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Published byBrittany Sims Modified over 8 years ago
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Biology STAAR Review #2 DNA / RNA / Protein Cell cycle Mitosis Meiosis
Replication Transcription Translation Mutations Cell cycle Mitosis Meiosis
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The Genetic Code: DNA – code for all life – in all cells
DNA coils to form Chromosomes A Gene is a section of DNA Genetic info is encoded in sequence of base triplets, called codons All cells contain Chromosomes Chromosomes are made of DNA Sections of DNA which code for genetic information are called genes
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Virtually all organisms share the same genetic code “unity of life”
Organism’s genotype is carried in its sequence of bases
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DNA – nucleic acid long chains of nucleotides
Nucleotide: 3 parts Phosphate Sugar Nitrogen Base G, C, A , T
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Partial chemical structure
DNA – double strand – twisted ladder or double helix Hydrogen bonds between bases hold strands together: A with T and C with G Hydrogen bond Ribbon model Partial chemical structure Computer model
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Nitrogenous base (A, G, C, or U)
RNA is also a nucleic acid different sugar, ribose U instead of T Single strand Nitrogenous base (A, G, C, or U) Phosphate group Uracil (U) Sugar (ribose)
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DNA Both RNA Nucleic acid Double Strand Nucleotides Single Strand
Thymine Nitrogen bases Uracil Sugar = Deoxyribose Sugar Sugar = Ribose Controls protein synthesis Controls heredity Phosphate Replicated before cell division Leaves nucleus Single strand Nucleotides Uracil Thymine Phosphate Replicated before cell division Controls protein synthesis Sugar Sugar=deoxyribose Nucleic acid Double strand Leaves nucleus Controls heredity Sugar=ribose Nitrogen bases
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Replication: DNA → DNA each strand is a template for a new strand
Occurs in nucleus – before cell division Produces 2 identical double helixes Purpose: Cell division, reproduction, growth Figure 10.4B
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Transcription: DNA → _____
mRNA Transcription: DNA → _____ One strand serves as template Occurs in nucleus Produces single strand Purpose: transfers genetic code for protein synthesis
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Translation: mRNA → _______
Protein Translation: mRNA → _______ mRNA leaves nucleus Occurs in cytoplasm Purpose: protein synthesis
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Translation: mRNA → Protein
The “words” of the DNA “language” – 3 bases called codons Sequence of amino acid chain = ________ Protein Ribosome – “reads” mRNA codon tRNA – brings matching amino acid Amino acids form chain to build protein
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Codon coding for amino acids
thr ACG = __________ Notice 3 other codons also code for same amino acid
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Transcription and Translation - Recap
Nucleus Cytoplasm What is Replication? DNA → DNA Where does it happen? Nucleus Cell membrane Ribosome
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Mutations can change the meaning of genes
Mutations (Gene or chromosomal) are changes in the DNA base sequence caused by errors: in DNA replication by mutagens environmental: UV radiation, chemicals, carcinogens Can be helpful harmful or neutral (silent) change of a single DNA nucleotide causes disease Effect depends on where mutation occurs 1. type of cell a. body (somatic) b. sex cell – passed to offspring 2. type of mutation
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Gene Mutations Point – changes only 1
Substitutions = 1 nucleotide changed UGC to UGA Inversion= reverse order UGC to CGA Frameshift – changes all after Insertions = nucleotides added – Deletions = nucleotides deleted – UGC to UGGC UGC to UC
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Chromosomal Mutations – large chunks affected
Deletion - (whole or part deleted) Insertion - (additional part added) Duplication - (extra copies of parts) Inversion - (reverses parts of chromosomes) Translocation - (parts break off and relocate)
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The Cell Cycle
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Five Phases of the Cell Cycle
G1 - primary growth phase S – synthesis; DNA replicated G2 - secondary growth phase M - mitosis C - cytokinesis Collectively these 3 stages are called Interphase
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Interphase - G1 Stage 1st growth stage after cell division
Cells mature by making more cytoplasm & organelles Cell carries on its normal metabolic activities
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Interphase – S Stage Synthesis stage DNA is copied or replicated
Two identical copies of DNA Original DNA
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Interphase – G2 Stage 2nd Growth Stage Cell gets ready for division
Copied DNA – checked for mistakes & repaired All cell structures needed for division are made (e.g. centrioles) Both organelles & proteins are synthesized
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Cell cycle Grows & makes organelles & cytoplasm Doubles DNA
Checks & repairs DNA errors
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Mitosis: Identical Daughter Cells
Two identical daughter cells Parent Cell
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Mitosis: Cell Division
Used for growth and repair Produce two new cells identical to the original cell Cells are diploid (2n) Chromosomes during Metaphase of mitosis Cytokinesis Anaphase Prophase Metaphase Telophase
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Mitosis 1. Prophase: 2. Metaphase: 3. Anaphase: 4. Telophase:
4 stages: 1. Prophase: The Centrioles begin to move apart. Chromosomes thicken The Nuclear membrane disappears 2. Metaphase: The centrioles are at the “poles” of the cell The chromosomes line up in the middle of the nucleus 3. Anaphase: The Chromosomes are pulled toward the centrioles by spindle fibers 4. Telophase: The nucleus begins to reform and the cell begins to split - cytokinesis
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Prophase Metaphase Anaphase Telophase Four Mitotic Stages
What are stages? 1 2 Prophase Metaphase Anaphase Telophase 3 4
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Name the Stages of Mitosis:
Early prophase Early Anaphase Metaphase Interphase Early Telophase, Begin cytokinesis Late Prophase Late telophase, Advanced cytokinesis Mid-Prophase Late Anaphase
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? ? ? ? ? ? ? Identify the Stages Early, Middle, & Late Prophase
Metaphase Anaphase Late Prophase ? ? ? Late Anaphase Cytokinesis Telophase
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Cell Division Mitosis Meiosis Cells divide for two reasons.
1. To create copies - Mitosis Meiosis 2. To create sex cells (gametes) - sperm egg
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Mitosis: Identical Daughter Cells
2 chromosomes Mother cell: 2 chromosomes Chromosome number the same, but cells smaller than parent cell
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Meiosis: Gamete - sperm or egg
The process of creating haploid sex cells called Gametes Gamete - sperm or egg Has two phases of “Mitosis-like stages” End result: Half the genetic material For humans: cell with 46 chromosomes forms cells with ___ 23
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Meiosis Forms Haploid Gametes
Meiosis must reduce the chromosome number by half Fertilization then restores the 2n number from mom from dad child too much! meiosis reduces genetic content The right number!
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Comparison of Divisions
Mitosis Meiosis Number of divisions Number of daughter cells Genetically identical? Chromosome # Where When Role 1 2 2 4 Yes No Same as parent Half of parent Somatic cells body cells Germ cells Ovaries / testes Whole life At sexual maturity Sexual reproduction Gametes (egg/sperm) Growth and repair
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