Sections 1-3 Pages 54-79

Heredity Heredity is when traits are passed from parents to offspring.

Gregor Mendel Austrian, born 1822 Entered monastery at age 21, the monks taught him science. He was sent to Vienna to train in teaching but didn’t pass his final exam. Went back to monastery to focus on research. It was at the monastery garden he discovered the principals of heredity

Unraveling the Mystery- Pea Plants Mendel was curious why some pea plants had different characteristics (stem length, seed color, etc.) Pea plants were a good choice because they grow quickly and their were many different types. They were also able to self pollinate (resulting in true breeding plants). They are also able to cross pollinate (wind, bees, etc.)

Characteristics and Traits A characteristic is a feature that has different forms in a population. (Hair color) A trait is the different form. (Blonde, brown, black)

Use the Scientific Method on Mendel’s work Ask the question: How are traits inherited? Form a hypothesis: Inheritance has a pattern. Test the hypothesis: Cross breeding plants and offspring. Analyze the results: Identify patterns in inherited traits. Draw conclusions: Traits are inherited in predictable patterns. Communicate the results: Publish the results for peer review.

Mix and Match Mendel chose these plants because they were true breeding. He removed the anthers from a plant that produced round seeds. Then, he used the pollen from a plant that produced wrinkled seeds to fertilize that plant that produced round seeds. This allowed Mendel to select which plants would be crossed to produce offspring.

First Generation Experiment (F1) Crossed pea plants to study 7 different characteristics. He crossed purple flowers with white flowers. After this first generation he got all purple flowers. What happened to the trait for white flowers?

First Generation continued.. Mendel found that one trait was always present and one disappeared. Mendel chose to call the trait that appeared the dominant trait. Mendel called the trait that disappeared or fade into the background the recessive trait.

Second Generation Experiment (F2) He allowed the first generation plants to self pollenate. This recessive trait reappeared. For every 3 plants with purple flowers, there was 1 with white flowers. Pattern appeared for all 7 traits tested.

Ratios Try the math problems on page 60. What is the ratio found to calculate the dominant to recessive ratio? 3 to 1 or 75%/25% What other sciences use ratios? Chemistry and Physics

Thanks Mendel! It was only 30 years after Mendel died that his work got the attention and value it deserved!

Traits Gene: An inherited trait’s instructions Different forms (dominant and recessive) of genes are known as alleles. Dominant alleles are indicated with a capital letter. Recessive alleles are indicated with a lower case letter.

Genes Phenotype Phenotype: appearance or other detectable characteristics (color) Genotype Genotype: the entire genetic makeup of an organism, also the combination of genes for one or more specific traits Use letter combination Homozygous (2 dominant or 2 recessive alleles) example. PP or pp Heterozygous (1 of each allele) example. Pp

Punnett Square Used to organize all the possible combinations of offspring from particular parents.

Punnett Square

Probability The mathematical chance something will happen. Usually as a fraction or percentage. Try Math focus problem on page 65 Also try FOIL (first, outer, inner, last)

Incomplete Dominance Sometimes one trait is not always dominant over the other trait. These traits do not blend together, each has allele has its own degree of influence. Example Snap Dragon plant page 66

More about Traits One Gene, Many Traits Sometimes one gene influences more than one trait Many Genes, One Trait Some traits (eye color) are the results of several genes working together. Different combinations of alleles result in different eye color shaded.

Importance of the Environment If your genes make it possible for you to be tall and you do not eat a healthy diet, you may not reach your full height’s potential.

Reproduction Asexual Only one parent Makes exact copies Mitosis Most cells in your body and most single cell organisms Sexual Two parent cells join Two sex cells come together (different than body cells which have 46 chromosomes or 23 pairs) Human sex cells have only 23 chromosomes (half of what is needed) Each sex cell has only one of the chromosomes from each of the homologous pairs.

Meiosis Meiosis is the copying process that produces cells with half the usual number of chromosomes. Human egg 23 Human sperm 23

Meiosis Genes are located on chromosomes. During mitosis the chromosomes are copied once then the nucleus divides once. During meiosis the chromosomes are copied once then the nucleus divides twice. There are 8 steps in meiosis. One parent cell makes 4 new cells. Meiosis helped explain Mendel’s results (page 72).

Meiosis Step 1 Before meiosis begins, the chromosomes are in a threadlike form. Each chromosome makes an exact copy of itself, forming two halves called chromatids. The chromosomes then thicken and shorten into a form that is visible under a microscope. The nuclear membrane disappears.

Step 2 Each chromosome is now made up of two identical chromatids. Similar chromosomes pair with one another, and the paired homologous chromosomes line up at the equator of the cell.

Step 3 The chromosomes separate from their homologous partners and then move to opposite ends of the cell.

Step 4 The nuclear membrane re-forms, and the cell divides. The paired chromatids are still joined.

Step 5 Each cell contains one member of each homologous chromosome pair. The chromosomes are not copied again between the two cell divisions.

Step 6 The chromosomes then line up at the equator of each cell.

Step 7 The chromatids pull apart and move to opposite ends of the cell. The nuclear membrane forms around the separated chromosomes, and the cells divide.

Step 8 The result is that four new cells have formed from the original single cell. Each new cell has half the number of chromosomes present in the original cell.

Meiosis Animated hill.com/sites/ /student_view0/ch apter3/animation__how_meiosis_works.html hill.com/sites/ /student_view0/ch apter3/animation__how_meiosis_works.html

Meiosis and Mitosis Comparison hill.com/sites/ /student_view0/chapter3/animation__compari son_of_meiosis_and_mitosis__quiz_1_.html hill.com/sites/ /student_view0/chapter3/animation__compari son_of_meiosis_and_mitosis__quiz_1_.html

Sex Chromosomes Sex chromosomes carry genes that determine the offspring’s gender. Females XX Males XY 50%/50% Since males have one X and one Y it can result in a sex linked disorder such as color blindness or hemophilia

Genetic Counseling Use a pedigree diagram to help show the occurrence of a genetic trait in several generations of a family.

Selective Breeding Organisms that cross with desirable characteristic Flowers, fruit, etc..