IN What are gametes? Define Meiosis

Genetic disorders Explain Part A pg. 431 Homework Read

Open your book to page 496 With your group divide two genetic disorders between pairs Read and take notes about your decided disorder Share your information with the other pair Check with my notes to see you have all important information

Case studies of two genetic disoders Huntington’s disease- a dominant genetic disorder that causes degeneration of the central nervous system. Symptoms occur after 35 NO cure Disease causes the brain and nerves to slowly shutdown for up to 15 years, then person dies Genotype Hh or HH

Cystic fibrosis -- a recessive genetic disorder that affects the respiratory system. Symptoms show at birth Lungs are clogged with thick mucus Affects digestive system as well because of mucus Possibilities range between races Genotype cc NO cure, person usually dies at a young age However, antibiotics, vapor therapy, and chest thumping help

Other genetic disorders to research: Down syndrome Sickle-cell

Would you test to see if you and your partner carry genetic disorders? What are the advantages of knowing you have alleles for genetic disorders? What are the disadvantages of knowing you have alleles for genetic disorders?

Understanding Patterns of Inherited Patterns Gametes -- How genetic information is passed on from one generation to the next Sperm(male)Egg(Female) Only have half the information 23 Chromosomes

Meiosis --- process that reduces the amount of genetic information in a cell by half. How gametes are produced VERY important process, because it reduces the amount of genetic information so that it doesn’t continue to build up Explains why patterns of inheritance often are predictable

Meiosis: The Mechanism behind patterns of inheritance In all cells(46 chromosomes), chromosomes are in pairs; This is called diploid (2n) For each pair; one chromosome from mom one chromosome from dad Gamete(23 chromosomes) only contain 1 chromosome from each pair; This is called haploid (n)

MOMnnDAD 2n

Chromosome from dad nChromosome from mom n DNA synthesis: each chromosome doubles Cell begins to divide in half 2n Cell division 1 n n Cell division 2 n n n n

Before meiosis, each chromosome doubles; DNA synthesis First cell division occurs and doubled chromosomes separate Each offspring cell contains one doubled chromosome Second cell division occurs and doubled cell separates into two cells Results in a total of 4 offspring cells (daughter) Each offspring cell contains one chromosome from original pair

Principle of segregation --- during meiosis, chromosome pairs separate so that each of the two alleles for any given trait appears in a different gamete. Gg G g G g

Watch DVD “Meiosis” and add additional notes to help with you understanding of the concept Meiosis web animation

Tracking Genes through Meiosis Use figure 11.9, your journal notes, and modeling clay to track how meiosis affects the distribution of the 4 chromosomes.

1. On a large sheet of paper, draw circles to represent a cell undergoing meiosis. On the last set of four circles. Refer to page Use modeling clay to form 2 pairs of chromosomes about as thick as a pencil. Make one pair longer than the other. Red is from female parent Blue is from male parent

3. Use the letters provided and press them gently into clay. C= cream eye c= tan eye W= white wingw=spotted wing Eye color on long chromosome and Wing color on short chromosome 4. Place your chromosome models in the large circle at the top of your sheet of paper

replicate 5. Prior to meiosis, the chromosomes replicate. Make more clay models with labels to represent this step. 6. Using your cell diagram circles, move your chromosome models through the process of meiosis. In your journal, draw the chart you created

7. Answer the following questions: A. In your model, what is the genotype of each sperm for eye color and wing color? B. What other genotypes are possible? C. At what point would you change how you positioned your chromosome models to obtain the other possible genotypes?

Interphase

Interphase (synapse)

Meiosis I

Meiosis II

Interphase (synapse)

Crossing-over

Meiosis I

Meiosis II