Monday, March 17, 2008
Mon-Day 2
Bio- we reviewed the process of meiosis: where it occurs (in primary sex cells of the testes and ovaries), what happens to the number of chromosomes (gets halved from the 2n/diploid number to the n haploid number i.e. goes from 23 different homologous PAIRS of chromosomes to just 23 different chromosomes), and the differences between meiosis in males (equal cytokinesis creates four equal-sized sperm cells) and meiosis in females (unequal cytokinesis creates ONE egg and three much smaller "polar bodies).
We then saw what occurs when a sperm cell fertilizes an egg cell: a zygote forms, which then divides by mitosis to form two, then four, then eight etc. cells via CLEAVAGE (mitosis with the overall size of the ball of cells remaining the same). With sufficient cleavage, a ball of cells called a BLASTULA forms. Due to the DIFFERENT biochemical environments of the cells in this blastula, CELL DIFFERENTIATION begins to take place as the blastula becomes a three-layered GASTRULA. The three distinct layers of cells, the endoderm, the mesoderm, and the ectoderm develop into the organs that make up the inside, middle, and outer parts of your body, respectively. How can cells have identical DNA/chromosome but become different types of cells? Differentiation occurs when one type of cell, e.g. a skin cell, has certain genes chemically turned "off" while the genes that make the cell a skin cell (i.e. code for skin proteins/melanin) are turned/kept "on".
Tomorrow, we will review for the unit exam, which will be given on Wednesday.
Chem 7/8- we did more stoichiometry review today while going over most of the question types. The rest of the review packet annotated solutions will be posted later.
We then discussed our "Determining the Mass of a Product" lab, which we will finish writing on Wednesday.
Chem 9- we did more stoichiometry review today while going over most of the question types. The rest of the review packet annotated solutions will be posted later.
We then saw what occurs when a sperm cell fertilizes an egg cell: a zygote forms, which then divides by mitosis to form two, then four, then eight etc. cells via CLEAVAGE (mitosis with the overall size of the ball of cells remaining the same). With sufficient cleavage, a ball of cells called a BLASTULA forms. Due to the DIFFERENT biochemical environments of the cells in this blastula, CELL DIFFERENTIATION begins to take place as the blastula becomes a three-layered GASTRULA. The three distinct layers of cells, the endoderm, the mesoderm, and the ectoderm develop into the organs that make up the inside, middle, and outer parts of your body, respectively. How can cells have identical DNA/chromosome but become different types of cells? Differentiation occurs when one type of cell, e.g. a skin cell, has certain genes chemically turned "off" while the genes that make the cell a skin cell (i.e. code for skin proteins/melanin) are turned/kept "on".
Tomorrow, we will review for the unit exam, which will be given on Wednesday.
Chem 7/8- we did more stoichiometry review today while going over most of the question types. The rest of the review packet annotated solutions will be posted later.
We then discussed our "Determining the Mass of a Product" lab, which we will finish writing on Wednesday.
Chem 9- we did more stoichiometry review today while going over most of the question types. The rest of the review packet annotated solutions will be posted later.
# posted by C @ 1:37 PM 
