chromosomes and meiosis unit
DESCRIPTION
Chromosomes and Meiosis Unit. Cell Types. 1) Somatic Cells (aka: body cells) - are diploid (2n) - DNA not passed on. Cell Types. 2) Gametes (aka: sex cells) - ex: ova (egg) and spermatozoa (sperm) - are haploid (1n) - DNA passed on. Egg and Sperm Comparative Size. - PowerPoint PPT PresentationTRANSCRIPT
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Chromosomes and Chromosomes and Meiosis Meiosis
UnitUnit
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Cell TypesCell Types
1) Somatic Cells (aka: body cells)1) Somatic Cells (aka: body cells)
- are diploid (2n)- are diploid (2n)
- DNA not passed on- DNA not passed on
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Cell TypesCell Types
2) Gametes (aka: sex cells)2) Gametes (aka: sex cells)
- ex: ova (egg) and - ex: ova (egg) and spermatozoa (sperm)spermatozoa (sperm)
- are haploid (1n)- are haploid (1n)
- DNA passed on- DNA passed on
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Egg and Sperm Comparative SizeEgg and Sperm Comparative Size
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Diploid vs. HaploidDiploid vs. HaploidDiploid cells have two Diploid cells have two copies of each copies of each chromosome: one copy chromosome: one copy from the mother and from the mother and one from the father.one from the father.
Haploid cells have only Haploid cells have only one copy of each one copy of each chromosomechromosome
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Look at the following Look at the following chromosome numbers of chromosome numbers of these living things.these living things.
Do you notice anything Do you notice anything about the numbers?about the numbers?
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Chromosome Numbers of Various Chromosome Numbers of Various Living ThingsLiving Things
Algae Algae
148148CowCow
6060Dog Dog
7878EarthwormEarthworm
3636
KangarooKangaroo
1212MosquitoMosquito
66PigeonPigeon
8080TigerTiger
3838
ShrimpShrimp
254254DeerDeer
7070TurkeyTurkey
8282Horse Horse
6464
HedgehogHedgehog
9090GiraffeGiraffe
6262CabbageCabbage
1818CarpCarp
104104
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ChromosomesChromosomes
Each species has a Each species has a characteristic number of characteristic number of chromosomeschromosomes
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That fact prevents this from That fact prevents this from happeninghappening
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That fact allows this to happenThat fact allows this to happen
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That fact allows this to happenThat fact allows this to happen
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That fact allows this to happenThat fact allows this to happen
Mule = male donkey and a Mule = male donkey and a female horsefemale horse
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That fact allows this to happenThat fact allows this to happen Liger TigonLiger Tigon
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ChromosomesChromosomes (cont) (cont)
TypesTypes
1) Autosomes1) Autosomes
2) Sex Chromosomes2) Sex Chromosomes
- female = XX- female = XX
male = XYmale = XY
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The sex of some species is The sex of some species is determined by the temperature of determined by the temperature of the environment during incubationthe environment during incubation
(mostly occurs in reptiles) (mostly occurs in reptiles)
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ChromosomesChromosomes (cont) (cont)
Humans have 46 chromosomes Humans have 46 chromosomes (23 pairs)(23 pairs)
- 44 autosomes (22 pairs) and - 44 autosomes (22 pairs) and 2 sex chromosomes (1 pair)2 sex chromosomes (1 pair)
- a diploid # (2n) of 46 and a - a diploid # (2n) of 46 and a haploid # (1n) of 23haploid # (1n) of 23
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Karyotype = picture of an Karyotype = picture of an individual’s chromosomesindividual’s chromosomes
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Homologous Chromosomes vs. Homologous Chromosomes vs. Sister ChromatidsSister Chromatids
Homologous Chromosomes = Homologous Chromosomes = two separate chromosomes, two separate chromosomes, one from mom and one from one from mom and one from daddad
- very similar in size and carry - very similar in size and carry the same genes, but they are the same genes, but they are not copies of one anothernot copies of one another
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Homologous Chromosomes vs. Homologous Chromosomes vs. Sister ChromatidsSister Chromatids (cont)
In contrast, each half of a In contrast, each half of a duplicated chromosome is called a duplicated chromosome is called a chromatidchromatid- together, the two chromatids are - together, the two chromatids are called sister chromatidscalled sister chromatids- thus, sister chromatids refers to - thus, sister chromatids refers to the duplicated chromosome that the duplicated chromosome that remain attached (by the remain attached (by the centromere)centromere)
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Homologous Homologous chromosomes chromosomes (shown (shown duplicated) are duplicated) are two separate two separate chromosomes – chromosomes – one inherited one inherited from the mother from the mother and one from and one from the fatherthe father
Homologous Chromosomes
Sister Chromatids
Sister Chromatids
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Homologous Chromosomes vs. Homologous Chromosomes vs. Sister ChromatidsSister Chromatids (cont)
Homologous chromosomes Homologous chromosomes split in Meiosis Isplit in Meiosis I
Sister chromatids split in Sister chromatids split in Meiosis IIMeiosis II
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MeiosisMeiosis
= a form of nuclear division = a form of nuclear division that divides a diploid cell into that divides a diploid cell into a haploid cella haploid cell
- makes egg and sperm- makes egg and sperm
- 2 rounds of division (Meiosis I - 2 rounds of division (Meiosis I and Meiosis II)and Meiosis II)
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MeiosisMeiosis (cont)
Meiosis I – divides Meiosis I – divides homologous chromosomeshomologous chromosomes
Meiosis II – divides sister Meiosis II – divides sister chromatidschromatids
The overall process The overall process produces haploid cells.produces haploid cells.
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Meiosis IMeiosis I
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Meiosis IIMeiosis II
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GametogenesisGametogenesis
1) spermatogenesis = sperm 1) spermatogenesis = sperm production (4 haploid cells)production (4 haploid cells)
- even distribution- even distribution
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SpermatogenesisSpermatogenesis
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GametogenesisGametogenesis (cont) (cont)
2) oogenesis = egg production 2) oogenesis = egg production (1 haploid cell)(1 haploid cell)
- uneven distribution (polar - uneven distribution (polar bodies created)bodies created)
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OogenesisOogenesis
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Comparing Mitosis and MeiosisComparing Mitosis and MeiosisMitosisMitosis - Produces - Produces
genetically genetically identical cells identical cells
- Results in diploid - Results in diploid cells cells
- Takes place - Takes place throughout an throughout an organism’s life organism’s life
- Involved in asexual - Involved in asexual reproductionreproduction
MeiosisMeiosis
- Produces - Produces genetically unique genetically unique cells cells
- Results in haploid - Results in haploid cells cells
- Takes place only at - Takes place only at certain time in life certain time in life cycle cycle
- Involved in sexual - Involved in sexual reproductionreproduction