rod shaped structures inside the nucleus of eukaryotic cells made of dna and proteins contain the...
TRANSCRIPT
Rod shaped structures inside the nucleus of Eukaryotic cells
Made of DNA and proteins Contain the genes that make you, you! Shape of the chromosome is
maintained by histones
3 forms of a chromosome› Chromatin – ball of
yarn› Chromatid – half of
an x, sometimes bent
› Chromosome – X Center of X is
called a centromere
Sex Chromosomes › Determine the sex of the organism› Males XY› Females XX› 2 out of 46 in the human cell
Autosomes› All the other chromosomes › 44 out of 46 in the human cell
Chapter 8
Click below to watch the Visual Concept.
Visual Concept
Sex Chromosomes and Autosomes
Section 1 Chromosomes
Also called homologues 2 copies of the
chromosome› One from Mom; One from
Dad Have the same size Have the same shape Have the same
information (genes)
Diploid › Cells that have
chromosomes in pairs
› Symbol 2n› Somatic cells or
body cells are like this
› Humans diploid number is 46.
Haploid› Cells that do not
have chromosomes in pairs
› Symbol 1n› Gametes are like
this Sex cells Sperm and egg cells
› Humans haploid number is 23.
Section 2 Cell DivisionChapter 8
Cell Division in Prokaryotes, continued
• Binary fission is the process of cell division in prokaryotes.
Asexual Reproduction› Production of
offspring from one parent
› Mitosis
Sexual Reproduction› Production of
offspring from 2 parents
› Meiosis
How do little elephants grow up to be BIG elephants?
The process of asexual reproduction begins
after a sperm fertilizes an egg.
Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun.
Cell that reproduce by asexual reproduction reproduce constantly.
Animated Mitosis Cyclehttp://www.cellsalive.com/mitosis.htm
• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase & Cytokinesis
• 3 phases• G1 – cell is growing• S – DNA is being copied• G2 – cell is preparing for mitosis
CELL MEMBRANENucleus
Cytoplasm
Nuclear MembraneAnd nucleolus are visible
CHROMATIN!
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• Mitosis begins (cell begins to divide)• Chromosomes are visible• Centrioles (or poles) appear and begin to
move to opposite end of the cell. • Spindle fibers form between the poles.
CentriolesSister chromatids
Spindle fibers
Nuclear membrane & nucleolus disappear by end of prophase
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Spindle fibers
Centrioles
• Chromosomes attach to the spindle fibers at the centromere
Centrioles
Spindle fibers
CHROMOSOME
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell.
Centrioles
Spindle fibers
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• Two new nuclei form. • Chromosomes appear as chromatin
(threads rather than rods).• Mitosis ends.
NucleiNuclei
Chromatin
Nuclear membrane & nucleolus are visible by end of telophase
Overlaps with cytokinesis!
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• Division of the cytoplasm• Cell membrane moves inward to create two daughter cells –
each with its own nucleus with identical chromosomes.• Animal cells – form a cleavage furrow• Plant cells – form a cell plate, which becomes the cell wall.
Animal Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Plant Mitosis -- ReviewInterphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
IInterphasePProphaseMMetaphaseAAnaphaseTTelophaseCCytokinesis
IPMATIPMATCC
II PPrayray MMore ore AAtt TThe he CChurchhurch
32
http://www.cellsalive.com/mitosis.htm
Section 2 Cell DivisionChapter 8
Control of Cell Division
• Cell division in eukaryotes is controlled by many proteins.
• Control occurs at three main checkpoints.
1. G1 checkpoint – check to see whether the cell is healthy and is large enough to divide
2. G2 checkpoint – check to make sure DNA is copied correctly
3. Mitosis checkpoint – if cell divided correctly, then signals are made to exit mitosis
Chapter 8
Click below to watch the Visual Concept.
Visual Concept
Control of the Cell Cycle
Section 2 Cell Division
Section 2 Cell DivisionChapter 8
Control of Cell Division, continued
• When Control is Lost: Cancer– Cancer is uncontrolled growth of cells– Cancer may result if cells do not respond to
control mechanisms.– Can be caused by mutations in DNA
Section 3 MeiosisChapter 8
Formation of Haploid Cells
• Meiosis is a process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell. • Start with 46 and end with 23
• Meiosis leads to four haploid cells (gametes) rather than two diploid cells as in mitosis.
• Done by germ cells• Meiosis produces haploid gametes.• Is considered sexual reproduction• Creates genetic diversity• Two divisions
Section 3 MeiosisChapter 8
Meiosis I
• Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I.
• Crossing-over, which is when portions of homologous chromosomes exchange genetics material, occurs during prophase I and results in genetic recombination.
Homologous chromosomes (paired chromosomes) become visible
Nuclear membrane and nucleolus disappear
Spindle fiber starts to appear
Crossing over occurs – portions of the chromatid break off and attach to other homologous chromosome
Chapter 8
Click below to watch the Visual Concept.
Visual Concept
Tetrads and Crossing-over of Genetic Material
Section 3 Meiosis
Homologous chromosomes (tetrads) line up at the equator and connect to spindle fibers at their centromeres
Homologous chromosomes split and individual chromosomes move to poles
They assort independently of one another- independent assortment
There are 2 new cells at this point
Each new cell has half the number of chromosomes as the parent germ cell
So they are now haploid
Has prophase II, metaphase II, anaphase II and telophase II
Exactly like mitosis Four new haploid cells result
› Four gametes› Depends on whether it is an animal or a
plant cell
Chapter 8Section 3 Meiosis
Spermatogenesis› Making of sperm
cells› Meiosis will result
in 4 mature sperm cells or spermatozoa
Oogenesis› Making of mature
egg cells, or ova› Meiosis will result
in 1 mature egg cell and 3 polar bodies that die