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Understanding Genes

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  1. Understanding Genes

  2. Where are genes found? Genes are segments of chromosomes. They are found within the nucleus of every living cell.

  3. What makes up a gene? Genes are composed of tightly coiled DNA.DNA is made up of deoxyribose sugar, phosphates, and bases.

  4. Why are genes important? Genes control the inheritance of traits and the production of proteins within cells.

  5. What is the difference between a chromosome an a gene? A gene is a segment of a chromosome that codes for a specific trait.

  6. How does the DNA “code” work?

  7. DNA is controlled by a “base-pairing rule” Because adenine always pairs with thymine, and guanine always pairs with cytosine, the order of the bases serves as a “code” that can be read & copied.

  8. What are some examples of traits that are genetically controlled? ALL inherited traits are regulated by genes!! Hair color, height, blood type, dimples, etc.

  9. A few examples of genetic disorders:

  10. In order for a cell to divide and pass on its traits, what must first happen to the DNA? DNA must first replicate, or copy itself. Notice gene “B” is always found in the same location on the chromosome, even after replication.

  11. One gene in our chromosomes is called CDH1. When this gene has the correct sequence of A’s, T’s, G’s, and C’s it provides the instruction for the cell to make a very specific protein.

  12. Hereditary stomach cancer is caused by an inherited error (mutation) in the CDH1 gene. This mutation prevents the correct production of the protein.

  13. The next three slides show some examples of “macro” mutations. Why do you suppose they’re called that?

  14. Which macro-mutation is shown in this photo? Deletion

  15. Sometimes segments on chromosomes can be exchanged without causing a harmful mutation. Chromosome segments are often exchanged during the process of “crossing over”

  16. This occurs during the cell division process (called “meiosis”) that produces gametes. Crossover usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome.

  17. Summarize some things that you now know about genes & chromosomes