Week 12

Genetics IChapter 11 pages 189-201

Genetics IIChapter 11 pages 202-209

EXAM III RESULTS

Total Students = 39 Total Pass= 15 (38.5%)Total Fail= 24 (61.5%)

Class Average = 63Top Score = 94Low Score = 32

90-100 80-89 70-79 60-69 50-59 40-49 30-390

1

2

3

4

5

6

7

8

9

EXAM III GRADE DISTRIBUTION

Number of Students

A B C D F F F

2

5

8 8

6

7

3

TROUBLE SPOTS

Questions answered incorrectly:#2 (61.5% (24/39))

#3 (41% (16/39))

#9 (46% (18/39))#19 (67% (26/39))#26 (47% (23/39))#49 (69% (27/39))

#s 10 and 50 were well answered in general

#49 A. MEIOSIS B. Pairing of homologous chromosomes only occurs in meiosis crossing over

Pairing of x-somes

HOMEWORK

Chapter 12 ALL including Self-tests

EXAM III Extra Credit- DUE MAY 10th

Aneuploidy

Euploidy= Correct number of chromosomes in a species

Aneuploidy= A change in the number of chromosomes due to nondisjuction

CHANGES IN CHROMOSOME STRUCTURE

Changes in chromosome structures are mutationsX-somes can break due to radiation, organic

chemicals and virusesEnd of chromosomes break and can go back

together improperly which leads to chromosomal mutations:

DeletionsDuplicationsTranslocationsInversions

Deletions Duplications

Inversions Translocations

DNA exists as chromatin or as a chromosome

DNA- Deoxyribonucleic Acid

A POLYMER of NUCLEOTIDES

How do we know that certain complications will arise if genes are added or deleted to portions

of chromosomes?Through the Study of Genetics!

Genetics is the study of biologically inherited traits

Ex. How will the deletion of section ‘a’ affect disease?

Genomics is the study of all of the genes in an organism

Genetics and Genomics

‘Inherited traits are determined by the elements of heredity that are transmitted from parent to offspring in reproduction; these elements of heredity are called genes.’

DNA is the molecule of heredity

Gregor Mendel, 1822-1884

The Father of GeneticsDarwin 1809-1882

Austrian Monk

Developed ‘ParticulateTheory of Inheretance’By studying Pea Plantsin the 1860s

Combined Math andBiology!

Used statistics and lawsof probability to studybiology

Mendel studied garden pea plants to understand the units of heredity

WHY?

At the time, the ‘Blending Concept of Inheritance’ was widely accepted

Blending Concept of Inheritance= an offspring’s genetic makeup is intermediate to that of its parents

Ex. A cross between red and white flowers will only generate PINK flowers

Is this true?

NO!! Because…

Red, Pink andWhite flowersresult in the 2nd

Generation!

Diverse forms couldnot evolve if the blending theory wascorrect.

If we only had intermediate forms with little variation, how could all of the

diversity we see have evolved?• Confused both Mendel and Darwin

• Genes had not been discovered and would not be discovered until 1869 by Friedrich Miescher

• The molecular makeup of genes was discovered, but the function of genes was still not well understood.

• By 1900 it was understood that chromosome number is nearly constant in the cells of any species.

• Seemed likely that chromosomes were carriers of genes.

How did Mendel and others come to the conclusion that chromosomes were the

carriers of genes?

Through the study of phenotypes and crossings of pea plants with various traits

GENOTYPE

The genes present in a particular organism orcell

PHENOTYPE

The set of an organism’sobservable properties resultingfrom the interaction of the organismsgenotype with its environment

‘ATCCGCATTACG’

P = Parental GenerationF1= First GenerationF2= Second Generation

Mendel’s 7 Pea Plant Traits

1.

2.

3.

4.

5.

6.

7.

Garden Pea Plant

Pisum sativum

Mendel’s Particulate Theory of Inheritance

• Mendel used the scientific method to understand inheritance in pea plants

• He created ‘pure’ or ‘true-breeding’ lines of plants for specific traits (ex. Round or smooth seeds, purple or white flowers…)

• He observed and tracked these phenotypes through multiple generations of pea plants

• Based on his studies, he determined that hereditary information is passed from parents to offspring in the form of discrete “particles” (which we now refer to as GENES)

Why study the Garden Pea Plant?

• Easy to cultivate• Short generation time• Can self pollinate - Able to create ‘true-breeders’• Can cross pollinate by hand• Traits easy to observe• Can observe dominant or recessive characteristics

‘True-Breeding’

- Anther contain Sperm

- Ovules in ovary contain Eggs

- Pea plants are able to ‘self- pollinate’

- Therefore, offspring are identicalto the parents

- Mendel bred plants ‘true’ to ensure the purity of each trait

Why secure the purity of each trait?

• Had to ensure that the trait he was observing was not confounded by other discrete particles

• Ex. He had to make sure that a white colored flower was truly white before making any crosses

• His experiments would have failed because he would have observed different outcomes each generation

Cross-Pollination

onto the stigmaof plant B

From plant AAfter self pollinatingplants for several generations to obtain‘true-breeding’ plantsMendel used the anther from one true-bred plant to pollinate the Stigmaof another true-bredplant= Cross Pollination

Mendel’s HypothesisHypothesis

Hereditary information is passed from parents to offspring in the form of discrete “particles”

Mendel’s Observations (3:1, D:R)

Mendel’s Laws

Based on his observations of cross-pollination studies:

1 LAW OF SEGREGATION

2 LAW OF INDEPENDENT ASSORTMENT

LAW OF SEGREGATION

Based on the hypothesis that if the blending theory of inheritance were true, then a cross should yield an “intermediate” phenotype in comparison to the parents

Ex. Tall plant x Short plant = Medium plant

Mendel tested this by crossing plant varieties that differed by only 1 single trait…

LAW OF SEGREGATIONMendel performed ‘reciprocal’ crosses:Dusted pollen of Tall plants onto Short plantsDusted pollen of short plants onto Tall plants

All F1 resembled the TALL parent! NOT intermediate!

Mendel allowed the F1s to self-pollinate ¾ of the F2 plants were Tall and ¼ of the F2 plants were short!

ALL F1s were TallNo intermediates observed!

ALL F1s would have hadthe same genetic makeupbecause the parents were bred true.

ALL of the F1 generation plants would have had a Tt genotype

One T from parent 1 (bred true for TALL) and one t from parent 2 (bred true for SHORT)

What happens when you cross two F1 generation plants?

X

Gametes

A true-bred TALL plant gametes will only be T

A true-bred SHORT plant gametes will only be t

Gametes

THEREFORE, the ONLY resulting GENOTYPE for the F1 generation is T t

F1 CROSS

X

What will the GENOTYPES of the GAMETES look like for this MONOHYBRID CROSS?

The F1s are allTt, therefore whenCross with each otherIt is a ‘mono’(one type) ‘hybrid’ (Tt) cross

What will the GENOTYPES of the GAMETES look like for this F1 MONOHYBRID

CROSS?

T t T t

F1 F1

T

tT t

T

t

T tF1 GAMETES

F2 GENOTYPESand PHENOTYPES

WHAT IS THE PHENOTYPIC RATIO OF TALL TO SHORT?

WHAT IS THE GENOTYPIC RATIO OF TALL TO SHORT?

3:1 TALL: SHORT Dominant:Recessive

Monohybrid crosses ALWAYS result in a 3:1 ratio

The SHORT trait is masked by the TALL trait in the F1 generation and is observed in the F2 generation

TALL is a dominant trait and SHORT is a recessive trait

LAW OF SEGREGATION

1 Each individual has two factors for each trait2 The factors ‘segregate’ during the formation

of gametes3 Each gamete contains only one factor from

each pair of factors4 Fertilization gives each new individual two

factors for each trait (haploiddiploid)

PAGE 192

Dominance

‘Tallness’ in pea plants is dominant to ‘shortness’Tall = TShort= t

If parent 1 = TT (tall plant) and parent 2 = tt (short plant)

ALL F1 generation plants will be Tt

Dominance

Genes occur at a particular ‘locus’ on a chromosome

Alternative versions of the same gene are called ‘alleles’

The dominant allele masks the expression of the recessive allele

A gene occurs at a particular locus

Alleles= Alternative versions of the same gene

MOM

DAD

If purple is dominant to white, the purple phenotype is observed, but you are a carrier for white!

Remember: only 1 allele of each trait is in a gamete (meiosis!)

GENOTYPES

TT = Homozygous dominant (Tall Plant)Tt = Heterozygous (Tall Plant) tt = Homozygous recessive (Short Plant)

Phenotypes

PUNNETT SQUARES

• Used to predict breeding outcomes• Able to calculate probability of traits

Example:T tt t

T tt t

MENDEL’S LAW OF INDEPENDENT ASSORTMENT

Mendel experimented with plants that differed in 2 traits

The plants are hybrid in 2 ways therefore the crosses between the F1 generation are ‘DIHYBRID CROSSES’

2 traitsTallGreen pods

2 traitsshortYellow pods

DiHybrid Cross Cont.’d

X

Sperm Eggs

?F1 GAMETES ?

DiHybrid Cross Cont.’d

X

Sperm Eggs

F1 GAMETES

TG

Tg

tG

tg

TG

Tg

tG

tg

Mendel’s Dihybrid Cross Hypothesis I

If the dominant factors always segregate together (=TG) and the recessive factors segregate together (=tg), then there would be two phenotypes among the F2 plants ONLY, tall plants (T) with green pods(G) and short plants (t) with yellow pods (g)

Did Mendel observe this to be true? NO!!!

Mendel’s Dihybrid Cross Hypothesis II

If the four factors (T, G, t, g) segregate into the F1 gametes independently, then there would be four phenotypes among the F2 plants

Tall and green podsTall and yellow podsShort and green podsShort and yellow pods

Did Mendel observe this to be true? YES!!!!!

Mendel’s Dihybrid Cross Observations 9:3:3:1

9:3:3:1Dihybrid crosses always have this phenotypic ratio!!!

LAW OF INDEPENDENT ASSORTMENT

1 Each pair of ‘factors’ segregates (assorts) independently of the other pairs

2 All possible combinations of factors can occur in the gametes

PAGE 194

Mendel and Meiosis

Homologous pairs of chromosomes line up randomly at the metaphase plate

This allows for independent segregation during gamete formation

Probability

Wouldn’t it be nice to know the outcome of a particular cross?

- Punnett squares enable us to calculate the chance or probability of genotypes and phenotypes of offspring

- How likely is it that an offspring will inherit a specific set of two alleles, one from each parent?

The Product Rule of Probability

What is the chance of offspring having:

EE

Ee

eE

ee

1/2 1/2

1/2 1/2

1/2 1/2

1/2 1/2

x

x

x

x

=

=

=

=

1/4

1/4

1/4

1/4

The Product Rule of Probability

In a monohybrid cross, we know that eachChild has a 25% (1/4) chance of having attached Earlobes

The SUM Rule tells us that we can add togetherall of the same phenotypic traits:Ex. ¾ or 75% of the children will have unattachedEarlobes (¼ + ¼ + ¼ = 3/4)

Ratios

MONOHYBRID Crosses ALWAYS result in a:3:1 ratio

3 Dominant: 1 Recessive trait(Rr x Rr)

DIHYBRID Crosses ALWAYS result in a:9:3:3:1 ratio

9 Dominant: 3 Dominant and Recessive: 3 Dominant and Recessive :1 Recessive

(TtGg x TtGg)

YOUR TURN!

In Pea Plants, yellow seed color (Y) is dominant over green seed color (y).

When two heterozygous plants are crossed, what percentage of plants would have yellow seeds?

What percentage would have green seeds?¾ or 75%

¼ or 25%

YOUR TURN!

In humans, pointed eyebrows (B) are dominant over smooth eyebrows (b). Mary’s father has pointed eyebrows, but she and her mother have smooth eyebrows. What is the genotype of the father?

Mary’s father can’t have a BB genotype otherwise all of the offspring would have pointed eyebrows. He can’t be bb otherwise he would havesmooth eyebrows. He MUST have a Bb genotype in order for Maryto have smooth eyebrows.

Testcrosses

Testcrosses are performed in order to figure out the genotype underlying a particular phenotype

Mendel performed test crosses of F1 individuals with “true-bred” individuals to figure out the laws of segregation (that alleles segregate independently during gamete formation)

Testcrosses

One-trait test cross:

Individual w/ Dominant phenotype is heterozygous

Individual w/ Dominant phenotype is homozygous

Testcrosses

Two trait test-crosses:Individual w/ dominant phenotype is crossed

with one having the recessive phenotype

Is the fly on the left heterozygous or homozygous for wing and body color?

WE HAVE NO IDEA SO WE MUST TESTCROSS TO DETERMINE THE GENOTYPE!!

For fruit flies (Drosophila melanogaster) we know:

L = long wings G=gray bodiesl = short (vestigial) wings g =black bodies

What are the genotypes for these flies?

The black fly with short wings MUST be llgg

If these are the offspring between the homozygous recessive (black/short wings) and the gray body with long wings, what was the gray/long fly’s

genotype? llgg x ? =

For fruit flies (Drosophila melanogaster) we know:

L = long wings G=gray bodiesl = short (vestigial) wings g =black bodies

What is the genotype for the gray/long fly?

llggIf Dominant for both traits=

If Heterozygous for both traits =

LLGG

LlGg

If Dominant Homozygous:

llggLLGG xGametes

LGLGLGLG

Gametes

lglglglg

Punnett Square

lg lg lg lg

LG

LG

LG

LG

LlGg

LlGg

LlGg

LlGg LlGg

LlGg

LlGg

LlGg LlGg

LlGg

LlGg

LlGg LlGg

LlGg

LlGg

LlGg

X

ALL of the flies would have the same phenotype if the gray/long fly had a LG genotype!!

We know these are the offspring and they are not all gray with long

wings!!! So…..

If Dominant Homozygous:

llggLlGg xGametes

LGLglGlg

Gametes

lglglglg

Punnett Square

lg lg lg lgX

LG

Lg

lG

lg

LlGg LlGg LlGg LlGg

Llgg Llgg Llgg Llgg

llGg llGg llGg llGg

llgg llgg llgg llgg

25%=Long/Gray

25%=Long/Black

25%=Short/Gray

25%=Short/Black

25%= LlGg, 25%= Llgg, 25%= llGg, 25%= llgg

MUST be heterozygous for both traits!!

This is the only way a homozygous recessivefly could have been produced!

When crossing a heterozygous for two trait Individual w/ an individual recessive for both Traits the ratio is always:

1:1:1:1

Mendel’s Laws and Human Genetic Disorders

Two types of human genetic disorders:

1 Autosomal (x-somes other than X or Y)– Recessive– Dominant

2 X-linked (x-somes that are X or Y)

Autosomal Patterns of Inheritance

Autosomal DominantIndividual with AA or Aa HAS the disordera = recessive

Autosomal RecessiveInvididual with aa HAS the disorderA= dominant

Pedigrees

Pedigrees are used to track patterns of inheritance of a particular condition and to determine dominance or recessiveness

For Example:

= MALE

= FEMALE

= A UNION

= A CHILD

Pedigrees

-The shaded/colored shapes do not indicate whether the person is dominant or recessive

-Only indicates that the person is affected

PedigreesIn these pedigrees, which is autosomal

dominant and which is autosomal recessive?

= MALE

= FEMALE

I Only the Child is affected II Only the Parents are affected

Autosomal RECESSIVE Most affected children have unaffected parents Heterozygotes (Aa)have an unaffected phenotype Two affected parents will always have affected children Close relatives who reproduce are more likely to have affected

children Both males and females are affected with equal frequency

Aa Aa

aa Autosomal recessiveHAS disorder

Autosomal DOMINANT Affected children will usually have an unaffected parent Heterozygotes (Aa) ARE affected Two affected parents can produce an unaffected child Two unaffected parents will not have affected children Both males and females are affected with equal frequency

Aa Aa

aa

Carriers

In Pattern I, the parents are Carriers for the condition, but they do not exhibit the condition themselves

Is this pattern Autosomal Dominant or Recessive?

RECESSIVE!

*The double line indicates inbreeding/breedingBetween closely related individuals(Inbreeding increased frequency of obtaining the disorder

Is this pattern Autosomal Dominant or Recessive?

DOMINANT!

Note that BOTH heterozygotes HAVE thecondition

Autosomal Recessive Disorders

1 Methemoglobinemia

2 Cystic Fibrosis

3 Nieman-Pick Disease

Methemoglobinemia

An accumulation of methemoglobin in the blood causing the blood to appear blue instead of red skin appears blue in color

Hemoglobin Methemoglobin

Those affected lack enzyme diaphorase that converts Methemoglobin back to hemoglobin (enzyme is coded for in gene on x-some 22)Autosomal RECESSIVE trait

Cystic Fibrosis (CF)

• Most common lethal genetic disease among Caucasians in the US (1/20=carrier, 1/2000 newborns has the disease)

• Caused by a defective chloride ion channel (protein channel) located in the cell membrane

• Cl- ions fail to pass through the channel which in turn does not allow Na+ or water to pass

• Lack of water leads to thick mucus in the bronchial tubes and pancreatic ducts

Cystic Fibrosis (CF)Life expectancy is usually into the teens and twenties,

but some people can live as many as 35 years with the disease

Gene therapy is currently being researched to correct the defective gene that produces the faulty protein

CFTR= Cystic FibrosisTransmembrane ConductanceRegulator

The CFTR geneis located on Chromosome 7

Studied Cystic Fibrosis by researching the effect of various toxins on the regulation of Chloride secretion in dogfish shark rectal glands in Mount Desert Island Biological Laboratories in Mount Desert Island, Maine

Performed dogfish shark rectal gland perfusions

Summers of 1998 and 1999

Squalus acanthias

Nieman-Pick Disease

Caused by defective versions of the same gene located on chromosome 11

Normally, Gene codes for enzyme, sphingomyelinase which breaks down sphingomyelin (a lipid)

Without proper functioning enzyme, lipid droplets accumulate in the cells of the liver, lymph nodes and spleen

Type A= lipid droplet buildup in brain neurological disorders Type B= milder form, protein has some function Children present with persistant jaundice, feeding difficulties,

enlarged abdomen, pronounced mental retardation

Autosomal Dominant Disorders

1 Osteogenesis Imperfecta

2 Hereditary Spherocytosis

Osteogenesis Imperfecta

• Autosomal dominant disorder• Caused by mutations in 2 genes needed to

synthesize type I collagen• Defective collagen I is produced• Results in weak, brittle bones• Defective collagen can combine with

normal collagen and can cause structural defects• Incidence=1/5,000 live births• Treated with drugs

Hereditary Spherocytosis• Autosomal dominant genetic blood disorder• Caused by defective copy of ankyrin-1 gene found on

x-some 8• Leads to defective protein normally responsible for

the structure and shape maintenance of red blood cells (RBCs)

• RBCs become spherical and burst easily due to osmotic stress

• Incidence = 1/5,000• Some cases (25%) are spontaneous mutations and

are not inherited by either parent

Mendel’s Laws and Human Genetic Disorders

Two types of human genetic disorders:

1 Autosomal (x-somes other than X or Y)– Recessive– Dominant

2 X-linked (x-somes that are X or Y)

X-Linked Inheritance • Refers to genes that are carried on the X chromosome• Chromosome theory of inheritance (Thomas Hunt Morgan,

1900s)- specific alleles correspond specifically with the X chromosome

• The Y chromosome lacks these alleles• Males always receive an X-linked recessive mutant allele from

the female parent, therefore sex linked recessive traits appear more frequently in males

• Males can not be carriers for X-linked traits• Males express whatever allele is present on the x-

chromosome and are therefore ‘hemizygous’ for X-linked traits

Morgan’s Observations

Used fruit flies (Drosophila melanogaster) b/c they have the same chromosome pattern as humans.

White eyes onlyObserved in Males!

Males can onlyInherit the recessiveAllele from the Female parent

Note: the allele is nowassociated with theX chromosome

The F1s will all have red eyes because the female is XR homozygous dominant!

What will the F1 gametes look like?

XR XRY Xr

The F1 Cross

Result of F1 crossis that only 1male has white eyes

Females will only havewhite eyes when theyreceive a recessiveallele from both parents

Human X-linked Recessive Disorders

1 Color Blindness

2 Hemophilia

3 Muscular Dystrophy

4 Adrenoleukodystrophy

5 Menkes Syndrome

Color Blindness• 3 classes of cone cells in the retina of the

human eye and each contains either:1. Blue-sensitive pigment proteins2. Red-sensitive pigment proteins3. Green-sensitive pigment proteins

Red and green sensitive pigment proteins are on the X-chromosome

Blue-sensitive pigment proteins are autosomalUsuallly passes from grandfather to grandson

through a carrier daughter

X-linked Recessive Pedigree

8% of Caucasian males havered-green colorblindnessBright Green= tanOlive green= brownReds= reddish brownSome only see yellow, blue, blackwhite and gray

Hemophilia

1/10,000 males is a hemophiliac

Two types:Hemophilia A- due to absence/minimal

presence of clotting factor VIIIHemophilia B- due to absence of clotting factor

IXHemophiliacs lack the ability to clot blood or

they clot blood very slowly

Hemophilia: a Royal Pain

Queen VictoriaQueen of England (and Ireland)b.1819- d.19019 children

Hemophilia “A Royal Disease”

Other Types of Inheritance

1 Multiple Allelic Traits

2 Incomplete Dominance and Incomplete Penetrance

3 Pleiotropic Effects

4 Polygenic Inheritance

Multiple Allelic Traits

When traits are controlled by multiple alleles, the gene exists in several allelic forms

Ex. Human blood types are A B OThere are 3 possible alleles that determine the

blood type BUT….

The A B O blood type is controlled by a single gene pair

Alleles determine the presence or absence of antigens on red blood cells

IA = A antigen on red blood cellsIB = B antigen on red blood cellsi = Neither A nor B antigen on red blood cells

Possible phenotypes or genotypes:Phenotype GenotypeA IAIA, IAiB IBIB, IBiAB IAIB

O ii

CODOMINANCEInheritance of blood types in humans is an

example of Codominance

Both IA and IB are fully expressed in the presence of the other

A person who is IAIB will have blood type ABIA is not dominant over IB

IB is not dominant over IA

IA and IB are dominant over ii

AOAAAOAA

BOBB

AB

OO

Universal Recipient

Universal Donor

Incomplete Dominance and Incomplete Penetrance

Incomplete Dominance:When the heterozygote (Aa) exhibits an

intermediate phenotype

Incomplete Penetrance:When the dominant allele in a heterozygote

does not lead to the dominant phenotypeThe dominant allele may not always determine

the phenotype

Incomplete Dominance

R1 = allele for red pigmentR2 = allele for no pigment

Incomplete Penetrance

Ex. Polydactyly (extra digits onhands, feet or both)

Is inherited as autosomal dominantBUT, not all individuals exhibit the trait who Inherit the dominant allele

Other genes may influence the appearance of the trait

Pleiotropic EffectsOccurs when a single mutant gene affects two or more

distinct, unrelated traitsEx. Sickle-cell diseaseResults from a mutation in gene coding for hemoglobin

polypeptideMutation causes change in 1 amino acid in the

hemoglobin polypeptideCauses RBCs to be sickle-shaped

-Slows blood flow -Decreased O2 carrying

-Clogs blood vessels

-Cells have shorter life span

capacity-Resistant to Malaria!

-Severe Anemia

Polygenic InheritanceThe expression of a trait is controlled by two or more sets of

alleles at different loci on different chromosomes =polygenes (each allele contributes to the phenotype)

Dominant alleles have a quantitative effect on the phenotype= they are additive

This leads to ‘multifactorial traits’continuous variation in phenotypes and genotypes

Ex. To what degree does a gene contribute to a trait? How much is due to Environment?

The study of this kind of inheritance= Quantitative Genetics(estimates of heritability- I did this by breeding fish!!)

Doiminant pairs of genes

Multiple outcomes due to several pairs ofgenes controlling a trait

Orange shading represents environmentalinfluence

WHAT KIND OF HUMAN TRAITS EXHIBITPOLYGENIC/MULTIFACTORIAL INHERITANCE?

Individual genes of a polygenic trait follow Mendel's laws, but together do not produce Mendelian ratios =bell shaped curve

WHAT KIND OF HUMAN TRAITS EXHIBITPOLYGENIC/MULTIFACTORIAL

INHERITANCE?QUANTITATIVE TRAITS:• Skin color (allele frequencies are the best indicator of shared

heritage in a population, therefore, skin color alone does not effectively indicate a person's ethnic and genetic background, sun exposure is an environmental factor)

• Height (varies continuously in a bell shape distribution, Diet and health are environmental factors)

• Hair color (little environmental influence)• Body Mass (Diet and health are environmental factors)• Finger print patterns (environmental influence possible

during gestation)• Eye color (little environmental influence, five human eye

colors, interact additively)

HAIR COLOR– Hair color is controlled by alleles on chromosomes

3, 6, 10, and 18. – The more dominant alleles that appear in the

genotype, the darker the hair.

Pepper Color

Gene 1: R= red r= yellow

Gene 2: Y= absence of chlorophyll (no green) y= presence of chlorophyll (green)

Pepper Color

Genotypes: Phenotypes:

R-/Y- : (red/no chlorophyll)R-/yy : (red/chlorophyll)rr/Y- : (yellow/no chlorophyll)rr/yy : (yellow/chlorophyll)

“-” Indicates that genotype could be hetero or homozygous

RedBrown/orangeYellowGreen

Pepper Color

• Try crossing a brown pepper (RRyy) with a yellow pepper (rrYY).

• Which trait will your offspring (F1 generation) produce?

• What traits are produced when you cross two of the peppers found in the F1 generation?

THIS WEEK IN YOUR LAB

DNA Fingerprinting:

Restriction Fragment LengthPolymorphisms (RFLPs)

Individual 1 2 3 4 5 6 7 8 9 10