1. Chapter 11: Introduction to Genetics

2. 11-1: The Work of Gregor Mendel
heredity: set of characteristics an organism receives from its parents
genetics: study of heredity

3. Gregor Mendel

4. Reproduction in Pea Plants
pollen is the male sex cell
eggs are the female sex cells
Able to reproduce….
self pollination: pollen fertilizes an egg from the same plant
cross pollination: pollen from one plant fertilizes an egg from another plant

5. Pea Plant Traits Seven traits with two options
Crossed plants with different characteristics of same trait
tall with short
green seeds with yellow seeds
round seeds with wrinkled seeds
alleles: different forms of a gene

6. True-Breeding
True-breeding plants are plants that only carry one allele for a trait.
If these plants are allowed to self-pollinate, they will produce offspring identical to themselves.
TALL plants produce TALL plants
Green seeded plants produce Green seeded plants

7. DO NOW DEC 12
If you crossed a wrinkled seeded pea plant with a round seeded pea plant, how would you predict the offspring produced?

8. DO NOW ANSWERED You would need to know which trait was dominant.
It is also necessary to identify the alleles from each parent that may be passed down to an offspring.
This dominant trait will most likely be expressed.

9. Mendel’s First Experiment
What did Mendel do in his experiments?
Prevented self pollination
Controlled cross pollination
Removed male flower parts
Pollen from plant A with egg from plant B
used purebreds
Seed color or plant height

10. Mendel’s Results
offspring were hybrids: organisms produced by crossing parents with differing characteristics
all hybrids had the characteristics of only one parent

11. Mendel’s Second Experiment
Crossed F1 hybrid plants
P generation: purebred group
F1 generation: hybrid group
F2 generation: offspring of hybrids
F2 plants - the recessive traits reappeared

12. Mendel’s Results Ratios of Mendel’s Crosses
phenotype: physical characteristics
genotype: genetic makeup
homozygous: two identical alleles for a particular trait
TT, homozygous dominant
tt, homozygous recessive
heterozygous: having two different alleles for the same trait Tt

13. Genes and Alleles genes: unit that determines traits
alleles: different forms of a gene
have two alleles for each trait
one from each parent
sex cells contain one allele
when sex cells combine, create cells with two sets of genes

14. Punnett Square Practice
Determine the possible genotypes of a pea plant that is Tall and has white flowers.
Tall is dominant over short
Purple is dominant over white flowers

15. Punnett Square Practice
Possible Genotypes
TT pp where T = Tall P = Purple
t = short p = white
Tt pp

16. Mendel’s Conclusions
1. individual factors, called genes, control each trait
2. principle of dominance: some factors or alleles are dominant whereas others are recessive

17. 11-2: Probability and Punnett Squares
probability applies to genetics because the formation of gametes depends on random events

18. Probability and Punnett Squares
probability: the likelihood that a particular event will occur
# of times event occurs ÷ by the total # of occurrences

19. Predicting Averages
Probabilities predict the average outcome of a large number of events.
Cannot predict the precise outcome of a single event.
Also true for genetics.
Larger numbers of offspring will produce results closer to the expected values/ratios.
Only 3 or 4 (F2) offspring may not equal the predicted ratio
However, hundreds/thousands of offspring will produce ratios very close to results.

20. Punnett Square Practice DEC 15
Solve the following problem…
Cross a Heterozygous Long-clawed panther with a short-clawed panther.
List all of the possible genotypes and their phenotypes.
What ratio of panther cubs have short claws?
What percentage?

21. Solution Dec 15
L = LONG CLAW DOMINANT
l = short claw L l Ll ll

22. Segregation the separation of alleles during gamete formation
New random combinations formed through meiosis
monohybrid cross: crossing one trait

23. Segregation What are the genotypes of the F1 plants?
When crossed, the recessive trait reappears in the F2 Gen

24. Independent Assortment
process by which genes separate independently of one another
Crossing of multiple traits
Dihybrid Cross

25. Dihybrid Crosses Solving for two different traits.
Parents --- RrYy and RrYy
R = Round seed Y = Yellow seed
Capital Letters = DOMINANT TRAITS
Use the FOIL method to determine all of the possible genotypes of the parents.
F=first O=outer I=inner L=last

26. Dihybrid Crosses Parent Genotypes – RrYy
Use FOIL Method to find possible allele combinations.
F – RY O – Ry I – rY L – ry
Allele Combinations – RY Ry rY ry

27. Dihybrid Crosses RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy

28. Review of Mendel’s Work
What information did Mendel’s experiments reveal about genetics?
Write your answers in your notebooks.
BE READY TO SHARE YOUR ANSWERS!

29. A Summary of Mendel’s Work
genes control heredity
genes are inherited from each parent
some forms of the gene may be dominant and others may be recessive
segregation occurs during the formation of reproductive cells
genes for different traits may sort independently of one another

30. 11-3: A Closer Look At Heredity
Incomplete dominance: neither allele is completely dominant or recessive
The phenotype for a heterozygous offspring is a blending of both alleles.

31. Incomplete Dominance
Cross a Red Flowered plant with a White Flowered plant.
What are the genotypes and phenotypes of the offspring?
What percent of the offspring will have White Flowers?

32. Punnett Square Solution

33. Codominance
codominance: both alleles are expressed and contribute to the phenotype
Example: Roan horse
CWCW  White Coat
CRCR  Red Coat
CRCW  Roan Coat
Cross a Roan Horse with a Red coated Horse.

34. DO NOW Answered DEC 17 CR CW x CR CR  RW x RR
NO. 0 out of 4 horses have a WHITE Coat.
What genotype identifies a WHITE Coat? R RR W RW

35. 11-5 Gene Linkage
Thomas Hunt Morgan conducted many experiments with the Drosophilia fruit fly.
Many groups of genes were “linked” together.
Reddish eyes and miniature wings
Two conclusions.
1. Chromosomes are actually groups of linked genes
2. Chromosomes assort independently (not single genes)

36. Polygenic Traits traits that are controlled by more than one gene
facial appearance

37. 11-5 Gene Mapping
Crossing over can separate and exchange linked genes.
Creates genetic diversity
The farther apart 2 genes are from one another, the greater chance they would be separated by crossing over.
Gene Locus –
Location of a gene on
a chromosome

39. Dihybrid Cross
Cross a homozygous Tall, heterozygous yellow seeded pea plant with a short, green seeded pea plant.
What percentage of the offspring will be tall and green seeded?

40. DO NOW ANSWER DEC 18 TY Ty ty
TtYy
Ttyy

41. Codominance
A farmer has been told by his friend that white-coated horses are worth more money than red or roan coated horses. He decides to breed his own by crossing two Roan coat horses.
Is he successful?
List the genotypes and phenotypes of all the offspring.
List the percentage of each phenotype.

42. Incomplete Dominance What is the genotype of a pink flower?
If two pink flowers were crossed, what are the possible genotypes and phenotypes of the offspring?