is dominant over short in pea plants. Show the cross of a homozygous short plant is crossed with a homozygous tall plant.

• Parents: tt x TT  • Genotypic Ratio:   4 Tt (or 100% Tt) • Phenotypic Ratio: All or 100% Tall

Tt Tt

Tt Tt

T T

t

t

• # 3 In humans, free-ear lobes are dominant to attached ear lobes. Two parents that are both heterozygous free are expecting a child. What are the chances that the child will have free ear lobes of attached?

• Parents: Ff x Ff   F f • Genotypic Ratio: F  1 FF:2Ff: 1ff • Phenotypic Ratio: f 3 Free: 1 attached

FF Ff

Ff ff

#4

S=smooths= wrinkledParents: ss x SsGenotypic ratio: 2 Ss:2 ssPhenotypic ratio: 2 smooth: 2 wrinkled

#5

S=smooths= wrinkledParents: Ss x SsGenotypic ratio: 1 SS: 2Ss: 1ssPhenotypic ratio: 3 smooth: 1 wrinkled

#6

B=blue eyesb=red eyesParents: Bb x bbGenotypic ratio: 2 Bb: 2 bbPhenotypic ratio: 2 blue eyes: 2 red eyes

#7

R= red eyesr= white eyesParents: rr x rrGenotypic Ratio: 4 rr or all rrPhenotypic: 4 white eyes or all white eyes

• #8 A homozygous dominant brown mouse is crossed with a heterozygous brown mouse (tan is the recessive color).

• Parents: BB x Bb B b • Genotypic Ratio: B  1 BB : 1Bb • Phenotypic Ratio: B All Brown or 4 Brown: 0 Tan

BB Bb

BB Bb

• #9 Two heterozygous white (brown fur is recessive) rabbits are crossed.

• Parents: Ww x Ww Genotypic Ratio: 1WW:2Ww:1ww • Phenotypic Ratio: 3 WHITE: 1 BROWN W w

W

w

WW Ww

Ww ww