GENETICSGENETICSCh. 11Ch. 11

Gregor MendelGregor Mendel Genetics is the study Genetics is the study

of of heredityheredity..

Gregor Mendel Gregor Mendel (1860’s)(1860’s) discovered discovered the fundamental the fundamental principles principles ofof geneticsgenetics by by breedingbreeding garden garden peaspeas..

2. Mendel 2. Mendel cross-cross-pollinated pollinated pea plantspea plants

He cut away He cut away the male the male parts of one parts of one flower, then flower, then dusted it with dusted it with pollen from pollen from anotheranother

3. What did Mendel 3. What did Mendel conclude?conclude?

He concluded that factors are passed He concluded that factors are passed from one generation to the next.from one generation to the next.

4. The Principle 4. The Principle of Dominanceof Dominance

AllelesAlleles

1.1. Alternative forms of Alternative forms of genes.genes.

2.2. Units that determine Units that determine heritable traits.heritable traits.

Paternal Maternal

eye color locusB = brown eyes

eye color locusb = blue eyes

The Principle of The Principle of DominanceDominance – some – some alleles are alleles are dominant and other dominant and other are recessive.are recessive.

5. Dominant and 5. Dominant and Recessive allelesRecessive alleles

Dominant alleles – upper-case Dominant alleles – upper-case a. homozygous dominanta. homozygous dominant

((BB BB – – Brown eyesBrown eyes))

Recessive alleles – lower caseRecessive alleles – lower casea. homozygous recessivea. homozygous recessive

((bb – blue eyesbb – blue eyes))b. Heterozygousb. Heterozygous ( (Bb – Brown Bb – Brown

eyeseyes))

Phenotype vs. GenotypePhenotype vs. Genotype

Outward appearanceOutward appearance Physical Physical

characteristicscharacteristics

Examples:Examples:

1.Brown eyes1.Brown eyes2.blue eyes2.blue eyes

Arrangement of Arrangement of genes that genes that produces the produces the phenotypephenotype

Example:Example:

1.1. TT, TtTT, Tt

2. 2. tttt

6. Segregation6. SegregationAlleles separate during meiosisAlleles separate during meiosis

7. Recessive traits show 7. Recessive traits show up about 1/4up about 1/4thth of the of the time.time.

Because there is Because there is only a 25% chance only a 25% chance that two recessive that two recessive alleles will be alleles will be paired together.paired together.

9. Punnett square9. Punnett square

A A Punnett square Punnett square is is used to show the used to show the possible possible combinationscombinations of of gametesgametes..

Monohybrid CrossMonohybrid Cross

Monohybrid CrossMonohybrid Cross

ExampleExample:: Cross between two Cross between two heterozygotesheterozygotes for for brown eyes (Bb)brown eyes (Bb)

BB = brown eyesBB = brown eyes

Bb = brown eyesBb = brown eyes

bb = blue eyesbb = blue eyesB

b

B b

Bb x Bb

malegametes

female gametes

Monohybrid CrossMonohybrid Cross

BB

Bb

Bb

bb

B

b

B b

Bb x Bb

1/4 = BB - brown eyed1/2 = Bb - brown eyed1/4 = bb - blue eyed

1:2:1 genotype 3:1 phenotype

Dihybrid CrossDihybrid Cross

Dihybrid CrossDihybrid Cross

RYRY RyRy rYrY ryry

RYRY

RyRy

rYrY

ryry

Dihybrid CrossDihybrid Cross

RRYY

RRYy

RrYY

RrYy

RRYy

RRyy

RrYy

Rryy

RrYY

RrYy

rrYY

rrYy

RrYy

Rryy

rrYy

rryy

Round/Yellow: 9

Round/green: 3

wrinkled/Yellow: 3

wrinkled/green: 1

9:3:3:1 phenotypic ratio

RYRY RyRy rYrY ryry

RYRY

RyRy

rYrY

ryry

Dihybrid CrossDihybrid Cross

Example:Example: cross between cross between roundround and and yellowyellow heterozygous pea seeds.heterozygous pea seeds.

RR = round= round

rr = wrinkled= wrinkled

YY = yellow= yellow

yy = green= greenRY Ry rY ry RY Ry rY ry x RY Ry rY ryRY Ry rY ry possible gametes produced

RrYyRrYy x RrYyRrYy

10. Independent Assortment10. Independent Assortment

Bb

diploid (2n)

B

b

meiosis I

B

B

b

b

sperm

haploid (n)

meiosis II

Chromosomes separate Chromosomes separate independently of independently of eachothereachother

Bb

Ff

B

F

B

f

b

f

B

F

Bb

Ff

Bb

Ff

This means all gametes will be different!

Independent AssortmentIndependent Assortment

Genes for different traits can segretate Genes for different traits can segretate independently during the formation of independently during the formation of gametes without influencing eachothergametes without influencing eachother

Question: Question: How many gametes will be produced How many gametes will be produced for the following allele arrangements?for the following allele arrangements?

Remember:Remember: 22n n (n = # of heterozygotes) (n = # of heterozygotes)

1.1. RrYyRrYy

2.2. AaBbCCDdAaBbCCDd

3.3. MmNnOoPPQQRrssTtQqMmNnOoPPQQRrssTtQq

Answer:Answer:

1. RrYy: 21. RrYy: 2nn = 2 = 222 = = 4 gametes4 gametes

RY Ry rY ryRY Ry rY ry

2. AaBbCCDd: 22. AaBbCCDd: 2nn = 2 = 233 = = 8 gametes8 gametes

ABCD ABCd AbCD AbCdABCD ABCd AbCD AbCd

aBCD aBCd abCD abCD aBCD aBCd abCD abCD

3. MmNnOoPPQQRrssTtQq: 23. MmNnOoPPQQRrssTtQq: 2nn = 2 = 266 = = 64 gametes64 gametes

11. Incomplete 11. Incomplete DominanceDominance

One allele is not One allele is not completely dominant completely dominant over anotherover another

Rr

Rr

Rr

Rr

r

r

R R

All Rr = pink(heterozygous pink)

produces theFF11 generation generation

11. Codominance11. Codominance

Both alleles are Both alleles are expressedexpressed

Example:Example: blood blood

1.1. type Atype A = I= IAAIIAA or Ior IAAii

2.2. type Btype B = I= IBBIIBB or Ior IBBii

3.3. type ABtype AB = I= IAAIIBB

4.4. type Otype O = ii= ii

Black cow + white cow = spotted cow

12. Which shows more 12. Which shows more genetic variation. (more genetic variation. (more combos?)combos?)

Male CC with female Male CC with female CcCc

Male cc with female Male cc with female CcCc

C

c

c c

C

c

C C

Genetic EngineeringGenetic Engineering

Gene Gene TherapTherapyy

Is cloning a Is cloning a possibility?possibility? Is it right to use Is it right to use

cloning to create an cloning to create an entirely new human entirely new human being?being?

Is it ethical to create Is it ethical to create an embryonic copy of an embryonic copy of John Doe to supply John Doe to supply cells to keep John cells to keep John alive? alive?

Does a multicellular Does a multicellular ball of tissue -- an ball of tissue -- an embryo -- have the embryo -- have the same rights and same rights and status as a human status as a human being? being?

How does Mendel’s How does Mendel’s principles apply to principles apply to organismsorganisms

The basic principals The basic principals can be applied to can be applied to humans as well as humans as well as any other living any other living organism.organism.

And now it’s time for….And now it’s time for….

Spongebob Spongebob Genetics!!!!!Genetics!!!!!