1. MENDEL GENECTICS: The study of passing on simple traits to the next generation.

2. WHO IS GREGOR MENDEL?  Mendel was born in Austria and after completing college, he entered a monastery.  The monastery had a garden, and Mendel was able to use plants for his studies.  Mendel examined the patterns of inheritance.  Mendel published his work on the behavior of genes in 1865.

3. WHY PEAS?  Mendel used peas for his studies because:  They grow into mature plants quickly (60-80 days).  They produce numerous seeds quickly.  They have many observable characteristics that come in just two choices (such as purple and white flowers).  They can self-pollinate (fertilize themselves).

4. MENDEL’S PEA PLANTS  Mendel bred large numbers of pea plants and searched for simple patterns in seven traits of their offspring.  He studied one trait at a time (plant height, flower color, seed color, seed shape, pod shape, pod color flower position)

5. MENDEL’S BIG DISCOVERY!  When Mendel bred pea plants with the two traits (ex: a white flowered with a purple flowered plant) he found that one characteristic always seemed to disappear in the first generation offspring (ex: all white flowers).  Mendel called the trait that appeared the dominant trait.  The other trait that seemed to recede (go away) he called the recessive trait.

7. MENDEL’S BIG DISCOVERY!  Mendel allowed the first generation pea plants that showed the dominant trait to self-pollinate to produce a second generation.  When he did this, the recessive trait showed up again!

8. MENDEL’S BIG DISCOVERY!  Mendel then counted the number of plants with each trait that showed up in the second generation.  Mendel noticed that for each one of the seven traits the ratio of dominant trait to recessive trait in second generation was about 3:1.  The probability that the second generation has the recessive trait is ¼.

11. MENDEL’S APPLICATION OF THE RATIO  Mendel realized that his results could only be explained if each plant has two copies of the gene for each characteristic.  These two copies are called alleles.  Each pea plant receives only one allele for each characteristic from each parent and ends up with two alleles of its own.

12. PUNNETT SQUARE  A Punnett square is a diagram used to show all the possible combinations of alleles from parents.  You can use Punnett squares to predict the chances that each kind of offspring will occur.  Dominant alleles are symbolized with capital letters (TT).  Recessive alleles are symbolized by lowercase letters. (tt).

13. PUNNETT SQUARE  An organism that has only one kind of allele for a characteristic is called homozygous (ex: PP or pp).  An organism that has alleles for two different traits is called heterozygous (ex: Pp).

14. PUNNETT SQUARE – GENOTYPE VS. PHENOTYPE  Genotype – an organisms combination of alleles. (PP) – what the genes are.  Phenotype – an organisms physical appearance. (PP = purple flower)

15. PUNNETT SQUARE PRACTICE w W w W w

16. PUNNETT SQUARE PRACTICE w V V v