between cell divisions dna is not tightly coiled into chromosomes-called chromatin regions uncoil...
TRANSCRIPT
Between cell divisions DNA is not tightly coiled into chromosomes-called chromatin
Regions uncoil to be read to direct cell’s activities
Prokaryotes have only 1 chromosome attached to the inside of the cell membrane, still compact to fit in cell but in a loop
When a eukaryotic cell prepares to divide, the DNA and the proteins associated with the DNA coil into a structure called a chromosome
Histones-aid in tight packing of DNA and help maintain the shape of the chromosome
Nonhistone proteins are involved in controlling the activity of specific regions of the DNA
The 2 exact copies of DNA that make up each chromosome are called chromatids
The 2 chromatids of a chromosome are attached at the centromere
The chromatids separate during cell division and are placed into each new cell
Each new cell will have the same genetic information as the original cell
Each species has a characteristic number of chromosomes
Sex chromosomes determine the sex of an individual –XY
Autosomes are all other chromosomesChromosomes come in pairs – one
member from each parentChromosome pairs carry genes for the
same traits Chromosome number (n) tells how
many of each type of chromosome is present in a cell; 2n is diploid
Sperm and egg cells are haploid (1n)-have only ½ the number of chromosomes of diploid cells-why?
Karyotype-a picture of the condensed chromosomes of an individual
Three reasons why cells reproduce by asexual reproduction:
1. Growth 2. Repair 3. Replacement
Cell Division
You make about 2 trillion new cells per day!
• Mitosis-eukaryotic nuclear division-leads to the equal distribution of DNA to 2 new nuclei of daughter cells
• Prokaryotic cells reproduce asexually (only 1 parent) by an entirely different mechanism called binary fission
G1 (Growth 1)G1 (Growth 1) –cell carries out routine functions
S (Synthesis)S (Synthesis) - DNA copied, each chromosome is 2 chromatids attached at the centromere
G2 (Growth 2)G2 (Growth 2) - cell prepares for division, microtubules rearranged
MitosisMitosis – nucleus divided into 2 nuclei
CytokinesisCytokinesis – cytoplasm divides
G0 phase-cell does not copy DNA or prepare to divide
InterphaseProphaseMetaphaseAnaphaseTelophase &
Cytokinesis
• Chromosome # doubles• Chromosomes appear as threadlike coils (chromatin)
Animal Cell Plant Cell
• Mitosis (cell begins to divide)DNA tightens into chromosomes, nuclear membrane breaks down and disappears
• Centrosomes-dark spots that appear next to the nucleus and begin to move to opposite end of the cell-if an animal-then has a pair of centrioles
• Spindle fibers made of microtubules, form between the poles-mitotic spindle-to equally divide the chromatids
Kinetochore fibers-attach to centromeres-extend to the centrosomes
Polar fibers-extend across cell from pole to pole, do not attach to chromosomes
Animal Cell Plant Cell
Kinetochore fibers move chromosomes to the center of the cell
Animal Cell Plant Cell
Chromatids separate and begin to move to opposite ends of the cell.
Animal CellPlant Cell
• Two new nuclei form • Chromosomes appear as chromatin (threads rather than rods)
• Mitosis ends
Animal Cell Plant Cell
Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
