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Cell Reproduction. Homework!. www.cellsalive.com Complete the mitosis and meiosis sheets. Cells Division Introductory Video. The Chromosome. During cell division the cell’s DNA is coiled compactly into a CHROMOSOME Each chromosome is a single DNA molecule

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homework
Homework!
  • www.cellsalive.com
  • Complete the mitosis and meiosis sheets
the chromosome
The Chromosome
  • During cell division the cell’s DNA is coiled compactly into a CHROMOSOME
  • Each chromosome is a single DNA molecule
  • The DNA wraps tightly around a protein called HISTONE (helps maintain the chromosome’s shape)
breaking down the definitions
Breaking Down the Definitions
  • Chromosome
  • Histone
  • Chromatid
  • Centromere
  • Chromatin
  • Sex chromosome
  • Autosome
  • Homologous chromosome
  • Karyotype
  • Diploid
  • Haploid
  • Binary fission
  • Mitosis
  • Asexual reproduction
  • Meiosis
  • Gamete
  • Interphase
  • Cytokinesis
  • Prophase
  • Spindle fiber
  • Metaphase
  • Anaphase
  • Telophase
  • Cell plate
  • Synapsis
  • Tetrad
  • Crossing over
  • genetic recombination
  • Independent assortment
  • Sexual reproduction
anatomy of a chromosome
Anatomy of a Chromosome
  • Each half of a chromosome is called a CHROMATID
  • Chromatids form as the DNA copies itself before cell division
  • The 2 Chromatids are attached at a point called a CENTROMERE
  • CHROMATIN=less tightly areas of DNA between cell divisions
chromosome numbers
Chromosome Numbers
  • Every species has a certain number of chromosomes in each cell.
  • Animal chromosomes are either:
    • Sex Chromosomes—will determine the gender of an organism (X and Y)
    • Autosomes—all of the other chromosomes
  • Cells with 2 sets of Chromosomes are DIPLOID
  • Cells with one set of chromosomes are HAPLOID (sex cells…half the number of chromosomes)
chromosomes clip
Chromosomes Clip
  • How many chromosomes does a potato have?
  • How many chromosomes do Ferns have?
  • After the video…in your own words why do different organisms have different numbers of chromosomes??
cell division aka cell reproduction in prokaryotes
Cell Division (aka Cell Reproduction) in Prokaryotes
  • Most prokaryotes reproduce by BINARY FISSION
  • 2 identical cells are produced from one cell
  • Draw this
cell division eukaryotes
Cell Division Eukaryotes
  • Two types of Cell Division (Reproduction) in Eukaryotes!
  • Mitosis=new cells with identical genetic material
  • Meiosis=reduces the number of chromosomes by half for the purpose of eventual reproduction
the cell cycle
The Cell Cycle
  • The CELL CYCLE is the repeating events of the life of a cell.
  • Interphase is the period between cell divisions
slide14

Three reasons why cells reproduce by asexual reproduction or MITOSIS: 1. Growth 2. Repair 3. Replacement

slide15

Mitosis Cycle

  • Interphase
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase & Cytokinesis
interphase occurs before mitosis begins
Interphaseoccurs before mitosis begins
  • Chromosomes are copied (# doubles)
  • Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy(sister chromosome) change to sister chromatids at end of this phase

CELL MEMBRANE

Nucleus

Cytoplasm

interphase
Interphase

Plant Cell

Animal Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

prophase 1 st step in mitosis
Prophase 1st step in Mitosis
  • Mitosis begins (cell begins to divide)
  • Centrioles (or poles) appear and begin to move to opposite end of the cell.
  • Spindlefibers form between the poles.

Centrioles

Sister chromatids

Spindle fibers

prophase
Prophase

Plant Cell

Animal Cell

Spindle fibers

Centrioles

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

metaphase 2 nd step in mitosis
Metaphase 2nd step in Mitosis
  • Chromatids(or pairs of chromosomes) attach to the spindle fibers.

Centrioles

Spindle fibers

metaphase
Metaphase

Plant Cell

Animal Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

anaphase 3 rd step in mitosis
Anaphase 3rdstep in Mitosis
  • Chromatids(or pairs of chromosomes) separate and begin to move to opposite ends of the cell.

Centrioles

Spindle fibers

anaphase
Anaphase

Plant Cell

Animal Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

telophase 4th s tep in mitosis
Telophase4th step in Mitosis
  • Two new nucleiform.
  • Chromosomes appear as chromatin (threadsrather than rods).
  • Mitosisends.

Nuclei

Nuclei

Chromatin

telophase
Telophase

Plant Cell

Animal Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

cytokinesis occurs after mitosis
Cytokinesisoccurs after mitosis
  • Cell membrane moves inward to create two daughter cells – each with its own nucleuswith identical chromosomes.
remember

IPMATC

REMEMBER!
  • Interphase
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
  • Cytokinesis

IP___M___ A___T___ C______

meiosis key differences from mitosis
Meiosis – key differences from mitosis
  • Meiosis reduces the number of chromosomes by half.
  • Daughter cellsdiffer from parent, and each other.
  • Meiosis involves two divisions, Mitosis only one.
  • Meiosis I involves:
    • Synapsis – homologous chromosomes pair up. Chiasmata form (crossing over of non-sister chromatids).
    • In Metaphase I, homologous pairs line up at metaphase plate.
    • In Anaphase I, sister chromatids do NOT separate.
    • Overall, separation of homologous pairs of chromosomes, rather than sister chromatids of individual chromosome.

Meiosis KM

meiosis i four phases
Meiosis I (four phases)
  • Cell division that reduces the chromosome number by one-half.
  • four phases:

a. prophase I

b. metaphase I

c. anaphase I

d. telophase I

meiosis
Meiosis
  • The form of cell divisionby which gametes (sperm or egg cells), with half the number of chromosomes,are produced.
  • Diploid (2n)  haploid (n) n=# of chromosomes
  • Meiosis is sexual reproduction.
  • Two divisions (meiosis I and meiosis II).
meiosis1
Meiosis
  • Sex cells divide to produce gametes(sperm or egg).
  • Gametes have half the # of chromosomes.
  • Occurs only in gonads (testes or ovaries).

Male: spermatogenesis

Female: oogenesis

  • Meiosis is similar to mitosis with some chromosomal differences.
slide46

Sex ChromosomesThe Sex Chromosomes code for the sex of the offspring.** If the offspring has two “X” chromosomes it will be a female. ** If the offspring has one “X” chromosome and one “Y” chromosome it will be a male.

In Humans the “Sex Chromosomes” are the 23rd set

XX chromosome - female

XY chromosome - male

slide47

Y chromosome

X chromosome

Boy or Girl? The Y Chromosome “Decides”

interphase i
Interphase I
  • Similar to mitosis interphase.
  • Chromosomes replicate (S phase).
  • Each duplicated chromosome consist of two identical sister chromatids attached at their centromeres.
  • Centriole pairs also replicate.
interphase i1
Interphase I
  • Nucleus and nucleolus visible.

chromatin

nuclear membrane

cell membrane

nucleolus

prophase i
Prophase I
  • Longest and most complex phase (90%).
  • Chromosomes condense.
  • Synapsis occurs: homologous chromosomes come together to form a tetrad.
  • Tetrad is two chromosomes or four chromatids (sister and nonsister chromatids).
prophase i synapsis

Homologous chromosomes

sister chromatids

sister chromatids

Tetrad

Prophase I - Synapsis
prophase i1

spindle fiber

centrioles

aster

fibers

Prophase I
crossing over
Crossing Over
  • Crossing over (variation) may occur between nonsisterchromatids
  • Crossing over: segments of nonsisterchromatids break and reattach to the other chromatid.
crossing over variation

Tetrad

nonsister chromatids

chiasmata: site of crossing over

Crossing Over - variation

variation

slide55

Another Way Meiosis Makes Lots of Different Sex Cells – Crossing-Over

Crossing-over multiplies the already huge number of different gamete types produced by independent assortment.

metaphase i
Metaphase I
  • Shortest phase
  • Tetrads align on the metaphase plate.
  • INDEPENDENT ASSORTMENT OCCURS:

1. The random separation of the homologous chromosomes---this results in GENETIC VARIATION

homologous chromosomes
Homologous Chromosomes
  • Pair of chromosomes (maternal and paternal) that are similar in shape and size.
  • Homologous pairs (tetrads) carry genes controlling the same inherited traits.
  • Each locus(position of a gene) is in the same position on homologues.
  • Humans have 23 pairs of homologous chromosomes.

a. 22 pairs of autosomes

b. 01 pair of sex chromosomes

homologous chromosomes1

eye color

locus

eye color

locus

hair color

locus

hair color

locus

Paternal

Maternal

Homologous Chromosomes
metaphase i1

OR

metaphase plate

metaphase plate

Metaphase I
anaphase i
Anaphase I
  • Homologous chromosomes separate and move towards the poles.
  • Sister chromatids remain attached at their centromeres.
telophase i
Telophase I
  • Each pole now has haploid set of chromosomes.
  • Cytokinesis occurs and two haploid daughter cells are formed.
meiosis ii
Meiosis II
  • No interphase II

(or very short - no more DNA replication)

  • Remember: Meiosis II is similar to mitosis
prophase ii
Prophase II
  • same as prophase in mitosis
metaphase ii

metaphase plate

metaphase plate

Metaphase II
  • same as metaphase in mitosis
anaphase ii
Anaphase II
  • same as anaphase in mitosis
  • sister chromatids separate
telophase ii
Telophase II
  • Same as telophase in mitosis.
  • Nuclei form.
  • Cytokinesis occurs.
  • Remember: four haploid daughter cells produced.

gametes = sperm or egg

meiosis2

n=2

sex cell

sperm

n=2

n=2

2n=4

haploid (n)

n=2

n=2

diploid (2n)

n=2

meiosis I

meiosis II

Meiosis
meiosis mouse
Meiosis – mouse

Parent cell

1st division

2nd division

4 gametes