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Contains an organism's genome
complete collection of an organism's genetic information.
- -It's coade controls reproduction, development, and everyday functioning of living things
- - a cell's 'recipe book'
- -each individuual recipe = a gene
Where are genomes stored?
almost all DNA is stored in the nucleus
-each cell has a copy of the entire genome
What do DNA have instructions for?
protein production: DNA has the instructions and makes proteins to actually carry out necessary tasks.
How is the information in DNA stored?
- encoded in chhemical substances
- -Nitrogenous Bases
- -4 different bases make DNA: ADenie, Thymine, Guanine, Cytosine
sequence detemines genetic characteristics
- -In the nucleus, DNA makes a copy of itself onto mRNA
- -mRNA leaves nucleus, heads for a ribosome in the cytosol
- -a string of amino acids are put together according to directions in mRNA
Why do cells divide?
- replace dead cells
- for growth of an organism
- -cells can only grow so big before they are dysfunctional
- -therefore to grow, we need more (not BIGGER) cells
What are the 3 components of cell division?
- 1. Replication
- 3. Cytokinesis
Duplication of DNA
Separting DNA copies within the parent cell
Physical splitting of parent cell into 2 daughter cells
- double helix unwinds
- each strand serves as a template for constructing its new complementary strand
- SEMI-CONSERVATIVE MODEL
makes up chromosomes that DNA is packaged into.
Chromatin = DNA + associated proteins
Remain in an unduplicated state until DNA is replicated
- Once DNA is duplicated, chromosomes become:
- 2 identical sister chromatids
Chromosomes and DNA replication
What are the ways in which DNA can be found arranged?
- unduplicated state: remains loose in the nucleus
- duplicated: chromosomes consisiting of 2 identical sister chromatids take shape
- Chromosomes come in matched pairs
- -one member of the pair in inherited from each parent
- -they contain same genes but are NOT identical
- -each pair: homologous chromosomes
There are 46 chromosomes in humans, therefore 23 pairs
The cell cycle
- Mitoctic Phase (M phase):
- Interphase: cell is carrying out its job and preparing for cell division
- Mitotic phase: includes mitosis and cytokinesis
- how a cell divides.
- This is a multi-step process
- chromatin condenses into chromosomes
- double structure formed-composed of 2 indentical sister chromatids
- mitotic spindle begins to form
- chromosomes migrate toward center of nucleus
- nuclear envelope breaks down
- chromosomes line up on metaphase plate (attach to spindle fibers, microtubles)
- sister chromatids uncouple into individual chromosomes
- spindle pulls separated chromatids to opposie spindle poles
- spindle disassembles
- nuclear envelope reforms
- chromosomes decondense
- completes cell division by dividing the cytoplasm between the 2 daughter cells
- cell furrows and splits in two
Cell division in plant cells