1. Discuss the life of Gregor Mendel. What organism did he work with and what were his major contributions to genetics? What did he do that other scientists did not do?
 

• An Austrian Monk (1822-1884) known as the Father of Genetics
• Began his work around 1860
• Studied how traits are passed between generations using  garden peas plants.
• Chose pea plants because of the distinct (either or) traits (Seven of them: Plant height, seed shape, seed color,flower color, flower position, pod color, pod shape) and the quick reproductive cycle. He kept track of the offspring and applied mathematics in his analysis of each generation.
• The traits occur in two distinct forms, for instance, the color of the pea flower is either white or purple. He developed true breeding strains that when crossed with another true breeding plant would always produce that trait. For example, a true breeding tall plant when crossed with another true breeding tall plant would always produce tall offspring. He then crossed a true breeding tall plant with a true breeding short plant and took careful note of the outcomes.
• Found that the inheritable material came in pairs and these traits are passed down through generations.
• "Law of Segregation"-- genes randomly separate during meiosis, so an organism  passes only some of its traits to each offspring
• "Law of Independent Assortment" --traits are passed down independently of other traits. 
• Mendel realized this through countless crossings with  pea plants. This occurred long before anyone knew about  DNA, chromosomes, genes, etc.
• Applied mathmatics and statistics in his anaylysis which was not done before by other scientists.

• Genes found on sex chromosomes--the X or Y chromosome (usually the X). Remember women have XX and men have XY. Humans have 23 pairs or 46 chromosomes, 22 pairs are autosomes and one pair (xx or xy) are sex chromosomes.
• Since men have only one X chromosome, and if the disorder is inherited from his mom (a carrier because she has one X chromosome with the trait and one normal X chromosome that masks the trait), he will have the affliction. A woman has two XX so the disorder will be masked because of the dominant allele present on the other X chromosome. A man with the disorder will have all normal sons (since they receive the X chromosome from mom) and all daughters will be carriers (since he can only give them the disfunctional X chromosome).
• Examples: hemophilia (blood clotting disorder), Duchenne muscular dystrophy, colorblindness are disorders located on the X chromosome.
• hemophilia: lack of the ability to clot after even a minor scratch or bruise and is caused by the absence of a blood clotting factor. Can be treated, but in the past was fatal.
• Duchenne muscular dystrophy: A fatal X-linked recessive disorder that results in the wasting away of muscular tissue. Onset is usually around 6 yrs of age, with a lifespan of about 20 yrs. The Duchenne muscular dystrophy gene and the protein it codes for has been isolated
• Colorblindess: Red-green colorblindness is caused by a recessive sex-linked allele. The person who is affected by this disorder has difficulty distinguishing  red colors from green colors. The frequency of males with this disorder is about 10% of the population.
• For complete credit on this question you MUST include a punnett square demonstrating how the disorder is passed down to the offspring. Remember whenever doing a punnett square for sex linked traits you MUST use x's and y's (xx or xy). You get to choose how you want to demonstrate the genetics (whether you use mom as a carrier or dad with the affliction - you set up the square and explain it)
• You will receive 2 pts for a correct definition of sex linkage, 2 pts each for an example (4pts total), and 4 points for illustrating with a short explanations and a punnett square.

• Gene Mutations: A mutation that results from a change within the structure of a gene (a change in one or more nucleotides) during DNA replication; one allele of a gene changes into another allele. Such mutations arise spontaneously or from certain agents.
• Two types are:
• Nucleotide base substitutions--(called a "Point Mutation") a base pair (A-T, C-G) is replaced with another.  A changes to G or G to A or C changes to T or T to A. Many disorders are a result of point mutations--sickle-cell anemia is caused by  a single base change.
• Frameshift--(omission or repetition) addition or deletion of nucleiotides causing a shift in the way the DNA strand is translated. The affected sequence may change the whole protein product.
  • Example: THE FAT CAT ATE THE RAT - take out the F in fat, all the letters shift over
  • it reads THE ATC ATA TET HER AT.... doesn't make much sense does it?

   

• Chromosome Mutation: Change in the structure of a chromosome.
• Nondisjuction--failure of the normal segregation of homologous chromosomes to opposite poles during meiosis. Results in a gamete without a chromosome (Turner syndrome)  and a gamete with an extra chromosome (trisomy--Downs syndrome & Klinefelter syndrome)
• Deletion--a part of a chromosome is broken off and lost
• inversion--part breaks off and reattaches to another part of the chromosome end.
• duplication--part of chromosome is duplicated , doubling some genes
• translocation--a chromosome part breaks off and reattaches to a different nonhomologous chromosome.

Information on the HUMAN GENOME PROJECT   http://www.ornl.gov/hgmis/project/info.html

Other sites that might be of help to you:

Morgan's genetic site complete with quizzes!

An intro to genetics page

check out this site for PCR animation - it's so cool! (click on "Media/ Animation")