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Inside the Nucleus. Interest Grabber. Genes are made of DNA DNA is composed of individual units called nucleotides Three of these units form a code (codon). The order, or sequence, of the code determine the meaning of the message. DNA Nucleotides. Purines. Pyrimidines. Adenine. Guanine.
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Inside the Nucleus Interest Grabber
Genes are made of DNA • DNA is composed of individual units called nucleotides • Three of these units form a code (codon). • The order, or sequence, of the code determine the meaning of the message
DNA Nucleotides Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose
Structure of DNA DNA Structure Link Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
X-ray diffraction • Rosalind Franklin • X-rayed DNA from a calf thymus gland but had no idea what it was • James Watson saw this x-ray & interpreted DNA as a double helix
Chromosome Structure of Eukaryotes Nucleosome Chromosome DNA double helix Coils Supercoils Histones Chromatin
Chromosome Structure • 1 nanometer = 0.001 micrometer • 1 micrometer = 0.001 millimeter • So • 1 nm = 0.000001 mm
DNA Replication Original strand New strand DNA polymerase Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand
Replication – Making New DNA • Helicase separates two strands of DNA by breaking hydrogen bonds • Primase starts replication • DNA polymerase “polymerizes” the individual nucleotides & proof-reads the new DNA
Now that new cells have been made, new proteins will be needed. • HOW ARE PROTEINS MADE? • We first need to look at something called RNA
Messenger RNA Ribosomal RNA Transfer RNA Bringamino acids toribosome Combine with proteins tRNA mRNA Carry instructions rRNA DNA Ribosome Ribosomes RNA Concept Map RNA can be also called which functions to also called which functions to also called which functions to from to to make up
How is RNA different than DNA? • RNA • Contains ribose instead of deoxyribose • Single stranded • Nucleotide uracil replaces thymine
Transcription • Messenger RNA = mRNA • Carries amino acid sequence to the ribosome • Transfer RNA = tRNA • Carries amino acid to the codon on mRNA • Codon = 3 nucleotide bases on mRNA which “code” for an amino acid • Anticodon = 3 nucleotide bases on tRNA which match up with the codon
Transcription – Making a Copy of the DNA Transcription Link Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA
Transcription – Making a Copy of the DNA • RNA polymerase separates the DNA strands at a promoter region on the DNA • mRNA adds nucleotides in sequence • RNA polymerase falls off the DNA at a terminator sequence on the DNA
RNA Editing • Introns - Intervening sequence = Junk DNA • Exons – Expressed sequence • Introns are cut out of the mRNA • Exons are held together by a cap and a poly A tail
The Genetic Code - Amino Acid Sequence 4 x 4 x 4 = 64Possible Codons for 20 amino acids AUG = Start Codon Begins transcription AAU, GAU, AGU Stop Codons which end transcription
Translation (continued) Translation Link
Determining the Sequence of a Gene • DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations.
Gene Mutations: Substitution, Insertion, & Deletion Deletion Insertion Substitution Frameshift Mutation
Chromosomal Mutations Deletion Duplication Inversion Translocation
Typical Gene Structure Promoter(RNA polymerase binding site) Regulatory sites DNA strand Start transcription Stop transcription
Gene Regulation • Operon – A group of genes that operate together • Lac Operon = operon expressed in E. coli to use the sugar lactose • Operator – region where repressor protein binds • Promoter – region that signals beginning of operon
Tying it altogether - the lac Operon Gene E. Coli bacteria can synthesize lactase, which is an enzyme that breaks down lactose. Lactase is only synthesized in the presence of lactose. If there is no lactose in the environment, the gene is repressed. E. Coli has three genes that code for lactase. It also has an operator and a promotor. Without lactose, the lac repressor binds to the operator site. With lactose, the repressor is removed Once repressor is removed, RNA polymerase binds to the promoter RNA is transcribed, which is then translated, and becomes the lactase enzyme. Gene Regulation
Cell Growth & Reproduction • Why replicate the DNA? • To make new cells • To replace old worn out cells • To replace damaged cells
Cell Size Limitations • Why are cells so small? • Cell size Limitations • - Diffusion (The bigger the cell the slower the diffusion • - DNA (Large cells need more DNA to make more proteins) • - Surface area to volume ratio
Cell Size Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume
Chromosome Structure • Sister chromatids • Centromere – attaches chromatids • 46 Chromosomes in humans
M phase (Mitosis) Interphase G1 phase S phase G2 phase Prophase Metaphase Anaphase Telophase Concept Map – Cell Cycle Cell Cycle includes is divided into is divided into
The Cell Cycle G1 phase M phase S phase G2 phase
Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Figure 10–5 Mitosis and Cytokinesis Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming
Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming
Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming
Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming
Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming
Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming
Interphase • Events of Interphase • Cell grows • DNA replicates • Centriole replication • NOT PART OF MITOSIS