Gene Expression

Background Knowledge Gene: segment of DNA that codes for a specific structure of protein Protein: a macromolecule which helps regulate body processes Amino Acid: building blocks of proteins Gene Expression: the process of making protein from the information stored in DNA

Genes and Gene Expression

3-4 Transcription The strands of DNA are separated RNA polymerase binds at a promoter region RNA polymerase catalyses the formation of a mRNA chain using the DNA as a template and following the rules of complimentary base pairing – A with U – C with G Transcription ends at a terminator sequence

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3-6 Posttranscriptional Processing

3-7 Translation Process that occurs on ribosomes Turns mRNA into a polypeptide Involves rRNA, tRNA, and mRNA tRNA anticodons match with mRNA codons, and the rRNA catalyzes the formation of a peptide bond between the amino acids at the opposite end of the tRNA

3-8 Translation

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3-10 Regulation of Gene Expression All nucleated cells except germ cells have the full complement of DNA. During development, differentiation occurs and some segments of DNA are turned off in some cells while those segments remain “on” in other cells. During the lifetime of a cell, the rate of protein synthesis varies depending upon chemical signals that reach the cell. – Example: thyroxine from the thyroid causes cells to increase their metabolic rate. More thyroxine, higher metabolic rate; less thyroxine, lower metabolic rate.

Cell Life Cycle Interphase: phase between cell divisions – Replication of DNA – Ongoing normal cell activities Mitosis: series of events that leads to the production of two cells by division of a mother cell into two daughter cells. Cells are genetically identical. – Prophase – Metaphase – Anaphase – Telophase Cytokinesis: division of cell cytoplasm

3-13 Replication of DNA DNA strands separate The old strands become the templates for the new (complementary) strands to form Two identical DNA molecules are formed by semiconservative replication

3-14 Replication of DNA

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3-17 Cell Division Interphase – DNA replication occurs Mitosis – Prophase – nuclear envelope disintegrates, chromatin condenses, spindles attach to kinetochore – Metaphase – chromosomes are aligned at the nuclear equator – Anaphase – spindles separate the chromatids, cytokinesis begins – Telophase – chromosomes decondense, nuclear envelope reforms, cytokinesis continues Cytokinesis – cytoplasmic division, separate process from mitosis

3-18 Cell Division

3-19 Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at