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Observable Patterns of Inheritance Starr/Taggart’s Biology: The Unity and Diversity of Life, 9e Chapter 11 Edited by: R. LeBlanc, M.S. Mountain Pointe High School 2012

Observable Patterns of Inheritance

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Observable Patterns of Inheritance. Edited by: R. LeBlanc, M.S. Mountain Pointe High School 2012. Starr/Taggart’s Biology: The Unity and Diversity of Life , 9e Chapter 11. Charles Barkley. Tom Cruise. What do Charles Barkley and Tom Cruise have in common? (hint: check out their ears). - PowerPoint PPT Presentation

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Page 1: Observable Patterns of Inheritance

Observable Patterns of Inheritance

Starr/Taggart’s Biology:

The Unity and Diversity of Life, 9e

Chapter 11

Edited by: R. LeBlanc, M.S.

Mountain Pointe High School

2012

Page 2: Observable Patterns of Inheritance

Fig. 11.1, p. 174

Tom Cruise Charles Barkley

Gregor Mendel Joan Chen

What do Charles Barkley and Tom Cruise have in common? (hint: check out their ears).

Page 3: Observable Patterns of Inheritance

Terms Used in Genetics

Genes Alleles Hybrid Homozygous Heterozygous Dominant Recessive Genotype Phenotype Generations

P, F1, F2

Page 4: Observable Patterns of Inheritance

Plant Reproductive Organs

Page 5: Observable Patterns of Inheritance

carpel stamen

GAMETES - the male or female sex cells. In plants, the sperm is the male sex cell (found in pollen grains), and the ovule (egg) is the female sex cell.

PISTIL – female reproductive structure.

STAMEN – male reproductive structure.

FERTILIZATION- the uniting of the male and female gametes within the flower.

POLLINATION - The transfer of pollen from the anther to the pistil, usually by wind, water, or insects.

CROSS-POLLINATION - transferring the pollen from one plant to another plant.

Plant Reproductive Terms

Page 6: Observable Patterns of Inheritance

Mendel identified Mendel identified sevenseven traits in his garden peas traits in his garden peas that were easily studied:that were easily studied:

SEED SHAPESEED SHAPE

SEED COLORSEED COLOR

POD SHAPEPOD SHAPE

POD COLORPOD COLOR

FLOWER COLORFLOWER COLOR

FLOWER POSITIONFLOWER POSITION

STEM LENGTHSTEM LENGTH

roundround wrinkledwrinkled

yellowyellow greengreen

inflatedinflated wrinkledwrinkled

greengreen yellowyellow

purplepurple whitewhite

axialaxial terminalterminal

talltall dwarfdwarf

He carefully isolated He carefully isolated pure pure breedingbreeding varieties before varieties before

experimenting with experimenting with crosses between different crosses between different

varieties.varieties.

Page 7: Observable Patterns of Inheritance

Mendel’s Insight Into Patterns of Inheritance

Mendel’s Experimental Approach Garden pea plant

Cross pollination

What are the advantages of SELF cross pollination?

What is the advantage of using pea plants?

How did Mendel control his experiments?

Page 8: Observable Patterns of Inheritance

Mendel’s Experiment

Page 9: Observable Patterns of Inheritance

Mendel concluded that each organism has two factors (alleles) for each trait.

He performed crosses with seven different pairs of traits (for example, pure-breeding purple-flowered plants crossed with pure-breeding white-flowered plants). In every case he found that one trait disappeared from the F1 generation only to

reappear in the F2 generation plants!

This is explained by the Rule of Dominance which will be demonstrated in the next two examples:

Page 10: Observable Patterns of Inheritance

Mendel’s Theory of Segregation

Monohybrid cross Gene

segregation

What do you notice about the alleles of both parents?

What do the letters A & a stand for? (the font of the letters)

What are diploid gamete cells? Haploid?

Why are the final gamete cells haploids?

What does the fertilized zygote traits represent? (check the alleles)

Page 11: Observable Patterns of Inheritance

Probability and Punnet Squares

A possibility of outcomes and crossesTest crosses

Unknown genotype crossed with homozygous recessive

Page 12: Observable Patterns of Inheritance

Mendel’s Monohybrid Cross

Pure White Flower

Pure Purple Flower

What traits (genotype) do F1 offspring have?

Page 13: Observable Patterns of Inheritance

Mendel’s Monohybrid Cross

What percentage of the second generation are purple? White?

What % are pure purple? White?

If you planted four first generation seeds , how many of these seeds will be purple flowers in the 2nd generation?

Page 14: Observable Patterns of Inheritance

ChapterChapter 9 9

Mendel’s Conclusions

Section 1 Mendel’s Legacy

Page 15: Observable Patterns of Inheritance

Trait Studied Dominant Form

Recessive Form

F2 Dominant-to- Recessive Ratio

SEED SHAPE

SEED COLOR

POD SHAPE

POD COLOR

FLOWER COLOR

FLOWER POSITION

STEM LENGTH

2.96:1

3.01:1

2.95:1

2.82:1

3.15:1

3.14:1

2.84:1787 tall 277 dwarf

651 long stem

207 at tip

705 purple 224 white

152 yellow428 green

299 wrinkled882 inflated

6,022 yellow 2,001 green

5,474 round 1,850 wrinkled

Fig. 11.5, p. 178

To get the ratios on the right to all be approximately equal, what do we know about the P1 plants?

What do you notice about the number of plants studied?

How did Mendel decide which of the traits were dominant? Recessive?

Why aren’t the ratios exactly 3:1?

Page 16: Observable Patterns of Inheritance

Independent Assortment

Page 17: Observable Patterns of Inheritance

In-text, p. 180

AABB aabb

x

AaBb

AB AB ab ab

TRUE-BREEDING PARENTS:

GAMETES:

F1 HYBRID OFFSPRING:

purple flowers, tall

white flowers,dwarf

What are the phenotype ratios of all the offspring resulting from the cross of these 2 parents? Genotype?

ALL F1 OFFSPRING: PURPLE TALL

GENOTYPE: AaBb

What about the phenotype ratio of the offspring of the F2 generation?

9 : 3 : 3: 1

http://www.biology.arizona.edu/mendelian_genetics/mendelian_genetics.html

Use the website above for practice genetics problems.

Page 18: Observable Patterns of Inheritance

Fig. 11.9, p. 181

aB

AB

AB

abAb

Ab

aB

ab

1/4

1/4

1/4

1/4

1/4 1/4 1/4 1/4

AB ab

AABBpurple-

floweredtall parent

(homozygousdominant)

aabbwhite-

flowereddwarf parent(homozygous

recessive)

F1 OUTCOME: All F1 plants purple-flowered, tall(AaBb heterozygotes)

X

meiosis, gamete formation

AaBb AaBb

Possible outcomes of cross-fertilization

AaBb aabbAabb aaBb

AABB AABb AaBB AaBb

AABb AAbb AaBb Aabb

AaBb aaBB aaBbAaBB

1/161/161/161/16

1/161/161/161/16

1/161/161/161/16

1/16 1/16 1/16 1/16

ADDING UP THE F2 COMBINATIONS POSSIBLE:

9/16 or 9 purple-flowered, tall

3/16 or 3 purple-flowered, dwarf

1/16 or 1 white-flowered, dwarf

3/16 or 3 white-flowered, tall

Page 19: Observable Patterns of Inheritance

Theory in Modern Form

Independent Assortment

Gametes require genes independently of how other pairs of genes were sorted out

Variety of Offspring

Page 20: Observable Patterns of Inheritance

A cross where one allele does not completely hide or mask the other producing a blended appearance in the phenotype.

Example: In snapdragons, pure red crossed with pure white produce pink!

INCOMPLETE DOMINANCE INCOMPLETE DOMINANCE

Page 21: Observable Patterns of Inheritance

CODOMINANCECODOMINANCE

Two non-identical alleles of a pair specify two different phenotypes yet one cannot mask the other and both are expressed .

Page 22: Observable Patterns of Inheritance

Multiple Alleles

More than two alleles in a population for a given trait.

Example: human blood types.

3 alleles: A,B,O. What do the letters

A, B & O stand for? A & B stand for a

type of protein found on the surface of RBC and i stands for the lack of this protein.

Page 23: Observable Patterns of Inheritance

Multiple Effects of Single Genes

Pleiotropy. The expression of

a single gene can influence two or more traits.

Sickle Cell Anemia.

What do you notice about the physical effects of having sickle cell anemia?

*Refer to the next slide

Page 24: Observable Patterns of Inheritance

Fig. 11.12, p. 183

HbA = Normal Red Blood Cells HbS = Sickle Cell Red Blood Cells

To develop the full effects of Sickle Cell Anemia you need to be Homozygous for this trait.

Page 25: Observable Patterns of Inheritance

Interactions Between Gene Pairs

Epistasis

Fur color in mammals

Melanin production

Albinism Comb shape in chickens (see the example

in the next slides)

(When 1 gene pair influences other gene pairs with their combined activities producing some effect on phenotype)

(Melanin produces fur color)

(influenced by an enzyme produced from the alleles from another gene)

(the absence of melanin)

Page 26: Observable Patterns of Inheritance

Fig. 11.15, p. 185

WALNUT COMB

9/16 walnut(RRPP, RRPp, RrPP, or RrPp)

ROSE COMB

3/16 rose(RRpp or Rrpp)

PEA COMB

3/16 pea(rrPP or rrPp)

SINGLE COMB

1/16 single(rrpp)

RRpp(rose comb)

rrPP(pea comb)

RrPp(all walnut comb)

comb

P:

F2:

F1:X

X

NOTE: Sometimes interaction between 2 gene pairs results in a phenotype that neither pair can produce alone. Comb shape in chickens can result in 4 types depending on the interactions of 2 gene pairs (R & P)

Epistasis Problem: Cross a Rose Comb (RRpp) chicken with a Pea (rrPP) Comb chicken. What will be the phenotype ratio of the off-spring? Cross this F1 generation. (R = Rose Comb; P = Pea Comb; RP = Walnut Comb; and rp = Single Comb)

Page 27: Observable Patterns of Inheritance

Fig. 11.14, p. 185

In some individuals the 2 genes mentioned earlier do NOT interact, causing another gene to effect coloration. At gene ‘C’, a gene at another gene locus, is responsible for the enzyme called tyrosinase, one of many enzymes responsible for the production of melanin. An individual with one of the dominant alleles (CC or Cc) can make the functional enzyme. If two recessive alleles (cc) are present, melanin production is interfered with resulting in ALBINISM.

What causes this Albino snake??????

Page 28: Observable Patterns of Inheritance

The alleles of one gene specify an enzyme for melanin production while an allele on another gene is

responsible for the deposit of melanin in the

hairs of the organism.

B = BLACK b = BROWNE = Full deposit ee = Reduced Deposit produces a Golden color (in B or b)Black Golden Brown

Epistasis Problem: Cross homozygous Black Lab with a Gold Lab (bbee) What would be the off-springs phenotype ratio of a cross between 2 F1 generation off-spring? List the different genotypes of each phenotype represented?

(BBEE; BBEe; BbEE; BbEe)

(bbEE; bbEe)

(BBee; Bbee; bbee)

Page 29: Observable Patterns of Inheritance

Less Predictable Variation in Traits

Camptodactyly (A

rare genetic abnormality the affects both the shape and the movement of fingers. This can be caused by improper enzyme production.)

Continuous variation (A range of

small differences in the phenotypes of individuals)

Eye color

Height

Page 30: Observable Patterns of Inheritance

Fig. 11.16, p. 186

Eye Color:

-iris (eye color) is beneath the cornea.

-Color: a cumulative outcome of a number of gene products

-Melanin production affects color.

-Dark eyes = increased amounts of melanin.

-Brown eyes = less melanin.

-Light brown/hazel = even less

-Gray/green/blue = very little melanin, so these wave lengths of light are reflected back to the observer.

Continuous Variation:

-Different pairs of genes (alleles) interact to produce and deposit melanin.

-Eye color seems to be Continuous; from

Black ------------- Blue

(+ melanin - melanin)

Page 31: Observable Patterns of Inheritance

Examples of Environmental Effects on Phenotypes

Himalayan Rabbit & Siamese Cat Less melanin in warm body regions. Heat

makes enzyme in melanin production pathway less active

Hydrangea color Color ranges from blue to pink,

depending on acidity of soil

Page 32: Observable Patterns of Inheritance

In Conclusion

Gene is unit of information about a heritable trait

Mendel provided indirect evidence of dominant and recessive genes

F1 offspring form monohybrid crosses

AA x aa -----> Aa

Crosses from F1 result in F2 offspring

with phenotypes having a 3:1 ratio

Page 33: Observable Patterns of Inheritance

In Conclusion

Theory of segregation states that genes of each pair segregate during meiosis and wind up in different gametes

Dihybrid crosses result in 9:3:3:1 phenotypic ratio

Theory of Independent Assortment states that gene pairs independently sort out into different gametes regardless of other gene pairs of other chromosomes

Page 34: Observable Patterns of Inheritance

In Conclusion

Four factors influence gene expression

Degrees of dominance

Products of pairs of genes may interact

One gene may effect two or more traits

Environment