1. Mitosis and Meiosis

2. Pure Breeds The puppies of purebred dogs will grow up to look very much like their parents.

3. Mixed Breeds However when the parents are of a mixed breed, the final sizes, markings, and builds of these puppies, as well in their behavioral traits, will be more varied.

4. Dog Genetics
But whether dogs are purebred or mutts, we can ultimately explain their innate traits by using genetics, the science of heredity.
Because of inbreeding, purebred dogs often suffer from serious genetic defects.
For instance, a type of hereditary blindness called progressive retinal atrophy is common among Labrador retrievers, spaniels, and several other breeds.
About 60% of the genetic disorders in dogs are similar to human genetic diseases, so genetic researchers often examine the genetic problems of dogs.

5. Dog Genetics In 2003, researchers completed the entire genome (genetic sequence) of dog DNA. This project is yielding a wealth of data that can be used to compare the DNA of humans and dogs.

6. Dog Genetics
Biologists are also studying certain dog breeds to shed light on the relationship between genetic makeup and behavior.
Dogs of different breeds tend to have different temperaments. Pit bulls and Rottweilers, for instance, are more likely to be aggressive than some other breeds because they were bred as guard dogs: in generation after generation, the most aggressive dogs were selected for mating with each other.
In fact, selective breeding is the basis for many of the dog breeds that exist today.

7. Dogs are descendants of wolves It is estimated that until about 14,000 years ago, dogs were very much like wolves, the species from which dogs evolved.

8. Dog Genetics
It was at this time that dogs began to move with people into more permanent settlements, which were often geographically isolated.
As a result, different populations of dogs became isolated from one another and eventually became inbred.
At the same time, different groups of people selected dogs for different traits, depending on their needs.

9. Dog Genetics
Herders selected dogs that were good at controlling flocks of animals, producing breeds such as the Border collie.
Hunters had developed breeds of dogs, such as the laboratory retriever, which are good at retrieving wounded prey.
Such dogs were bred to be less aggressive than some other breeds because hunters don't want their dogs to eat the quarry!

10. Dog Genetics
Genetics isn't everything: a dog’s level of aggression and other behavioral characteristics are influenced not only by its genes but also by its environment and care.
The same is turning out to be true of human behavioral characteristics.
Traits such as shyness have some genetic basis but can also be amplified or reduced by upbringing.

11. Mitosis
Before you can begin to understand the rules that govern how inherited characteristics are passed from parent to offspring, you need to understand the basic biological concept of how chromosomes behave during the fertilization of an embryo.
Therefore, we will first cover mitosis, how cells divide.

12. Chromosomal Inheritance
Mary was a very attractive young woman who liked to play ice hockey.
Her high school gym teacher took an interest in her ability and gave her extra coaching.
She hoped that one day Mary would play on an Olympic team.
But something was wrong. Mary was sixteen and still not menstruating.
Her parents decided to have her undergo a series of medical tests.
Much to the surprise of everyone, Mary had an X and Y chromosome in the nucleus of her cells.
She was a chromosomal male.

13. Chromosomal Inheritance
The doctor explained to Mary and her parents that Mary had testicular feminization syndrome.
She has internal testes that produce testosterone but her cells won’t respond to it.
Her genitals are like those of a female and she has well-developed breasts.
However, she will never be able to have children.
Mary will be able to go on and play hockey in the Olympics but she has to always carry a letter explaining her condition. Otherwise she will be disqualified because of her sex chromosomes.

14. Karyotyping
In the nucleus of a cell there are chromosomes, arranged in pairs which are joined in the center.
Each of these pairs are called a called a karyotype (type of chromosome pair).
Humans have 23 pairs of chromosomes.
When they are taken out of a cell for genetic testing, scientists arrange the pairs in order of their assigned name (which is a number from 1-23).
This procedure is called karyotyping.

15. Sex Chromosomes Males are called XY Females are called XX.
Males have one pair of chromosomes that are not the same length. The larger chromosome in this pair is the X chromosome and the smaller is the Y chromosome. Females have two X chromosomes. This pair is called the sex chromosomes because they contain the genes that determine the sex.
Males are called XY
Females are called XX.
The male is the parent that determines the sex of the child.

16. GENES
Genes are the structures constructed of DNA that control the characteristics of the individual
Genes are like small dots on each chromosome. Each dot contains the blueprint for some aspect of the body. One gene is for eye color, one for liver function, one for right or left handedness, etc. Every aspect of the body corresponds to a gene on one of the chromosomes.

17. Human Cell Division
All cells in our body divide by a process called mitosis
Mitosis produces two daughter cells with the same number and kind of chromosomes as the parent cell.
If a parent cell has 7 chromosomes prior to mitosis, how many chromosomes will the daughter cells have?
Answer = 7.

18. Sex Cells
In addition to mitosis, the sex cells (and only the sex cells) undergo a second process called meiosis.
Meiosis: each daughter cell has only half of the chromosomes.
In males, it produces the cells that become sperm
In females, it produces the cells that become eggs.
The sperm and the egg are the sex cells, or gametes.
GAMETES contain half the number of chromosomes compared to the rest of the body cells.

19. Sex Cells
Therefore, meiosis requires two nuclear divisions, resulting in four daughter cells, each with half of the parent chromosomal number
 When a sperm cell fertilizes an egg, the resulting zygote has the all of the chromosomes from each of the sex cells, for a total of 46 (or 23 pairs). Thereafter, when the cells of the zygote/embryo/fetus/infant/child/adult divide by mitosis, each cell has 23 pairs of chromosomes.

21. Mitosis Video Clip

22. Stages of Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase

23. Mitosis Overview Video

24. Interphase
The chromosomes make an identical clone of themselves within the nucleus.
For a human with 46 chromosomes, they now have 92 chromosomes (just for a few minutes!).
The clone is joined to the original at the middle so they look like an “X”.

25. Interphase

26. Interphase Video Clip

27. Prophase
The nuclear envelope dissolves away, and the chromosomes are released into the cytoplasm of the cell.
The chromosome pairs start to shorten and thicken as they get ready to separate.

28. Prophase

29. Prophase Video

30. Metaphase
During metaphase, the chromosomes line up at the center of the cell.

31. Metaphase

32. Metaphase Video Clip

33. Anaphase
At the start of anaphase, the sister chromosomes separate and move toward opposite sides of the cell.
There will now be 23 chromosomes on each side of the cell.

34. Anaphase

35. Anaphase Video Clip

36. Telophase Telophase begins when the chromosomes arrive at the poles.
A nuclear envelop now forms around each set of chromosomes, so at this phase, the parent cell has two nuclei, each with a complete set of chromosomes.
Telophase is characterized by the formation of two daughter nuclei.
At the very end of telophase, the cell membrane pinches in two (cytokinesis) so that there are two new cells.

37. Telophase

38. Telophase Video Clip

39. Cytokinesis Video Clip

41. Video Clip of Animal Mitosis

42. MEIOSIS
Meiosis only occurs in the testes and ovaries when they are ready to make an egg cell or a sperm cell.
First, mitosis occurs as normal.
But right after that, the two daughter cells divide again, but this time there is no prophase, so the chromosomes have not made a clone of themselves.

43. Crossing Over
When the second cell division is at the metaphase stage, the chromosomes touch each other and exchange a few genes.
The exchange of genetic material between chromatids is called crossing-over.
That is what allows for genetic variation.

44. Crossing Over

45. Crossing Over Video Clip

46. MEIOSIS
Meiosis results in four daughter cells, each having half the number of chromosomes as the parent cell.
The daughter cells are not genetically identical, and neither is identical to the parent cell.
For example, in MEIOSIS, if the parent cell has 14 chromosomes, the GAMETE will have 7.

47. Gametes to Zygote
When a sperm and egg (gametes) combine and contribute their chromosomes, the fertilized egg (called a zygote) will now have 23 pairs of chromosomes.

48. Nondisjunction
Chromosomes can become abnormal if the sister chromosomes do not separate properly during meiosis.

50. Video Clip of Blastula

51. Video Clip of Neural Tube

52. Biotechnology Dog Genetics Plants that fight air pollution
(90 mins, start at 15)
Plants that fight air pollution
(23 mins)
Biotechnology Products
(4 mins)
Biotechnology Techniques
(14 minutes)

53. Preventing Birth Defects: Discussion

54. Maternal Health Habits: Discussion

55. Fertilization with 20 year old sperm: Discussion