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 AA, bb
Only have one allele per trait
AA, bb
What is another name for a true-breeding plant?
Only produce identical offspring
TALL plants produce TALL plants
Green seeded plants produce Green seeded plants

7. 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

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

9. 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

10. 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

11. 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

12. DO NOW DEC 8 Solve the following problem…
Cross a Heterozygous Long-clawed panther with a short-clawed panther.
1. List all of the possible genotypes and their phenotypes.
2. What percentage of panther cubs will have short claws?

13. Solution Dec 8 L l Ll ll L = LONG CLAW l = short claw
Genotype = Ll Phenotype = LONG claw
ll short claw
% Genotype ll L l Ll ll

14. Independent Assortment
Principle in which alleles separate independently of one another as they are passed down from parent to offspring.
Interpret this statement.
How does this process occur?
Why is this process valuable to a species?

15. Independent Assortment
Interpret this statement.
The passing down of alleles is a random process.
How does this process occur?
Meiosis
Crossing over, Independent Association, Gamete Formation in Females
Why is this process valuable to a species?
Provides Genetic Variation to organisms.
Necessary for survival.

16. Interpreting Genotypes and Phenotypes
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

17. Identifying Genotypes
Possible Genotypes
TT pp where T = Tall P = Purple
t = short p = white
Tt pp

18. Dihybrid Crosses
Perform a cross between two heterozygous round and heterozygous yellow seed plants.
R = Round seed Y = Yellow seed
r = wrinkled seed y = green seed
What do you need to determine from the information you are given?

19. Dihybrid Crosses Solving for two different traits. Parents RrYy x RrYy
R = Round seed Y = Yellow seed
r = wrinkled seed y = green seed

20. F=first O=outer I=inner L=last
Allele Combinations
Use the FOIL method to determine all of the possible genotypes of the parents.
F=first O=outer I=inner L=last

21. Allele Combinations Parent Genotypes – RrYy
Use FOIL Method to find parent allele combinations.
F – RY O – Ry I – rY L – ry
Allele Combinations RY Ry rY ry

22. Analyzing Results
Answer the following question using your Punnett Square results.
What is the ratio of offspring having a
round and green seed?

23. Identifying the Phenotypes of the Offspring
Parent Allele Combinations RY Ry rY ry
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy

24. Step by Step Procedure 1. Identify the parent genotypes
2. Assign letters to represent alleles
3. Use FOIL to determine allele combinations
4. Set up and Solve your Punnett Square
5. Identify information you need to answer questions.
Write down genotypes / phenotypes
6. Analyze data from the results of your Punnett Square.
Calculate genotypic and phenotypic ratios
Answer questions using results

25. Punnett Square REVIEW
A poodle that is heterozygous for white, curly fur is crossed with a poodle having black, straight fur.
What are the chances one of their puppies will have white, straight fur?

26. WwCc x wwcc
Parent Allele Combinations WC Wc wC wc
WwCc
Wwcc
wwCc
wwcc

27. Punnett Square REVIEW
What are the chances one of their puppies will have white, straight fur?
White Curly DOMINANT
Genotypes for White, Straight fur
WWcc or Wwcc
4/16 puppies

28. 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

29. 11-2: Probability and Punnett Squares
probability applies to genetics because the formation of gametes depends on random events

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

31. 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.

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

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

34. 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

35. Dihybrid Crosses Homework Review
Question 3 BE Be bE be
BbEe
Bbee
bbEe
bbee

36. Dihybrid Crosses Homework Review
Question 6 TP Tp
TTPp
TTpp tp
TtPp
Ttpp

37. 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.

38. 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?

39. Punnett Square Solution Incomplete Dominance

40. 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.

41. Solution CR CW x CR CR  RW x RR How many horses have a white coat? R

42. Multiple Alleles Polygenic Traits
a trait that has more than two alleles
eye color
blood type
traits that are controlled by more than one gene
facial appearance

43. Multiple Alleles Polygenic Traits
Blood types in humans. A B AB O
ALLELES: A, B, O
Coat color in rabbits
Four different alleles
Skin color in humans
Eye color is various organisms
Fruit flies

44. BLOOD TYPES Controlled by 3 Alleles A and B are codominant
A (IA), B (IB) and O (ii)
A and B are codominant
Both dominant over O

45. Blood Type Punnett Squares

46. 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)

47. 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

49. 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.

50. 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?