1. Homework:
For tomorrow:
Read 6.1 do FAQ # 2
Read 6.2 do FAQ # 4

2. Genetics
Unit 3
Ch. 6-9

3. Sexual Reproduction and Meiosis
Ch. 6.1 – 6.2

4. Lesson Objectives At the end of this lesson, students will be able to…
Explain the difference between somatic cells and gametes in terms of genetics and function
Compare and contrast mitosis and meiosis in terms of the process, genetics, and products

5. Asexual vs. Sexual Reproduction
We have already learned that cell division by mitosis results in cells that are identical to the parent – Asexual reproduction also results in organisms identical to the parent
In order to create UNIQUE individuals, organisms use a process called meiosis and sexual reproduction

6. Meiosis
Meiosis – this process is very similar to mitosis but it requires two rounds of division and results in gametes containing only half the chromosomes of the parent
Remember: Meiosis makes gametes

7. Vocabulary
Somatic cells – these are the cells that make up everything in our body, they reproduce by mitosis
Diploid cells – these are cells that contain a double set of chromosomes (in humans this would be 46 since n = 23), the short hand for this is 2n, somatic cells are diploid

8. Vocabulary
Gametes – these are sperm and egg cells, also called sex cells, they contain half of each parent’s chromosomes, they are produced by meiosis
Haploid cells – these cells only contain half the chromosomes of the parent cells, gametes are haploid, the shorthand for this is 1n

9. Vocabulary
Gametogenesis – “making gametes,” gametogenesis is the process that matures haploid cells made by meiosis into gametes

10. Mitosis vs. Meiosis
During mitosis, a cell simply grows and divides to create an exact copy of itself
During meiosis, the cells created are genetically different from the parent cells due to a mixing and shuffling of chromosomes during division

13. Mitosis Vs. Meiosis Mitosis Meiosis DNA Replication Rounds of Division
During interphase before mitosis starts
During interphase before meiosis starts
Rounds of Division
One
Two
Number of Daughter Cells
Four
Genetic Composition
2n (diploid)
1n (haploid)
Role in the Animal Body
Somatic cells, makes up tissues and organs
Gametes, sex cells (eggs and sperm)

14. Meiosis: Making Gametes
Gametes are produced from cells called germ cells located in the gonads of sexually reproducing organisms.
The first round of division separates homologous chromosomes

15. Vocabulary
Homologous Chromosomes – homologous means “matching” – we get half of our chromosomes from each parent so we end up with 2 copies of each chromosome (2n). The matching copies are the homologous chromosomes.

16. (During S Phase)

17. Are homologous chromosomes identical to each other?
Discuss:
Are homologous chromosomes identical to each other?
Explain.
No, they are very similar in size and type of genes but since they were inherited from different parents, they carry different versions of genes.

19. How does meiosis make gametes?
It takes two rounds of division to produce haploid gametes
Meiosis I – homologous pairs of chromosomes separate and are put into two different cells
Meiosis II – the sister chromatids of the chromosomes separated in meiosis I are separated and put into different cells
The final result is 4 daughter cells containing 1 sister chromatid from each of the original chromosomes
Because DNA gets shuffled, each daughter cell has a different genetic combination

20. Gametes

21. Meiosis Video Things that are similar to mitosis
Things that are different from mitosis

22. Paperclip Meiosis!!
Use packet to start

23. Why are gametes important?
When most animals reproduce, it requires a male and female
Each parent donates a gamete carrying half of their chromosomes
These gametes fuse (fertilization) and the two half sets of DNA combine to form a diploid cell
That diploid cell then divides, multiplies, differentiates and eventually becomes a baby

24. Meiosis: Making Gametes
After homologous chromosomes have been separated into 2 daughter cells, the next round of division can start
During the second round, sister chromatids are separated – This results in FOUR HAPLOID cells
These haploid cells are gametes – sperm or eggs

25. Why is it important that gametes are haploid cells?
Discuss:
Why is it important that gametes are haploid cells?

26. Why are gametes important?
We get 22 regular chromosomes from each parent – these are called autosomes
We also get 1 sex chromosome from each parent – and X or a Y – this determines if we will be male or female
XX = girl
XY = boy
This results in a total of 46 chromosomes (in humans)

27. Page 162: Data Analysis
Working on your own or with a neighbor, look at the graphs and answer 1 - 3

28. Meiosis I and II
Meiosis
Using fig 2.3 on pg. 164 or the link above, make a Venn Diagram to compare meiosis I and II

29. Homework: Catch up: For tomorrow: Read 6.1 do FAQ # 2

30. Heredity, Traits, Genes, and Alleles
Ch. 6.3 – 6.4

31. Lesson Objectives At the end of this lesson, students will be able to…
Explain how genes are expressed in terms of genotype and phenotype, homozygous, heterozygous
Explain the difference between dominant and recessive alleles in terms of how this affects phenotype

32. Why are chromosomes important?
They carry instructions called genes - The specific set of genes that a chromosome carries is called the genotype
Genes determine the physical appearance and function of an organism – the physical expression of the genotype is called the phenotype.
Traits are physical characteristics expressed in the phenotype (eye color, size, etc)

33. Gregor Mendel Austrian monk – mid 1800s
He worked in the gardens of the monastery paying special attention to the traits of pea plants
At this time no one knew about DNA or how it worked, they could only observe phenotypes

34. Mendel
Flowering plants contain both male and female parts – this means they can self pollinate or cross pollinate

35. Gregor Mendel
Mendel bred thousands of pea plants and recorded every outcome
He noticed that there seemed to be a pattern of traits in his data

36. Pea Traits

37. Gregor Mendel
At the time it was thought that offspring were always an even blend of parent characteristics
Mendel observed that traits seemed to be “either-or” and not a blend at all
This observation allowed him for correctly predict genetic inheritance decades before it could be proven

38. Gregor Mendel
One of the patterns he saw was that each trait seemed to have a common and rare form
The common form showed up about 3 times more often in F2 than the rare trait
In other words, the ratio of common to rare versions of a certain trait was 3:1
Fig 3.4

39. Pea Phenotypes

40. Gregor Mendel
These more commonly seen traits are called dominant
Dominant does NOT mean better or stronger
The less common traits are called recessive
Recessive does NOT mean worse or weaker
Remember: Mendel is in control of breeding, when left to nature, dominant isn’t always more common

41. Discuss: Looking at figure 3.3 on page 168:
Would you say that purple flowers are dominant or recessive? Why?

42. Pea Genotypes
Note that each parent has 2 of the same and each F1 has 1 of each

44. Gregor Mendel
Mendel was well educated, but his success was partly luck
He just happened to make 3 key choices that worked in his favor:
He had control over breeding
Used purebred plants
And observed “either-or” traits

45. Gregor Mendel See pages 168-169
After selectively crossing the plants Mendel observed the presentation of 7 traits (fig 3.4)
His findings would later go on to support the Law of Segregation which says:
Organisms inherit 2 copies of each gene, one from each parent
The organisms then donates one copy of each gene to their own gametes so the 2 copies become separated

46. Homework: Catch up: For tomorrow: 6.1 # 2 6.2 # 4 6.3 # 4
Read 6.4 ***DEFINE: gene, allele, homozygous, heterozygous, dominant, and recessive***
This will be DUE first thing tomorrow

47. Do you have a genetic twin??
At your desk: Fill out your predictions and your own traits
Then: get up and fill in traits for 5 other people and see if you can find a “genetic twin!”
Once you have 5 people sit in your seat

48. Same gene, many versions
Genes are sections of DNA that contain instructions to produce certain traits or necessary cell parts
Since we get half of our DNA from one parent and half from the other, there is a possibility that we will inherit different versions of that gene

49. Same gene, many versions
The version of a gene that we inherit from each parent is called an ALLELE
In peas we talked about dominant and recessive traits, this was caused by dominant and recessive alleles
Yellow = Dominant, Green = Recessive

50. Pea Phenotypes

51. Same gene, many versions
When both parents donate the SAME version of a gene (allele), we say the offspring is HOMOZYGOUS for that particular gene
“Homo” = the same GG
When each parent donates a DIFFERENT allele, we say the offspring is HETEROZYGOUS for that particular gene
“Hetero” = different Gg
See page 170 “Visual Vocab”

52. Genotype and Phenotype
The GENOME is ALL of the genetic material an organism has
The GENOTYPE of an organism is the specific combination of genes it has
The PHENOTYPE is the way that the genotype is physically expressed – in other words, the set of traits or characteristics an organism has

53. Dominant and Recessive
With most genes there is a dominant and recessive allele
Remember, this isn’t talking about better or worse – just which allele will mask the other one
Dominant alleles will overpower recessive alleles so the dominant phenotype shows up
A recessive phenotype will only show up if the alleles are homozygous recessive (see pg. 171 “visual vocab”)

54. Dominant and Recessive
When we are talking about dominant and recessive alleles we use upper and lower case letters to symbolize them
Uppercase is dominant
Lowercase is recessive

55. Practice: Dominant and Recessive
Pretend a mouse’s coat color is determined by an allele on a particular chromosome.
Black hair is dominant (C) and white hair is recessive (c).
What are the possible genotypes for a black mouse?
What are the possible genotypes for a white mouse?

56. Homework Catch up: For tomorrow: 6.1 # 2 6.2 # 4 6.3 # 4
6.4 Definitions
For tomorrow:
Read 6.5 # 5