period 6 only:
DESCRIPTION
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 PresentationTRANSCRIPT
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Period 6 only:
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* 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.
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46Zygote
Gametes
??
HUMANS!
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46Zygote
Gametes
2323
HUMANS!
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72Zygote
Gametes
??
BATS!
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72Zygote
Gametes
3636
BATS!
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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
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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.
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Purpose:Mitosis: Make more identical
diploid cells.
Meiosis: a. Reduce chromosome number by half
b. Create genetic diversity
Mitosis animation
Meiosis Animation
animation
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Period 1,2: Drawing – continuedPeriods 4, 5, 6: Drawing - mitosis, meiosis(period 6 – skip the yarn?)
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Yarn Kit: Meiosis (finally..)Using the four colors Show the split-split process.What do you get?
Drawing of mitosis and meiosis
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Comparing Mitosis and Meiosis
Fill in the handout, comparing mitosis and meiosis + pictures at the bottom.
JOURNAL
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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
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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
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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)
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…. 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.
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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.
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And this is not the end of it!CROSSING OVER…
The exchange of segments between homologous chromosomes in the beginning of meiosis1.
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Meiosis (Lewport)Meiosis with crossing over
Crossing over:
Tokyo_Med Animations
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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.
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The Sexual Reproductive Cycle:
When is genetic variation generated?
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2N
2N2N
2N1N
1NZygote
GametesOvaries
Testes
Meiosis
Mitosis
Fertilization
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2N
2N2N
2N1N
1NM
eiosisMitosis
Fertilization
When is variation produced?
**
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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
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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’)
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Quiz
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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: