BIOLOGY cell reproduction, chromosomes, meiosis, meitosis
Change in size
Change in form
Threadlike structures in a cell that contain genetic info that is passed on from one generation of cells to the next
Where are chromosomes located
How many chromosomes does the human body have
46 or 23 pairs (half from each parent)
Normal body cells
Reproductive cells (sperm and egg)
Genetic material that makes up chromosomes
What is chromatin made of
DNA and proteins
Structure of chromatin
DNA is super coiled into a very compact structure during cell division
Proteins that help maintain shape of chromosomes and aods in tight packaging of DNA
Don't participate in the packing of DNA. Involved in controlling activities of DNA.
During cellular division chromatin condenses or coils to form rod like chromosomes
DNA double helix
Begins to coil and wrap tightly around histones to form nucleosomes.
DNA which is tightly wrapped around histones
Large coils of nucleosome coils which make up chromosomes
Half of a chromosome
Comstricted area of each chromatid. Helps hold two chromatids together. Aids in movement of chromosomes during cell division
Pair of chromosomes from different gametes (parents) with genes for the same kinds of characteristics on each
Species number of chromosomes in each cell. Does not indicate species complexity.
Bacterial DNA. Simpler. Usually only one chromosome. Consists of a circular DNA molecule and associated proteins.
Chromosomes that determine sex of an organism. May carry genes for other characteristics.
All of the other Chromosomes in an organism
How many autosomes does a human have
Photomicrograph of the chromosomes in r dividing cell
Every cell of an organism produced by sexual reproduction has two copies of each autosome. One from each parent.
Where do homologous chromosomes occur
Meiosis diploid cells
Each duplicated Chromosome is made up of two halves. Each half is a sister chromatid
When are sister chromatids formed
When DNA is copied during interphase
Three chromosomes instead of two
Cells having two sets of chromosomes. Have both chromosomes from each homologous pair.
What cells are diploid
All normal human cells except reproductive cells are 2n
Contain only one set of chromosomes. Have only half the number of chromosomes that are present in diploid cells.
What cells are haploid
Sperm and egg cells. 1n
Whena sperm cell and an egg cell combine to create the first cell of a new organism and it becomes 2n.
Division of prokaryotic cells into two different offspring cells
Form of asexual reproduction
Cell division in eukaryotes
Mitosis and cytokinesis
The cell cycle
Repeating set of events that make up the life cycle of a cell from cytokinesis to cytokinesis
Cell cycle steps
One stage of the cell cycle. Includes both mitosis and cytokinesis
Time between cell divisions. G1 phase and S phase.
G one phase
DNA is copied
G two phase
Growth and preparation for cell division
G zero phase
Nerve cells exit cell cycle
Division of the nucleus (PMAT)
Shortening and tight coiling of DNA.
Nucleolus and nuclear membrane disappear.
Only animal cells.
Cylinder in centrosome.
Radiate from centrioles. Help equally divide chromatids between two offspring cells.
Spindle fibers move chromosomes to the center of dividing cell.
Chromatids of each chromosome seperate at the centromere and slowly move apart to opposite poles of dividing cells
Spindle fibers disassemble and chromosomes return to a less tightly coiled state. Nuclear envelope reforms. Opposite of prophase.
End of telophase. Division of cytoplasm and organelle. Animal=clevage furrow.
Plant= cell plate.
Formation of gametes
Stages of Meiosis
G1,S, g2, of interphase, Meiosis I(IPMATC) and meiosis ii (prophase ii, metaphase ii, anaphase ii, telophaseii.)
Meiosis ends with...
Four new cells
Prophse I processes
Synapsis or crossing over
Chromosomes line up next to its homologue.
Each pair of homologous chromosomes
Portions of a chromatid twist around another and break off. And attatch to adjacent chromatids.
Exchange of genetic material between maternal and paternal chromosomes.
Tetrads line up randomly along midline of the dividing cell.
Spindle fibers from each pole attach to the centromere of one homologous chromosome in each tetrad.
Each homologous chromosome of a tetrad moves to an opposite pole
Random separation of homologous chromosomes
Chromosomes reach opposite ends of the cell and cytokinesis begins
Only in reproductive organs on humans
Creation of ootids or egg cells. Here a diploid reproductive cell divides meitotically to produce one mature egg cell and three polar bodies
Without sex. Without mixing of genes
Offspring gets same diseases
Unicellular organisms reproduce
Uncontrolled cell growth
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