Period 6 only:
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Period 6 only:
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Period 6 only:. * Bats have 72 chromosomes in all of their body cells. * The first cell of the organism is made by joining egg and sperm. How many chromosomes in a bat egg or a sperm cell? Explain. Can cell division by mitosis (duplication of cells) produce egg or sperm? Explain. ?. - PowerPoint PPT Presentation
Transcript of Period 6 only:
Period 6 only:
* Bats have 72 chromosomes in all of their body cells.
* The first cell of the organism is made by joining egg and sperm.
1) How many chromosomes in a bat egg or a sperm cell? Explain.
2) Can cell division by mitosis (duplication of cells) produce egg or sperm? Explain.
46Zygote
Gametes
??
HUMANS!
46Zygote
Gametes
2323
HUMANS!
72Zygote
Gametes
??
BATS!
72Zygote
Gametes
3636
BATS!
2N
Mitosis: 1 Diploid to 2 Diploids:
2N
2NTetraploid
4N
Meiosis: 1 Diploid to 4 Haploids:
2N 4N 1N 1N1N 1N
DNA replication
DNA replication
Draw the following cell:
1) How many chromosomes? 2) How many types of chromosomes (N=?)?3) Is this a diploid or a haploid cell? Explain.
Purpose:Mitosis: Make more identical
diploid cells.
Meiosis: a. Reduce chromosome number by half
b. Create genetic diversity
Mitosis animation
Meiosis Animation
animation
Period 1,2: Drawing – continuedPeriods 4, 5, 6: Drawing - mitosis, meiosis(period 6 – skip the yarn?)
Yarn Kit: Meiosis (finally..)Using the four colors Show the split-split process.What do you get?
Drawing of mitosis and meiosis
Comparing Mitosis and Meiosis
Fill in the handout, comparing mitosis and meiosis + pictures at the bottom.
JOURNAL
A group-class observation1. Make 4 egg/sperm cells from the yarn pieces (Use your drawing for reminder), N=2.2. Draw each ‘egg’ on one quarter of a page, colored. Add to poster.
GENERATING VARIATION
3. Eliminate repeats. How many combinations are possible?4. Repeat procedure with N=3
GENERATING VARIATION:Counting combinations of chromosomes in gametes:2N=4
When N=2 There are 4 possible combinations of gametes
2N=6
When N=3 There are 8 possible combinations of gametes
Calculate number of possible combinations in gametes:Haploid no., N = ?
Calculation No. of com-binations
N=2N=3N=4N=23 (human!)
4816?
2x2= 2x2x2= 2x2x2x2=
22=23=24=
2x2….x2= 223=
? (use calculator)
…. 2x2x2x2x….2=223=________In humans, one male can make:
types of sperm.
In conclusion: Variation amongst eggs/sperm of the same individual is generated by the random segregation of homologous chromosomes in meiosis.
Many flowers can self-pollinate, meaning that both parents are identical.
1. Will their seeds grow into identical plants? Explain.
2. Why are we different from our siblings?
3.What % of our genes did we inherit from each grandparent? Explain.
And this is not the end of it!CROSSING OVER…
The exchange of segments between homologous chromosomes in the beginning of meiosis1.
Meiosis (Lewport)Meiosis with crossing over
Crossing over:
Tokyo_Med Animations
Sources for genetic variation– a summary:
A. Random segregation during meiosis.
B. Crossing overvariation within each parent.random selection of eggs of
sperm during fertilization.C. Different parents.
The Sexual Reproductive Cycle:
When is genetic variation generated?
2N
2N2N
2N1N
1NZygote
GametesOvaries
Testes
Meiosis
Mitosis
Fertilization
2N
2N2N
2N1N
1NM
eiosisMitosis
Fertilization
When is variation produced?
**
Men have XY, Women have XX.Accordingly, which of the two parents determines the gender of the child? Explain.
46xx 46xy
22+x 22+x 22+y 22+x
Normal Male: 46 XYNormal Female: 46 XXKleinfelter Male: 47 XXYTurner Female: 45 X 1. Accordingly, what determines
sex – number of X’s or presence of the Y? Explain.
2. What question(s) do you have in regards to human chromosomes? (no ‘none’)
Quiz
1)Draw the chromosomes in a diploid cell of an organism where N=3.
2) How many combinations of haploid (eggs or sperm) cells are possible if N=2, N=3? Draw the possible combinations.
If N=2:
2N:
