DNA Structure TEK 6A: Each nucleotide is constructed of 3 parts: Identify components of DNA, and describe how information for specifying the traits of an organism is carried in the DNA Each nucleotide is constructed of 3 parts: Why DNA is often compared to a ladder? DNA is similar to a ladder: the rails of a ladder represent the sugar-phosphate backbone of DNA, and the rungs of a ladder represent the nitrogen base. How is a ladder different from DNA? DNA is twisted while a ladder is flat and that a “rung” in the DNA molecule is made of two bases, while the ladder’s rung is a single unit. The P of one nucleotide is bonded to the sugar of another nucleotide. a PHOSPHATE group, a SUGAR molecule & 1 of 4 NITROGEN bases Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

Because of the hydrogen bonds, Thymine Adenine Cytosine Guanine Because of the hydrogen bonds, Adenine can only bond with Thymine & Guanine can only bond with Cytosine *Apples in Trees *Cars in Garages A’s with T’s C’s with G’s Notice the elements in a nucleotide: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorous (CHONP)

DNA has a double helix structure

Cell Cycle & Growth TEK 5A: describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis, and the importance of the cell cycle to the growth of organisms.

Cell Cycle Overview Three main stages of the cell cycle: Interphase: the cell grows, carries out cellular functions, and replicates its DNA. Longest phase. Includes G1, S, & G2 Mitosis: the cell’s nucleus and nuclear material divide; includes four sub-stages. Includes Prophase, Metaphase, Anaphase, Telophase (PMAT). Cytokinesis: cell’s cytoplasm divides, creating two new cells.

1. Interphase: (G0), G1, S, G2 Most of the cell’s life is spent in Interphase Longest phase –(90% of cell’s life) G1 – Cell growth 1. Cell increases in size. 2. Makes new proteins and organelles. G0 – Resting Phase 1. If cells don’t go into this phase it could cause cancer (tumor) S – DNA Synthesis (replication) 1. Chromosomes are copied. 2. New DNA molecules are made. G2 – final cell growth 1. Shortest phase 2. Check for mistakes in new DNA 3. Prepare for nuclear division (mitosis)

2. Mitosis – nuclear division Used for the replication of body (somatic) cells 4 Phases: (PMAT) Prophase - primary Metaphase - middle Anaphase - away Telophase - two nuclei

3. Cytokinesis The end of M-Phase (M-phase = Mitosis + Cytokinesis) Each daughter cell has an identical set of chromosomes Animal cells The cell membrane is drawn inward forming a cleavage furrow until the cytoplasm is pinched into 2 nearly equal parts Plant cells A cell plate gradually develops into a separating membrane.

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