1. Biology I Turner College & Career High School 2017
Genetics & Heredity
Biology I Turner College & Career High School 2017

2. Fertilization is the fusion of an egg and a sperm.
Purebred (True breeding plants) are plants that were allowed to self- pollinate and the offspring will be exactly like the parent.

3. The Work of Gregor Mendel
Austrian monk
Born in 1822.
Studied heredity.
Heredity: the passing on of characteristics from parents to offspring.
Characteristics that are inherited are called traits.
First person to successfully predict how traits are transferred from generation to generation.
Used garden peas in his experiments.
The Father of Genetics

4. Mendel’s Work
Mendel carried out his work with garden peas.

5. Mendel’s Observations
Mendel noticed differences in:
Flower color
Flower position
Seed color
Seed shape
Pea pod shape
Pea pod color
Stem height
This led him to further experiment on the plants.

6. Why pea plants?
Reproduce sexually, which means that they produce male and female sex cells, called gametes.
In a process called fertilization, the male gamete unites with the female gamete.
The resulting fertilized cell, called a zygote, then develops into a seed.

7. Mendel’s Experiment
He took pollen from a male plant and dusted it onto a female plant.
Parental generation (p) = the original pair of plants
Offspring
(F1) = first filial generation
(F2) = second filial generation
His first experiments are called monohybrid crosses because they only deal with ONE single trait (height, color)
mono means “one”
Female
part
Transfer pollen
Pollen
grains
Male
parts
Cross-Pollination
The original parents, the true-breeding plants, are known as the P1 generation.
The offspring of the parent plants are known as the F1 generation.
When you cross two F1 plants with each other, their offspring are the F2 generation.

9. Mendel’s Experiments
Purebred: offspring where all previous generations have the same trait. Ex: a purebred short plant came from short parent plants.
First, he crossed a purebred purple with a purebred white.
Result of F1 Generation: all plants had purple flowers.
Parent Plants
F1 Generation

10. Mendel’s 2nd Experiment
Crossed two of the purple offspring from the F1 generation.
The F2 generation resulted in some offspring having purple flowers and others having white flowers
Parent Plants
F1 Generation
F2 Generation

11. Conclusions
Short pea plant Tall pea plant
All Tall pea plants
3 tall: 1 short P1 F1 F2
Each organism has two factors that control each of its traits.
These factors are genes and that they are located on chromosomes.
Genes exist in different forms called alleles.
The principal of dominance states that some alleles are dominant and others are recessive.
Tall pea plant
An organism’s two alleles are located on different copies of a chromosome—one inherited from the female parent and one from the male parent.

12. Tall pea plant Short pea plant
All tall plants F1 P1
Mendel called the observed trait dominant and the trait that disappeared recessive.
Mendel concluded that the allele for tall plants is dominant to the allele for short plants.
T T
t t T t
When recording the results of crosses, it is customary to use the same letter for different alleles of the same gene.
An uppercase letter is used for the dominant allele and a lowercase letter for the recessive allele.
The dominant allele is always written first.
T t

13. Law of Segregation F1
T t
T T 3
Tall
Short 1 F2
The way an organism looks and behaves is called its phenotype. Ex. Tall, yellow
The allele combination an organism contains is known as its genotype. Ex. TT, Tt
An organism’s genotype can’t always be determined by its phenotype.
Tt x Tt Cross
Tall
Tall
T t
T t
T t
t t

14. An organism is homozygous for a trait if its two alleles for the trait are the same. (True-breeding)
Exp. TT or tt
An organism is heterozygous for a trait if its two alleles for the trait differ from each other. (Hybrid)
Exp. Tt

15. Segregation Summary
Each trait has two genes, one from the mother and one from the father.
Traits can be either dominant or recessive.
A dominant trait only needs one gene in order to be expressed.
A recessive trait needs two genes in order to be expressed.
Egg and sperm are sex cells called gametes.
Segregation is the separation of alleles during gamete formation.

16. Genetics & Probability
Probability = the likelihood that a particular event will occur
Ex. Coin flipping: 1/2 probability that coin will flip head/tail
If you flip the coin 3 times what's the probability of flipping 3 heads?
1/2 x 1/2 x 1/2 = 1/8
*Past outcomes do not affect future ones!!*
The principles of probability can be used to predict the outcomes of genetic crosses.
What is the probability of parents having two male offspring in a row? (1/2 x 1/2=1/4)

17. Genetics & Probability
The likelihood that a particular event will occur is called probability.
Each trait has two genes, one from the mother and one from the father.
Alleles can be homozygous; having the same traits.
Alleles can be heterozygous; having different traits.

18. Question 1
The passing on of characteristics from parents to offspring is __________.
A. genetics
B. heredity
C. pollination
D. allelic frequency
The answer is B.
Genetics is the branch of biology that studies heredity.

19. Question 2 What are traits? Answer
Traits are characteristics that are inherited. Height, hair color and eye color are examples of traits in humans.

20. Question 3 Gametes are __________. A. male sex cells
B. female sex cells
C. both male and female sex cells
D. fertilized cells that develop into adult organisms
The answer is C.
Organisms that reproduce sexually produce male and female sex cells, called gametes.

21. Question 4
Which of the following genotypes represents a animal that is homozygous dominant for a trait?
a. KK
b. Kk
c. kk

22. Question 5
Which of the following genotypes represents a plant that is homozygous recessive for height?
a. TT
b. Tt
c. tt

23. Punnett Squares
The gene combination that might result from a genetic cross can be determined by drawing a diagram known as a Punnett square.
These are used to predict and compare the genetic variations that will result from a cross.
The types of gametes go on the top and left sides of the square.
The possible gene combinations appear in the four boxes.

24. Punnett Squares
If you know the genotypes of the parents, you can use a Punnett square to predict the possible genotypes of their offspring.

25. Making a Punnett Square

26. You try this one… A a A a AA Aa

27. More Practice
For a gene determining hair color (B); where both parents are heterozygous for blue hair.
B = dominant allele; blue hair
b = recessive allele; yellow hair
Parent 1 = Bb B b BB Bb bb
Parent 2 = Bb
Possible Children
Possible Children: ½ (50%) Bb = blue hair
¼ (25%) BB = blue hair
¼ (25%) bb = white hair

28. Exploring Mendelian Genetics
Independent Assortment
Genes segregate independently.
The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes.
Independent assortment helps account for the many genetic variations observed in plants, animals and other organisms.

30. Summary of Mendel’s Principals
Genes are passed from parent to offspring. 
Some forms of a gene may be dominant and others recessive.
In most sexually producing organisms, each adult has two copies of each gene: one from each parent. These genes are segregated from each other when gametes are formed.
The alleles for different genes usually segregate independently of one another.

31. Beyond Mendel: Dominant & Recessive Alleles
Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.
Cases in which one allele is not completely dominant over another are called incomplete dominance.
Example: White (W) and Red (R) are both dominant in a flower. If WW x RR the F1 generation would be WR = pink.

32. Incomplete Dominance
Incomplete: Think PINK!

33. Co-dominance
Codominance is when both alleles contribute to the phenotype.
Examples: Feathers, flowers, cattle.

34. Polygenic Inheritance
Polygenic inheritance refers to the kind of inheritance in which the trait is produced from the cumulative effects of many genes.
In humans, height, weight, and skin and eye color are examples of polygenic inheritance

35. MEIOSIS
A type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

36. Review: Characteristics of Living Things
Living things are made up of cells.
Unicellular: one celled organisms.
Multicellular: many celled organisms.

37. Review: Characteristics of Living Things
Living things reproduce to make offspring of the same species.
Asexual reproduction
Sexual reproduction

38. Review: Characteristics of Living Things
Living things grow and develop

39. What type of cell division is the diagram above?
What phase of cell division the arrow pointing to?

40. Meiosis is Reduction Division
Chromosome number is cut in half by separation of homologous chromosomes in diploid cells

41. Meiosis Every individual has two sets of chromosomes.
One from the mother; one from the father.
When the chromosomes pair up for the same trait they are called homologous chromosomes.
A cell that contains pairs of homologous chromosomes is said to be diploid or 2n.
Gametes (egg /sperm) have only one chromosome and are said to be haploid or n.

42. Phases of Meiosis
Meiosis is a process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell. 
Meiosis I: The homologous chromosomes line up but, then they crossover, exchanging genetic information.
Meiosis II: The two cells produced now enter a second division.
Start with 2 the two new cells and get 4 different cells each with 23 chromosomes.

43. Crossing Over
Chiasmata: site of crossing over, occur in synapsis. Exchange of genetic material between non-sister chromatids.
Crossing over produces recombinant chromosomes.
Results in variations in daughter cells.

44. Chromosome Number in Body Cells vs. Gametes
Haploid (n) - have 1 set
Body Cells
Diploid (2n) - have 2 sets

45. Meiosis I
Meiosis II
Crossing Over

46. Results of Meiosis 4 haploid (n) cells.
Genetically different from each other & the original cell.

47. Variation
During normal cell growth, mitosis produces daughter cells identical to parent cell (2n to 2n)
Meiosis results in genetic variation by shuffling of maternal and paternal chromosomes and crossing over.
No daughter cells formed during meiosis are genetically identical to either mother or father
During sexual reproduction, fusion of the unique haploid gametes produces truly unique offspring.

48. Human Cells 2n=46. Sperm Cell Egg Cell White Blood Cell 23 chromosomes
Gamete is haploid (n)
Egg Cell
White Blood Cell
46 chromosomes
Body cell is diploid (2n)