dna/cell cycle

• deoxyribonucleic acid (dna) is a nucleic acid, the nucleotide has a phosphate, sugar, and nitrogen base
• dna is a double helix, can be wound or unwound, the "rungs" of the ladder are made of nitrogen bases, the sides are made of phosphate and sugar.
• the rungs of dna are held together by weak hydrogen bonds, the sides are held together by strong convalent bonds
• in nitrogen bases: adenine > thymine, cytosine > guanine
• in the semiconservative process: each dna strand is 1/2 & the exact same (complementary) of the original strand (template)
• once dna is replicated > the cell is ready to divide (after g2)
• During DNA replication, the enzyme helicase unzips the dna into 2 strands, the enzyme polymerase adds nucleotides to complete a new strand
• cells go thru the cell cycle to grow, repair, and replace worn out cells. cells aren't getting bigger/smaller they're just making more
• 3 stages of cell cycle: interphase, mitosis, cytokinesis
• interphase: cells spend most of life in, they grow, rest, & replicate DNA
• 3 phases in Interphase: g0 (cells rest), g1 (gap 1, cells grow), s (synthesis, replicate DNA), g2 (gap 2, prepare for next stage)
• Mitosis: only happens in somatic & eukaryotic cells, the cell divides into 2
• cytokinesis: final split of cells into 2 separate identical (daughter cells), animal cells have cleavage furrow, plant cells have cell plate
• if DNA is not replicated before mitosis > one cell could have all the DNA, or both cells could have half the required DNA
• chromosomes are made of chromatin, broken down into 2 chromatid strands held together by a centromere
• Prophase: DNA condenses into chromosomes > centrioles start to produce spindle fibers > nucleus starts to break down
• Metaphase: nucleus breaks down to let chromosomes out > chromosomes line up in middle of cell - attached to spindle fibers by centromere
• Anaphase: spindle fibers pull apart chromosomes to opposite sides of cell
• Telophase: chromosomes are at opposite sides of cell > new nucleus forms around chromosomes > cell starts to split > cytokinesis finishes split
• prokaryotic cells go thru binary fission instead of mitosis