DNA & the Genetic Code |
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Chromosomes
DNA contains all the instructions for an organism’s characteristic features. Because every organism has so many characteristics, there is a lot of DNA in a cell. To fit such a large amount of DNA into their cells, organisms arrange their DNA into packages. These packages are called chromosomes.
Each human cell contains 46 chromosomes, 23 from the mother, and 23 from the father. The number of chromosomes in a cell is dependent on the organism (for example, dogs have 78, while cats only have 38). Genes are located on the chromosomes and is an uninterrupted segment of DNA with coded instructions for an organisms inherited characteristics. These inherited characteristics are known as the alleles of an organism.
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THINK CRITICALLY:
Could the scientists from Jurassic Park ACTUALLY fill in the genetic code from amphibious creatures? Justify your opinion through research and discussion. NOT FOR MARKS... |
Cell Division: Growth & Repair: MITOSIS
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Cells for growth and repair reproduce through a process called MITOSIS. Mitosis CAN occur in the body cells of multicellular organisms and is responsible for the growth and cellular repair of a multicellular organism (but cannot provide an entirely new multicellular organism). Mitosis is also responsible for the reproduction of unicellular organisms.
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Cell Division & Reproduction: Multicellular Organisms: MEIOSIS
REMEMBER: The reproductive sex cells of plants and animals are called gametes. When 2 parent organisms reproduce, their gametes unite to create offspring. If the gametes contain the same amount of DNA as other cells, the zygote would end up with TWICE as much DNA than it needs.
Gametes undergo a SPECIALIZED division called MEIOSIS that allows them to only contain half the DNA of a normal cell. When 2 gametes unite the zygote formed has the "normal" amount of DNA (sperm provides the first half of the DNA and the ova provides the second half). Since each gamete only contains HALF the required DNA, it must divide twice. Read p.46-48 and use the button below to complete the note sheet:
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3.3 Patterns of Inheritance
Click on the image to test your ability to select specific traits with a breeding pair of dogs. Work your way through each of the levels.
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Section Review
- What connections can be made between genetic inheritance and the MAINTENANCE of biological diversity? Why is it important for us to apply our understanding to protect diversity?
- The arrangement of the chemicals on the rungs of a DNA ladder are known as what?
- DNA is organized into little packages. What are these packages called, and what is their function?
- How does cell division work in the body cells of animals?
- What is the difference between a dominant and recessive trait? Provide an example of these traits being passed on. What is the scientific name for these different forms of genes?
- Define AND provide examples of incomplete dominance.
- Create a flow chart showing the connection between DNA, genes and chromosomes.
- Explain why a carrier of a recessive allele may not have offspring with that trait.
- Compare mitosis and meiosis.