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Meiosis
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Meiosis
Meiosis
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Chromosomes
Each organism has a certain number of chromosomes:
Human beings = 23 pairs, 46 total
Orangutan = 24 pairs, 48 total
Mosquito = 3 pairs, 6 total Fern = 510 pairs, 1,020 total
Homologous chromosomes: a pair of chromosomes in somatic cells that are similar in size, shape and content. *one is from the female parent *one is from the male parent.
You have 25,000 genes located on only 46 chromosomes!!!!
These pairs have same genes in the same locations... (hair color) but may code for a different version of the gene (blond vs. brown)
size of a chromosomeHuman egg, X & Y, DNA
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Karyotype:a photo of chromosomes arrangedby homologous pairs and size
When are chromosomes visible (in the cell cycle)?
can be sorted into homologous pairs
Karyotypes can tell us sex of organism...The sex chromosome (23rd pair) are referred to as X and Y
Male ______ Female______
by size and shape
Autosomes: chromosomes not involved in determining if male or female.
(the other 22 pair)
Genetic counselors can use a karyotype to check for abnormalities.
*fetal karyotyping
example: Trisomy 21 (Down Syndrome) an individual with 3 copies of chromosome 21
Triple X
XYY syndrome
Klinefelter's Syndrome
Edward's syndrome Trisomy 18
Patau Syndrome Trisomy 13
Turner's Syndrome XO
XXY
XYYXXX
Male or Female? Syndrome?
https://www.youtube.com/watch?v=hNMYV213xu0
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Review:1.What is a karyotype?
2.How many pairs of chromosomes are in a normal human karyotype?
5.What is trisomy 21 in terms of the karyotype in terms of expressed result in individual?
3.What are autosomes?
4.What are sex chromosomes?
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MeiosisProcess of making gametes for sexual reproduction.
* two cell divisions
One diploid somatic cell (46 chromosomes)produces four haploid gametes (23 chromosomes)
2N
N
https://www.youtube.com/watch?v=jjEcHra3484
Mitosis vs. Meiosis
1 division 2 divisions
2 daugher cells 4 daughter cells
identical genes 1/2 genes, variation
somatic cells gametes (egg or sperm
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Draw and write the stages of Meiosis in orderp.144145
play close attention toindependent assortmentcrossing over
p .149Reveiw
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1. How many chromosomes do humans have?
2. What is our diploid number?
3. What is our haploid number?
4. How are chromosomes sorted in a karyotype?
5. What (2) pieces of information can be gained from a karyotype?
6. How many cell divisions occur in meiosis?
7. What happens to the number of chromosomes in meiosis?
8. How many cells result?
9. What type of cells are made in meoisis?
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Fertilization:egg and sperm combine to form a zygote
haploid: diploid:1 full set 2 full sets
23 chromosomes 46 chromosomes
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What is fertilization?
Draw a model and describe it in an organism with 50 chromosomes.
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1. Independent assortment
2. Crossingover
3. Random Fertilization
Meiosis and Genetic Variation * no two individuals are identical..
due to 3 processes:
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1. Independent Assortment the random distribution of homologous chromosomes
Number of different chromosome combinations possible in humans? 223 (8 million)
Occurs during metaphase 1 (meiosis 1)
*p.146 in text
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2. CrossingOver:the exchange of genes on homologous chromosomes
Occurs during Prophase 1 (Meiosis 1)
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What are the 3 process involved that account for the fact that no 2 individuals are alike?
(How do we get variation?)
1.
2.
3.
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1. Independent assortment
2. Crossingover
3. Random Fertilization
Meiosis and Genetic Variation
* no two individuals are identical.. due to:
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3. Random Fertilization
random joining of egg and sperm.
http://www.youtube.com/watch?v=9MnQxiSJZ4Q
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Meiosis and Gamete Formation* Male and Female organisms vary in the structures they produce through Meiosis.
How many cells does Meiosis create? ____
• The cytoplasm divides unequally
• The largest becomes an egg. The other three cells (very small) become polar bodies.
Oogenesis: the process by which gametes (eggs or ovum) are produced in female animals.
(egg or sperm)
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Spermatogenesis: the process by which gametes (sperm) are produced in male animals.
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DIGITAL Genetic Variation PROJECT
Create a labeled diagram for each of the 3 processes that create genetic variation through Meiosis.
• One sentence describing what genetic variation is.• 3 labeled diagrams• 1 sentence explanation for each diagram• use all vocabulary listed below
1. Independent Assortment:Vocab: homologous chromosomes, gametes
2. Crossing over:Vocab: nonsister chromatids, homologous
chromosomes, genes3. Random Fertilization:
Vocab: ovum, sperm, zygote, fertilize (fertilization), haploid, diploid
One in ONENOTE
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• Asexual reproduction a single parent passes copies of all of its genes to each of its offspring no fusion of haploid cells (gametes) result is a clone, an organism that is
genetically identical to its parent.
ex: binary fission, hydra budding
• Sexual reproduction two parents each form reproductive cells that are haploid (n).
• gametes join in a process known as fertilization (egg and sperm fuse to form a zygote)
https://www.youtube.com/watch?v=B7ANli2xfY
http://www.arkive.org/brownhydra/hydraoligactis/video09.html
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• Asexual reproduction The good: many offspring in a short period of time, (without using energy to produce gametes or to find a mate) The bad: However, the DNA of these organisms varies little between individuals.
• Sexual reproductionThe good: quickly makes different combinations of genes among individuals • genetic diversity is the raw material for evolution
Advantages and Disadvantages
http://learn.genetics.utah.edu/content/variation/reproduction/
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mitosis
disadvantage: lack of variation
clone
advantage: provides immeasurable variation
(which powers evolutions)
genetically identical offspring
gametes half the number of chromosomes.
gametes (egg and sperm) join
advantage: no energy needed to produce gametes
or to find a mate.
asexual reproduction sexual reproductionReview • BIO.11.1 I can differentiate between sexual and asexual variation.
fertilization meiosisone parent
two parents
binary fission
zygoteadvantage: many offspring in a short period of time,
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disadvantage: lack of variation
advantage: provides immeasurable variation
(which powers evolutions)
clone an individual genetically identical to its parent
two parents each form gametes that have onehalf the number of chromosomes.
the gametes (egg and sperm) join in a process called fertilization
advantage: many offspring in a short period of time,without using energy to produce gametes
or to find a mate.
one parent passes copies of all of its DNA to each of its offspring
asexual reproduction sexual reproductionReviewCheck • BIO.11.1 I can differentiate between sexual and asexual variation.
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*look at your diagram
1. Independent Assortment the random distribution of homologous chromosomes
Number of different chromosome combinations possible = 223 (8 million)
occurs during meiosis 1 (metaphase 1)