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GENETICS Ch. 11. Gregor Mendel. Genetics is the study of heredity . Gregor Mendel (1860’s) discovered the fundamental principles of genetics by breeding garden peas . 2. Mendel cross-pollinated pea plants.

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gregor mendel
Gregor Mendel
  • Genetics is the study of heredity.
  • Gregor Mendel (1860’s) discovered the fundamental principles of genetics by breedinggarden peas.
2 mendel cross pollinated pea plants
2. Mendel cross-pollinated pea plants
  • He cut away the male parts of one flower, then dusted it with pollen from another
3 what did mendel conclude
3. What did Mendel conclude?
  • He concluded that factors are passed from one generation to the next.
4 the principle of dominance

eye color locus

B = brown eyes

eye color locus

b = blue eyes

Paternal

Maternal

4. The Principle of Dominance
  • Alleles

1. Alternative forms of genes.

2. Units that determine heritable traits.

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

5 dominant and recessive alleles
5. Dominant and Recessive alleles

Dominant alleles – upper-case

a. homozygous dominant

(BB – Brown eyes)

Recessive alleles – lower case

a. homozygous recessive

(bb – blue eyes)

b. Heterozygous (Bb – Brown eyes)

phenotype vs genotype
Outward appearance

Physical characteristics

Examples:

1.Brown eyes 2.blue eyes

Arrangement of genes that produces the phenotype

Example:

1. TT, Tt

2. tt

Phenotype vs. Genotype
7 recessive traits show up about 1 4 th of the time
7. Recessive traits show up about 1/4th of the time.
  • Because there is only a 25% chance that two recessive alleles will be paired together.
9 punnett square
9. Punnett square
  • A Punnett square is used to show the possible combinations of gametes.
  • Monohybrid Cross
monohybrid cross

B

b

male

gametes

B

Bb x Bb

b

female gametes

Monohybrid Cross
  • Example: Cross between two heterozygotesfor brown eyes (Bb)

BB = brown eyes

Bb = brown eyes

bb = blue eyes

monohybrid cross12

B

b

1/4 = BB - brown eyed

1/2 = Bb - brown eyed

1/4 = bb - blue eyed

BB

Bb

B

Bb x Bb

b

Bb

bb

1:2:1 genotype

3:1 phenotype

Monohybrid Cross
dihybrid cross14

RY

Ry

rY

ry

RY

Ry

rY

ry

Dihybrid Cross
dihybrid cross15

RY

Ry

rY

ry

Round/Yellow: 9

Round/green: 3

wrinkled/Yellow: 3

wrinkled/green: 1

RY

RRYY

RRYy

RrYY

RrYy

Ry

RRYy

RRyy

RrYy

Rryy

rY

RrYY

RrYy

rrYY

rrYy

ry

RrYy

Rryy

rrYy

rryy

9:3:3:1 phenotypic ratio

Dihybrid Cross
dihybrid cross16

RY Ry rY ry x RY Ry rY ry

possible gametes produced

Dihybrid Cross
  • Example: cross between round and yellow heterozygous pea seeds.

R = round

r = wrinkled

Y = yellow

y = green

RrYy x RrYy

10 independent assortment

This means all gametes will be different!

B

sperm

B

B

Bb

haploid (n)

b

b

diploid (2n)

b

meiosis II

meiosis I

10. Independent Assortment

B

F

  • Chromosomes separate independently of eachother

Bb

Ff

b

f

Bb

Ff

B

f

Bb

Ff

B

F

independent assortment
Independent Assortment
  • Genes for different traits can segretate independently during the formation of gametes without influencing eachother
  • Question: How many gametes will be produced for the following allele arrangements?
  • Remember: 2n (n = # of heterozygotes)

1. RrYy

2. AaBbCCDd

3. MmNnOoPPQQRrssTtQq

answer
Answer:

1. RrYy: 2n = 22= 4 gametes

RY Ry rY ry

2. AaBbCCDd: 2n = 23= 8 gametes

ABCD ABCd AbCD AbCd

aBCD aBCd abCD abCD

3. MmNnOoPPQQRrssTtQq: 2n = 26= 64 gametes

11 incomplete dominance

R

R

produces the

F1 generation

Rr

Rr

r

r

Rr

Rr

All Rr = pink

(heterozygous pink)

11. Incomplete Dominance
  • One allele is not completely dominant over another
11 codominance
11. Codominance
  • Both alleles are expressed
  • Example: blood

1. type A = IAIA or IAi

2. type B = IBIB or IBi

3. type AB = IAIB

4. type O = ii

Black cow + white cow = spotted cow

is cloning a possibility
Is cloning a possibility?
  • Is it right to use cloning to create an entirely new human being?
  • Is it ethical to create an embryonic copy of John Doe to supply cells to keep John alive?
  • Does a multicellular ball of tissue -- an embryo -- have the same rights and status as a human being?
how does mendel s principles apply to organisms
How does Mendel’s principles apply to organisms
  • The basic principals can be applied to humans as well as any other living organism.
and now it s time for
And now it’s time for….
  • Spongebob Genetics!!!!!