dna terminology…. the cell cycle…. mitosis and meiosis…
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DNA Terminology…. DNA Terminology…. The Cell Cycle….The Cell Cycle….Mitosis and Meiosis…..Mitosis and Meiosis…..
I. ChromosomesI. ChromosomesA. DNA wrapped A. DNA wrapped
around proteins around proteins (histones) is a (histones) is a nucleosomenucleosome
B. Uncoiled, B. Uncoiled, threadlike DNA is threadlike DNA is ChromatinChromatin
(non-dividing cell)(non-dividing cell)
C. DNA called a C. DNA called a chromosome chromosome in dividing in dividing
cells; cells; short, fat rodsshort, fat rods
D.D.Half of a doubled Chromosome Half of a doubled Chromosome = a Chromatid= a Chromatid
1.Contains two identical parts
2. Attach at a point called the Centromere
E. Homologous ChromosomesE. Homologous Chromosomes
1.1. Occurs in pairs; same size and Occurs in pairs; same size and shapeshape
2.2. Structurally different from Structurally different from
all other pairsall other pairs
3. Have the 3. Have the
same gene locationssame gene locations
centromerecentromere
chromatidchromatid
F. GeneF. Gene
1. Distinct unit on a 1. Distinct unit on a chromosomeschromosomes
2. Sequence of 2. Sequence of nucleotidesnucleotides
Eye Color
II. “N” Number = II. “N” Number = The number of The number of chromosomes a cell haschromosomes a cell has
A.A. Diploid (2N)Diploid (2N)1.1. Each species has a Each species has a
characteristic number of characteristic number of chromosomeschromosomes
2.2. Cells with both Cells with both chromosomes of every pair chromosomes of every pair called somatic or body cellscalled somatic or body cells
a)a) 2N for humans = 46 2N for humans = 46 b)b) Ex: Crayfish (200)Ex: Crayfish (200) fruit flies (4)fruit flies (4)
Common Common NameName
Genus and Genus and SpeciesSpecies Diploid NumberDiploid Number
BuffaloBuffalo Bison bisonBison bison 6060
CatCat Felis catusFelis catus 3838
CattleCattle Bos taurus, B. Bos taurus, B. indicusindicus 6060
DogDog Canis familiarisCanis familiaris 7878
DonkeyDonkey E. asinusE. asinus 6262
GoatGoat Capra hircusCapra hircus 6060
HorseHorse Equus caballusEquus caballus 6464
HumanHuman Homo sapiensHomo sapiens 4646
PigPig Sus scrofaSus scrofa 3838
SheepSheep Ovis ariesOvis aries 5454
B.B. Haploid (1N)Haploid (1N)
1.1. Cell with 1 Cell with 1 chromosome of each chromosome of each pairpair
2.2. Sex cell (sperm or Sex cell (sperm or egg)-Gametesegg)-Gametes
III. Asexual and Sexual ReproductionIII. Asexual and Sexual ReproductionA. Mitosis is AsexualA. Mitosis is Asexual
1.1. Functions includeFunctions include
a)a) Unicellular Organism = Unicellular Organism = ReproductionReproduction
b) Multi-cellular Organismsb) Multi-cellular Organisms
1)1) Growth and development from Growth and development from eggegg
2)2) Replacement of dead or Replacement of dead or damaged cellsdamaged cells
c) Passes along the genome (total c) Passes along the genome (total DNA per species)DNA per species)
2.2. Each daughter cell is clone of Each daughter cell is clone of parent.parent.
B.B. Meiosis is SexualMeiosis is Sexual
1.1. Mixes DNAMixes DNA
2.2. Produces Produces ½½ the the number of the number of the chromosomes of chromosomes of the parentsthe parents
3.3. Cells involved in Cells involved in sexual sexual reproduction reproduction
are sperm and are sperm and
eggs (gametes)eggs (gametes)
IV. Cell DivisionIV. Cell DivisionA.A.Prokaryotes: Called Binary FissionProkaryotes: Called Binary FissionB.B.Eukaryotes: Use the Cell CycleEukaryotes: Use the Cell Cycle
1.1.InterphaseInterphase2.2.MitosisMitosis3.3.CytokinesisCytokinesis
V. Cell CycleV. Cell Cycle
= = sequence of growth sequence of growth and division in the life of and division in the life of a cella cell
G1
(growth;Gap 1)
S=Synthesis
G2=Gap 2
1 hr.Cytokinesis
Mitosis
•Rapid cell growth
•Cell doubles in size
•Enzymes + organelles double in number
•Growth
•DNA makes a copy of itself
11 hrs.
7 hrs.•Rapid Growth
•Final preparation for cell division
3 hrs.
Interphase
Cell Cycle =Cell Cycle =Interphase = period of cell growth and
duplication of the DNA
GG11 + S + G + S + G22
Mitosis = division of the cell’s nucleus in which the chromosomes in the parent cell divides into 2 identical sets
Cytokinesis Cytokinesis = cytoplasm divides in 2 = cytoplasm divides in 2 daughter cellsdaughter cells
VI. Stages of MitosisVI. Stages of MitosisProphaseProphase
a) Early Prophasea) Early Prophase
1)1)Chromatin coils to chromosomesChromatin coils to chromosomes
2)2)Nucleolus & nuclear membrane Nucleolus & nuclear membrane break down & disappearbreak down & disappear
3)3)Centrioles move to poles (animal Centrioles move to poles (animal cells only).cells only).
b)b) Middle ProphaseMiddle Prophase
1)1) Spindle fibers Spindle fibers (microtubules) appear(microtubules) appear
2)2) Polar – centriole to Polar – centriole to
centriolecentriole
3)3) Kinetochore – Kinetochore – centromere to centriolecentromere to centriole
c)c) Late ProphaseLate Prophase
1)1)Aster appear Aster appear
(centriole and fibers)(centriole and fibers)
2) Chromosomes 2) Chromosomes
position is randomposition is random
MetaphaseMetaphase
a)a) Kinetochore fibers Kinetochore fibers move chromosomesmove chromosomes
b)b) Chromosomes line up Chromosomes line up along equatoralong equator
Anaphase Anaphase
a)a) Centromere splitsCentromere splits
b)b) Sister chromatids Sister chromatids pulled to opposite pulled to opposite endsends
TelophaseTelophase
a)a) Identical chromatids at Identical chromatids at opposite endopposite end
b)b) Chromatids unwind & Chromatids unwind & elongate to chromatinelongate to chromatin
c)c) Centrioles & spindle Centrioles & spindle disappeardisappear
d)d) Nucleolus & nuclear Nucleolus & nuclear membrane reappearmembrane reappear
1.Prophase
2.Metaphase3.Anaphase
4.Telophase
C.C. CytokinesisCytokinesis1.1. Animal cells form cleavage Animal cells form cleavage
furrowsfurrows2.2. Plant cells form a cell platePlant cells form a cell plate
VII. Reproduction and MeiosisVII. Reproduction and Meiosis
A.A. MeiosisMeiosis in males in males ♂♂
1. Part of 1. Part of spermatogenesisspermatogenesis
2. Occurs in the 2. Occurs in the testestestes
3. Always results in 3. Always results in four sperm cellsfour sperm cells
B.B. Meiosis in females Meiosis in females ♀♀
1.1. Part of oogenesisPart of oogenesis
2.2. Occurs in the ovariesOccurs in the ovaries
3.3. One cell receives One cell receives most of the cytoplasm; most of the cytoplasm; the other 3 cells are the other 3 cells are polar bodiespolar bodies
4.4. Results in mature egg Results in mature egg
( with 23 chromosomes)( with 23 chromosomes)
VIII. Significance of MeiosisVIII. Significance of Meiosis
A.A. Produces genetic variationProduces genetic variation
B.B. Without meiosis, Without meiosis, chromosome numbers would chromosome numbers would continually increasecontinually increase
((teenage mutant Ninja turtles)teenage mutant Ninja turtles)
Common Common NameName
Genus and Genus and SpeciesSpecies
Diploid Diploid NumberNumber
BuffaloBuffalo Bison bisonBison bison 6060
CatCat Felis catusFelis catus 3838
CattleCattle Bos taurus, B. Bos taurus, B. indicusindicus 6060
DogDog Canis familiarisCanis familiaris 7878
DonkeyDonkey E. asinusE. asinus 6262
GoatGoat Capra hircusCapra hircus 6060
HorseHorse Equus caballusEquus caballus 6464
HumanHuman Homo sapiensHomo sapiens 4646
PigPig Sus scrofaSus scrofa 3838
SheepSheep Ovis ariesOvis aries 5454
IX. Review “N” NumberIX. Review “N” NumberMitosis => results in 2N Meiosis => results in 1NMitosis => results in 2N Meiosis => results in 1N
animals animals (1N)(1N) plants (1N)plants (1N)
egg and sperm egg and sperm spores and seeds spores and seeds
(gametes)(gametes)
fusefuse
(2N zygote)(2N zygote)
**♂♂ - sperm all viable after spermatogenesis - sperm all viable after spermatogenesis
**♀♀ - after oogenesis, 1 egg(ootid) and 3 polar - after oogenesis, 1 egg(ootid) and 3 polar bodies (no cytoplasm, just DNA)bodies (no cytoplasm, just DNA)
X. Steps of Meiosis X. Steps of Meiosis (2 Separate Divisions)(2 Separate Divisions)
Meiosis vs MitosisMeiosis vs Mitosis
Meiosis I (starts with 2N)Meiosis I (starts with 2N)Prophase IProphase I Chromatin shortens and coils to chromosomesChromatin shortens and coils to chromosomes Spindle appearsSpindle appears Nucleolus and nuclear membrane disappearNucleolus and nuclear membrane disappear Unique step:Unique step:
– Chromosomes line up next to their homologs Chromosomes line up next to their homologs (called (called synapsissynapsis))
– Homolog pairs twist tightly to form a Homolog pairs twist tightly to form a tetrad tetrad – (4 chromatids that make up two doubled (4 chromatids that make up two doubled
chromosomes)chromosomes)– Crossing over can occur; exchange of DNA Crossing over can occur; exchange of DNA
between homologs and/or 2 sister between homologs and/or 2 sister chromatidschromatids
Tetrad FormationTetrad Formation
Tetrad FormationTetrad Formation
Meiosis IMeiosis IMetaphase IMetaphase I Tetrads move to the equator; homolog Tetrads move to the equator; homolog
pairs stay togetherpairs stay together
Anaphase IAnaphase I Homologous pairs separate and move Homologous pairs separate and move
to each pole ( one chromosome of to each pole ( one chromosome of each pair pulled to pole)each pair pulled to pole)
2 chromatids still joined at centromere2 chromatids still joined at centromere
Meiosis IMeiosis I
Telophase ITelophase I Cytoplasm divides forming 2 Cytoplasm divides forming 2
daughter cellsdaughter cells
Meiosis IIMeiosis II (chromosomes do not (chromosomes do not double; ends with 4 (1n) cellsdouble; ends with 4 (1n) cells
Prophase IIProphase II New spindle formsNew spindle forms Nuclear membrane and nucleolus Nuclear membrane and nucleolus
break apartbreak apart Chromatin shortens and becomes Chromatin shortens and becomes
visible as sister chromatids visible as sister chromatids
Metaphase IIMetaphase II Sister chromatids move to the equatorSister chromatids move to the equator
Meiosis IIMeiosis II
Anapahse IIAnapahse II Centromere divides; sister Centromere divides; sister
chromatids move to opposite poleschromatids move to opposite poles
Telophase IITelophase II Nuclear membrane reforms; Spindle Nuclear membrane reforms; Spindle
disappearsdisappears Cytokinesis occursCytokinesis occurs 4 daughter cells from one parent4 daughter cells from one parent
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