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Introduction to Genetics

Introduction to Genetics. Gregor Mendel. Gregor Mendel is the “father of modern genetics” Austrian monk who did genetic experiments with pea plants Defined basic units of heredity. 1822-1844. Mendel used pea plants to conduct experiments. He concentrated on petal color and shape of peas.

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Introduction to Genetics

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  1. Introduction to Genetics

  2. Gregor Mendel • Gregor Mendel is the “father of modern genetics” • Austrian monk who did genetic experiments with pea plants • Defined basic units of heredity 1822-1844

  3. Mendel used pea plants to conduct experiments. He concentrated on petal color and shape of peas. Experiments led to basic genetic understandings such as: • What happens when two different plants breed? • How traits are passed from parents to offspring? • Basic understandings of dominant and recessive traits?

  4. Different traits Mendel observed:

  5. Why Peas? • Mendel could do two experiments a year • Lacked modern technology • Today scientists use organisms that reproduce quickly such as drosophila (fruit fly) which reproduces in 2 weeks or bacteria such as E. coli which reproduces within hours.

  6. Genetics • DNA are the blue-prints of all of your genetic information. • DNA is tightly wound into chromosomes • Your genetic information is on genes • Genes are located on chromosomes

  7. Your Genes and DNA • You are a combination of your parents. • You have ½ of your mom’s and ½ of your dad’s DNA • Remember Meiosis? • You have 2 pairs of 23 chromosomes (one from each parent) to make a total of 46 chromosomes.

  8. Human Chromosomes

  9. Genetic Traits • Genes you get from your dad are “paternal” and genes you get from your mom are “maternal” • These make up your traits. • Trait: characteristic determined by genes • Example: I have the trait for blue eyes

  10. Alleles • Each trait is carried on a chromosome stripe. • These stripes are called alleles. • Allele: form of a gene on a specific region of a chromosome

  11. Alleles for flower color Maternal Chromosome Paternal Chromosome

  12. Which of Your Parents Traits Will You Get? • Based on probability • For example, eggs have X chromosomes and sperm have either X or Y chromosomes. • XX= girl • XY= boy • What is the probability offspring will be a girl?

  13. Boy or Girl • 50% chance or 1 out of 2 • Only two different combinations! • XX or XY • Determining the sex of a baby is one example of probability. • But…it doesn’t always work that way…

  14. Dominant Alleles vs. Recessive Alleles • Certain traits are stronger then others. This means that they will more likely be expressed. • For example: If I mix black paint with white paint, what color will paint most likely be? • Black! It is a “stronger color”. • Dominant allele: one that is expressed physically (what organism looks like)

  15. Dominant Alleles vs. Recessive Alleles • What about the white paint? • Recessive allele: one that is masked or hidden by the dominant allele. • White paint would be an example of the “recessive color”. There is still white paint in the mixture, but it looks black.

  16. Terms To Know • Genotype: combination of two alleles (gene combination) • Homozygous: When the genes are identical (BB or bb) • Have to tell if it is dominant or recessive • Heterozygous: When the genes are different (Bb) • Phenotype: The observable trait (the trait you see)

  17. Boy: XY Girl: XX • What is the genotype for girl? • XX • Is boy homo or heterozygous? • Heterozygous XY (different letters) • Homozygous XX (same letters) • What is the dominant allele (X or Y?) • Y • How do you know? • Wherever Y is means a boy will form

  18. How genes are expressed • If an organism carries any combination of dominant genes, it will be expressed in an organism. • Recessive genes are only expressed when there are two recessive genes • Example XX in girls

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