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Cell Division. Mitosis and Cell Division. All cells go through a cell cycle composed of cell division portion (mitosis) and "resting period" (interphase). Comparing Mitosis and Meiosis. Observational activity with the person next to you… look at the two processes…..( pages 249 and 273)

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mitosis and cell division
Mitosis and Cell Division
  • All cells go through a cell cycle composed of cell division portion (mitosis) and "resting period" (interphase).
comparing mitosis and meiosis
Comparing Mitosis and Meiosis
  • Observational activity with the person next to you… look at the two processes…..( pages 249 and 273)
  • What do these two processes seem to have in common?
  • Be prepared to share your results with the class!
some questions to ponder
Some questions to ponder
  • 1. How does the number of daughter cells produced from mitosis and meiosis differ?
  • 2. How does the ploidy of the daughter cells produced from mitosis and meiosis differ?
  • 3. Do the daughter cells produced from mitosis contain identical genetic complements?
  • 4. Do any of the daughter cells produced from meiosis contain identical genetic complements?
slide5
5. When do the homologous chromosomes separate during mitosis?
  • 6. When do the homologous chromosomes separate during meiosis?
  • 7. When do sister chromatids separate during mitosis?
  • 8. When do sister chromatids separate during meiosis?
vocabulary section 1
Vocabulary section 1
  • gene,
  • homologous chromosomes,
  • haploid,
  • fertilization,
  • diploid,
  • meiosis,
  • crossing over
slide10
gene
  • A gene is a discrete linear sequence of DNA which corresponds to a trait that can be passed on by that sequence of DNA. In more general terms, one can think of genes as the smallest unit of heredity.
homologous chromosomes1
Homologous chromosomes
  • Example - an organism is 2n = 4.
  • This means the organism has a total of 4 chromosomes 
  • Chromosomes 1 & 2 are homologous chromosomes
  • Chromosomes 3 & 4 are homologous chromosomes
  • Chromosomes 1 & 3 came from the mother
  • Chromosomes 2 & 4 came from the father
haploid or n
Haploid or n
  • A cell with half the number of chromosomes as the normal number is called haploid. This is represented by the letter “n”.
  • Gametes or sex cells are haploid so that when they fuse to form a zygote the correct number or chromosomes is restored!
diploid or 2n
Diploid or 2n
  • Diploid cells have the total number of chromosomes in them. These are somatic cells or body cells. If these were to fuse, the number of chromosomes would be double the correct number!
  • This is why the process of meiosis is needed!
slide19
2 sets of 23 make up the 46 in a human.
  • 1 set from mother 23
  • 1 set from father 23
  • 46
slide23
A quick glance at any karyotype will tell you one of the most important facts about chromosomes:
  • They come in pairs.
  • The members of a pair are the same size and shape, and they have the same banding patterns.
  • In other words, each person actually possesses two copies of chromosome 1, two copies of chromosome 2, and so on.
  • Human cells contain 23 pairs of chromosomes.
vocabulary section 11
Vocabulary section 1:
  • gene,
  • homologous chromosomes,
  • haploid,
  • fertilization,
  • diploid,
  • meiosis,
  • crossing over
meiosis1
Meiosis
  • Meiosis Is a Special Type of Cell Division That Occurs in Sexually Reproducing Organisms
  • Why is this different?
  • Normal body cells have a complete set of chromosomes
  • _ Meiosis reduces the number of chromosomes by half to form reproductive cells.
slide26
If normal body cells from mom and dad fused to form a baby, the fertilized egg would have twice as many chromosomes as it should.
  • Meiosis is sometimes called "reduction division" because it reduces the number of chromosomes to half the normal number
  • so that when fusion of sperm and egg occurs, the offspring will have the correct number.
slide27
Meiosis reduces the chromosome number by half, enabling sexual recombination to occur.
  • Meiosis of diploid cells produces haploid daughter cells, which may function as gametes.
  • Gametes undergo fertilization, restoring the diploid number of chromosomes in the zygote
meiosis is not sexual reproduction
Meiosis is NOT sexual reproduction
  • It does produce cells used in sexual reproduction!
  • Gametes!
sexual or asexual
Sexual or Asexual?
  • Is there an advantage to one or the other as far as helping a population survive?
the role of sexual reproduction in evolution
The Role of Sexual Reproduction in Evolution

Sexual reproduction in a population should decline in frequency relative to asexual reproduction because...

    • Asexual reproduction—No males are needed, all individuals can produce offspring.
    • Sexual reproduction—Only females can produce offspring, therefore fewer are produced.
  • Sexual reproduction may exist because it provides genetic variability that reduces susceptibility of a population to pathogen attack.
purpose
purpose
  • the purpose of meiosis is to produce gametes; the sperm and eggs that have ½ the genetic information of a somatic cell.
  • When the reproductive cells unite in fertilization, the normal diploid number is restored.
meiosis2
Meiosis
  • Interphase I: Identical to Interphase in mitosis.
prophase i
Prophase I:

Chromosomes condense and become visible

Homologous chromosomes come together in pairs to form tetrads in a process called synapsis

Chromatids exchange segments in a process called crossing over

Rearranges genetic information and increases diversity This is Different from mitosis!!!

  • Nuclear envelope breaks down and disappears

Mitotic spindle forms

slide37
Homologous chromosomes contain the matching alleles donated from mother and father. This is also when meiotic recombination, also know as "crossing over" occurs. This process allows for a genetic shuffling of the characteristics of the two parents, creating an almost infinite variety of possible combinations. See the close-up diagram below.
slide38
This is also when meiotic recombination, also know as "crossing over" occurs.
  • This process allows for a genetic shuffling of the characteristics of the two parents, creating an almost infinite variety of possible combinations.
metaphase i
Metaphase I:
  • Instead of all chromosomes pairing up single file along the midline of the cell as in mitosis, homologous chromosome pairs line up next to each other.
      • Chromosome tetrads align at the cell midline
      • Mitotic spindle fibers attach to centromeres
  • This is Different
  • from mitosis!!!
anaphase i
Anaphase I
  • Instead of chromatids splitting at the centromere,
  • homologous chromosome pairs (now shuffled by crossing over) move along the spindle fibers to opposite poles.
    • Anaphase I:
      • Homologous chromosomes separate to opposite poles of the cell
      • Sister chromatids stay together!!!
telophase i
Telophase I
  • The cell pinches and divides, making 2 cells
  • Are the cells still diploid?
telophase i1
Telophase I:
  • Chromosomes arrive at the poles
  • Cytokinesis results in the formation of two haploid cells with duplicated chromosomes
summary of meiosis 1
Summary of Meiosis 1
  • During meiosis I, homologous chromosomes separate.
  • Crossing-over during prophase I results in the exchange of genetic material between homologous chromosomes.
prophase ii
Prophase II:
  • It is visibly obvious that replication has not occurred again.
metaphase ii
Metaphase II:
  • The paired chromosomes line up.
anaphase ii
Anaphase II:
  • The chromatids split at the centromere and migrate along the spindle fibers to opposite poles.
telophase ii
Telophase II:
  • The cells pinch in the center and divide again.
  • The final outcome is four cells,
  • each with half of the genetic material found in the original.
summary of meiosis ii
Summary of Meiosis II
  • During meiosis II, the two chromatids of each chromosome separate.
  • As a result of meiosis, four haploid cells are produced from one diploid cell.
comparing mitosis and meiosis1
Comparing mitosis and meiosis
  • http://www.pbs.org/wgbh/nova/miracle/divi_text.html
slide54
http://www.bing.com/videos/search?q=meiosis&view=detail&mid=A3A49947C08C801B2E98A3A49947C08C801B2E98&first=0&FORM=LKVR15http://www.bing.com/videos/search?q=meiosis&view=detail&mid=A3A49947C08C801B2E98A3A49947C08C801B2E98&first=0&FORM=LKVR15
results
Results
  • In the case of males, each cell becomes a sperm.
  • In the case of females, one cell becomes an egg and the other three become polar bodies which are not used.
meiosis3
Meiosis
  • _ In sexually reproducing eukaryotic organisms, gametes form through the process of spermatogenesis in males and oogenesis in females.
comparing mitosis and meiosis2
Comparing mitosis and meiosis
  • http://www.pbs.org/wgbh/nova/miracle/divi_text.html
comparing mitosis and meiosis3
Comparing Mitosis and Meiosis
  • Observational activity
  • In your groups, use the pictures from your notebook drawings and in the book
  • ( pages 249 and 273) of the phases of mitosis and meiosis. Make a chart that lists the phases and what is different /the same from phase to phase. Be prepared to share your results with the class!
  • Make a Venn diagram of what Mitosis and Meiosis have in common and what differences they have. Goal: 5 in each section
record your reflection scores from chapter 9 add your score how are you doing
Record your reflection scores from chapter 9, add your % score.How are you doing?
  • Remove the directions from the reflections. Keep these in your notebook.
  • Look over the directions for the benchmark on 16.17.
  • This is what you will be tested on next week!
review assignment
Review assignment
  • In groups:
  • 1. Discuss the benchmarks for reflections for section 1 of chapter 10.
  • 2. Make a group list of questions you have about the benchmarks. Write these on the white boards.
slide65
1. SC.912.L.16.16 Describe the process of meiosis, including independent assortment and crossing over.

Explain how reduction division results in the formation of haploid gametes or spores.

2. SC.912.L.15.15 Describe how mutation and genetic recombination increase genetic variation

3. SC.912.L.16.17 Compare and contrast mitosis and meiosis and relate to the processes of sexual and asexual reproduction and their consequences for genetic variation.

slide66
SC.912.L.16.16 Describe the process of meiosis, including independent assortment and crossing over.
  • Explain how reduction division results in the formation of haploid gametes or spores.
  • Meiosis is reduction division! It has 2 phases meiosis 1 which divides the homologues/ makes the cells haploid.
  • Meiosis 2 : which divides the sister chromatids /copies.
figure 13 10 3
Figure 13.10-3

Possibility 2

Possibility 1

Two equally probablearrangements ofchromosomes atmetaphase I

Metaphase II

Daughtercells

Combination 1

Combination 2

Combination 3

Combination 4

slide68
SC.912.L.15.15 Describe how mutation and genetic recombination increase genetic variation.
  • These are just differences !
  • Egg + sperm = a new combination of genes! This is genetic variation!!!!
  • What are two places in the process of meiosis genetic variations can occur?
slide69
SC.912.L.16.17 Compare and contrast mitosis and meiosis and relate to the processes of sexual and asexual reproduction and their consequences for genetic variation.
  • Mitosis is like cloning, offspring are identical to parents.
  • Meiosis: produce gametes that fuse to produce offspring that are different from the parents/ much more chance for genetic variation ( differences)
figure 13 9
Figure 13.9

MITOSIS

MEIOSIS

Parent cell

MEIOSIS I

Chiasma

Prophase

Prophase I

Chromosomeduplication

Chromosomeduplication

Duplicatedchromosome

Homologouschromosome pair

2n 6

Metaphase I

Metaphase

Anaphase I

Telophase I

AnaphaseTelophase

Haploidn 3

Daughter cells ofmeiosis I

MEIOSIS II

2n

2n

Daughter cellsof mitosis

n

n

n

n

Daughter cells of meiosis II

SUMMARY

Mitosis

Property

Meiosis

Occurs during interphase beforemitosis begins

Occurs during interphase before meiosis I begins

DNAreplication

One, including prophase, metaphase,anaphase, and telophase

Two, each including prophase, metaphase, anaphase,and telophase

Number ofdivisions

Occurs during prophase I along with crossing overbetween nonsister chromatids; resulting chiasmatahold pairs together due to sister chromatid cohesion

Synapsis ofhomologouschromosomes

Does not occur

Two, each diploid (2n) and geneticallyidentical to the parent cell

Four, each haploid (n), containing half as manychromosomes as the parent cell; genetically differentfrom the parent cell and from each other

Number of daughter cellsand geneticcomposition

Enables multicellular adult to arise fromzygote; produces cells for growth, repair,and, in some species, asexual reproduction

Produces gametes; reduces number of chromosomesby half and introduces genetic variability among the gametes

Role in the animal body

slide71

SC.912.L.16.17 Compare and contrast mitosis and meiosis and relate to the processes of sexual and asexual reproduction and their consequences for genetic variation. 19 points total

Make a Venn diagram to compare Mitosis and meiosis 5 points per section. Number and name phases when you list things!

Mitosis in common Meiosis

Name 2 places in the process where genetic variation is increased

____________________________________and _______________________________

Which process produces cells for sexual reproduction? _________________________

Which process can be used a method of asexual reproduction?__________________

.

these are from a different book
These are from a different book!
  • asexual reproduction (150)
  • clone (150)
  • sexual reproduction (150)
  • life cycle (152)
  • fertilization (153)
  • sporophyte (154)
  • spore (154)
  • gametophyte
asexual reproduction
Asexual Reproduction
  • _ Asexual reproduction is the formation of offspring from one parent. The offspring are genetically identical to the parent.
sexual reproduction
Sexual reproduction
  • _ Sexual reproduction is the formation of offspring through the union of gametes. The offspring are genetically different from their parents.
slide77
_ A disadvantage to asexual reproduction in a changing environment is the lack of genetic diversity among the offspring.
slide78
_ Sexual reproduction increases variation in the population by making possible genetic recombination.
slide80
_ Eukaryotic organisms can have one of three kinds of sexual life cycles, depending on the type of cell that undergoes meiosis and on when meiosis occurs.
slide84
the diploid (2n) phase in the life cycle that produces spores is called a sporophyte
  • (SPOH ruh fiet)
  • The gametophyte is the haploid (n) phase

that produces gametes by mitosis.

The gametophyte produces gametes

that fuse and give rise to the diploid phase.

some questions to ponder1
Some questions to ponder
  • 1. How does the number of daughter cells produced from mitosis and meiosis differ?
  • 2. How does the ploidy of the daughter cells produced from mitosis and meiosis differ?
  • 3. Do the daughter cells produced from mitosis contain identical genetic complements?
  • 4. Do any of the daughter cells produced from meiosis contain identical genetic complements?
slide87
5. When do the homologous chromosomes separate during mitosis?
  • 6. When do the homologous chromosomes separate during meiosis?
  • 7. When do sister chromatids separate during mitosis?
  • 8. When do sister chromatids separate during meiosis?
answers
answers
  • 1. How does the number of daughter cells produced from mitosis and meiosis differ?
  • When mitosis is complete, there are two daughter cells. When meiosis is complete, there are four.
  • 2. How does the ploidy of the daughter cells produced from mitosis and meiosis differ?
  • Mitosis produces diploid (2n) cells. Meiosis produces haploid (n) cells.
  • 3. Do the daughter cells produced from mitosis contain identical genetic complements?
  • Yes, the purpose of mitosis is to produce two identical cells
  • 4. Do any of the daughter cells produced from meiosis contain identical genetic complements?
  • No, the genetic information swapped between homologous chromosomes during crossing over insures that each daughter cell produced during meiosis will be unique
slide89
5. When do the homologous chromosomes separate during mitosis?
  • Never, they are never joined during mitosis (no tetrads are formed)
  • 6. When do the homologous chromosomes separate during meiosis?
  • Homologs separate during Anaphase I, when the tetrads break
  • 7. When do sister chromatids separate during mitosis?
  • Sister chromatids separate during Anaphase.
  • 8. When do sister chromatids separate during meiosis?
  • Sister chromatids separate during Anaphase II.
advantages of sexual reproduction
Advantages of Sexual reproduction
  • Independent assortment, crossing-over, and random fertilization contribute to produce genetic variation in sexually reproducing organisms.
definitions
definitions:
  • Allele - alternate forms of the same gene
  • Homozygous - having two identical alleles for a given gene
  • Heterozygous - having two different alleles for a given gene
  • Genotype - genetic makeup of an organism
  • Phenotype - the expressed traits of an organism