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Introduction to Genetics

Introduction to Genetics. Genes= set of instructions for one protein; section of chromosome region of DNA that controls a hereditary characteristic (by making a particular PROTEIN!!). Introduction to Genetics. Trait= characteristic that is expressed and may vary from one individual to another

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Introduction to Genetics

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  1. Introduction to Genetics Genes= set of instructions for one protein; section of chromosome region of DNA that controls a hereditary characteristic (by making a particular PROTEIN!!)

  2. Introduction to Genetics • Trait= characteristic that is expressed and may vary from one individual to another • Heredity= passage of genetic information from parents to offspring

  3. Allele: different forms of a gene found on homologous chromosomes

  4. Heterozygous: Having two different alleles for a single trait. • Homozygous: Having identical alleles for a single trait. • Genotype:The genetic makeup of an organism • Phenotype: An organism's expressed physical traits.

  5. Remember…these are separated during meiosis!! • Homologous chromosomes • Alleles

  6. But before all this cool stuff was known….. It all started with a monk and his pea plants…..

  7. Began with Mendel

  8. The modern science of genetics was founded by an Austrian monk named Gregor Mendel. • Mendel was in charge of the monastery garden, where he was able to do the work that changed biology forever. • Mendel carried out his work with ordinary garden peas, partly because peas are small and easy to grow. A single pea plant can produce hundreds of offspring. • Today we call peas a “model system.”

  9. Cross-pollination allowed Mendel to breed plants with traits different from those of their parents and then study the results.

  10. Gregor Mendel…the “father” of genetics

  11. Mendel’s Conclusions

  12. Dominant Trait : the trait will always appear if the gene is present (Capital letter) (Dominant allele= dominant gene) • Recessive Trait: the trait that will appear if there are two copies of a gene…..otherwise this trait will be hidden by the dominant trait!! (lower case letter) (Recessive allele=recessive gene….the one that can be covered up)

  13. Principle of Segregation • Allele pairs separate or segregate during formation of gametes (MEIOSIS) and recombine during fertilization

  14. Meiosis Explains this

  15. Principle of Independent Assortment • Alleles for different traits are separated independently of each other

  16. Mendel’s Principles • The inheritance of biological characteristics is determined by individual units called genes. • When two or more forms (allele) of the gene for a single trait exist, some alleles may be dominant or recessive • In most sexually reproducing organisms, each adult has two copies of each gene– one from each parent. These genes segregate from each other when gametes are formed. • Alleles for different traits usually separate independently of each other

  17. Punnett Squares • chart which shows/predicts all possible gene combinations in a cross of parents (whose genes are known). • Actually…..shows possible alleles parents may contribute!!

  18. Dihybrid Cross

  19. Probability and Punnett squares • Why are the principles of probability able to be used to predict the outcome of genetic crosses? • Think about the “segregation of alleles”!!

  20. Heterozygous: Having two different alleles for a single trait. • Homozygous: Having identical alleles for a single trait. • Genotype:The genetic makeup of an organism • Phenotype: An organism's expressed physical traits.

  21. Inheritance of Traits • During fertilization…the male and female parents each contribute genetic information…to create the zygote • Zygote: fertilized egg; cell formed by union of gametes

  22. Species chromosome number: the number of chromosomes normally in the body cell of the organism • Same from generation to generation

  23. Karyotype: photograph/chart of chromosomes in an organism arranged in pairs • Can tell gender….and certain diseases

  24. Kleinfelters Syndrome

  25. Genetics so far…… Simple dominant/recessive one trait crosses! Now…… Incomplete Dominance: a blending of traits; neither allele is completely dominant Codominance: Each trait is expressed; both alleles are dominant

  26. Incomplete Dominance • Alleles are neither dominant or recessive • The heterozygote phenotype is a blending (lies somewhere between the two)

  27. Codominance • In a heterozygote…..both traits are expressed separately…both are dominant • Example…..

  28. Codominance Codominance helps to explain the inheritance of Human Blood Types

  29. Human Blood Typing • Blood type is determined by antigen found on red blood cell

  30. Codominance and Multiple Alleles!! • There are more than two alleles (gene possibilities) (Multiple Alleles) • A (I A), B (IB), and O(i) • Both A and B are dominant(Codominant) • O is recessive

  31. If an antigen is introduced to a person that cannot recognize it…they will make antibodies against it…..and attack it! • This will cause the blood to clump…clots... • So blood types need to be matched • If the person can recognize it…they can have it!!

  32. Blood Typing Process!!

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