1. Introduction to Genetics

2. Heredity
the passing of traits from parents to offspring

3. Genetics
the branch of biology that studies heredity

4. Gene
piece of DNA that codes for a protein that is responsible for a trait
found on chromosomes

6. Genes

7. Gene
piece of DNA that codes for a protein that is responsible for a trait
found on chromosomes
basic unit of heredity

8. Trait
features of an organism
i.e. color of a flower

9. Allele different versions of a gene
i.e. purple or white flowers on a pea plant

10. Dominant
trait that is expressed even when another form of the trait is present
allele that shows itself in the presence of the other
usually represented with a capital letter
i.e. purple flowers in pea plants (P)

11. Recessive
trait that is not expressed when the dominant form of the trait is present
allele that is hidden in the presence of the other
usually represented with a lower case letter
i.e. white flowers in pea plants (p)

12. Dominant vs. Recessive

13. Homozygous both alleles for a trait are the same
can be homozygous dominant (PP, purple flowers) or homozygous recessive (pp, white flowers)

14. Heterozygous the alleles for a trait are different
a plant with one copy of the dominant gene (P, for purple flowers) and one copy of the recessive gene (p, for white flowers) would produce purple flowers (Pp)

15. Homozygous vs. Heterozygous

16. Genotype the combination of alleles an organism has for a trait
genotype = genes
Ex: PP, Pp, or pp

17. Phenotype the physical appearance of a trait phenotype = physical
Ex: purple or white

18. Monohybrid cross breeding that involves one pair of contrasting traits
i.e. breeding a purple-flowered plant with a white-flowered plant

19. True-breeding
breeding of organisms that will only produce offspring that have the same trait
i.e. a purple flower that will only produce purple-flowered offspring when bread with a similar purple flower

20. P generation parental generation
generally are true-breeding in controlled experiments
the first two individuals that mate in a genetic cross

21. F1 generation first filial generation
filialis – Latin, meaning “a son or daughter”
the offspring of a cross of two parents (P) in a genetic cross

22. F2 generation second filial generation
the offspring of a cross between two F1 individuals in a genetic cross
“grandkids” of the P generation from “inbreeding” the F1 generation

23. Thomas Andrew (T.A.) Knight (a little background information…)
A British horticulturist and botanist (plant scientist)
Lived
Most of his influential work was discovered after his death

24. Thomas Andrew (T.A.) Knight
bred a variety of true-breeding garden peas with purple flowers with a different variety of true-breeding garden peas white flowers (P generation)
all offspring (F1 generation) had purple flowers
when offspring were bred together, the next generation (F2 generation) had some purple flowers and some white flowers

25. Gregor Mendel

26. Gregor Mendel (a little background information…)
An Austrian monk
Lived
Trained as a mathematician and natural scientist.
First to present the principles of heredity.
Result of studying the inherited traits of peas over a period of eight years.
His work was published but overlooked by the scientists of his time (1865).

27. Gregor Mendel (a little background information…)
His work was rediscovered in 1900 after chromosomes had been named and their movements recorded in meiosis.
Observed that there was a perfect match between the observed behavior of chromosomes in meiosis and Mendel’s hypothesis of inheritance.

28. Gregor Mendel “father of modern genetics”
Mendel conducted work very similar to Knight’s work
Mendel counted the number of each kind of offspring in each generation
the data was then analyzed and used to make predictions about future generations

29. The Work of Gregor Mendel (a little background information…)
Holt Biology, pg. 163

30. The Work of Gregor Mendel (a little background information…)
Holt Biology, pg. 164

31. The Work of Gregor Mendel (a little background information…)
Holt Biology, pg. 163

32. Gregor Mendel
From his data analysis, Mendel created two Laws that helped him make predictions about future generations
Law of Segregation
Law of Independent Assortment

33. Law of Segregation
two alleles for a trait separate when gametes are formed
occurs because homologous chromosomes separate during Meiosis I

34. Law of Segregation & Meiosis

35. Law of Segregation

36. Law of Independent Assortment
the alleles of different genes separate independently of one another during gamete formation

37. Law of Independent Assortment

38. Law of Independent Assortment
the alleles of different genes separate independently of one another during gamete formation
occurs because different pairs of homologous chromosomes separate RANDOMLY during Meiosis I

39. Law of Independent Assortment
Holt Biology, pg. 163

40. The Work of Gregor Mendel (a little background information…)
Holt Biology, pg. 164

41. Theory Building
Mendel’s Laws pre-dated our modern understanding of meiosis
When new technologies were created to allow us to observe the steps of meiosis, they helped to confirm what had been predicted in theory

42. Summary
Why was Mendel’s work “more scientific” than Knight’s work?