Download Biology Ms. Frick 1-7-16 Homework: Finish Pogil, if did not get done

Biology
Ms. Frick
1-7-16
Homework:
Finish Pogil, if did not get done in class, due Friday
Quiz:
Friday over Sections 6.1 and 6.2 (open notes, handwritten on separate paper)
Pages 158-166
Test:
Tuesday over Unit 4, Part B (includes Section 6.1/6.2 and 6.6—pages 179-181)
Today’s Activities:
 Took notes and began working on pogil over meiosis
New Learning: Meiosis
Two types of cell reproduction
1. Asexual reproduction (mitosis) – two identical copies of the parent cell are produced to replace
damaged cells and for growth
a. Asexual reproduction occurs in somatic cells (body cells ex. Kidney, eye, skin, etc.)
2. Sexual reproduction (meiosis) –an organism creates a “reproductive cell” or Gamete with
exactly half the required DNA. One organism’s gamete combines with another organism’s
gamete to form a cell with the full set of required DNA or Zygote
a. Sexual reproduction only occurs in reproductive cells
Chromosomes
A human cell has 46 chromosomes which come in 23 pairs.
 23 chromosomes from your mother and 23 chromosomes from your father
 Each set of chromosomes is referred to as a homologous pair
Homologous Chromosomes: one of a matching pair of chromosomes.
One from the mother/one from the father – both code for the same gene
Ex.
Chromosome from each parent coding for eye color are homologous because, even though they
come from each parent, they are both used to determine eye color in the offspring

One from each parent cell has homologous pairs of each chromosomes just before cell division,
and every organism has a set number of homologous pairs in each cell
--again, one chromosome comes from each parent; they are NOT exact copies of each other
--however, the sister chromatids are exact copies of each other
--these chromosomes have copies of the same genes, although the two copies may differ
In Sexual Reproduction, a gamete cell from the mother and a gamete cell from the father fuse, resulting
in a genetic mixture of both parents (this process is called fertilization).
 Because two cells are fusing together, they each must only have half of the correct number of
chromosomes, so that the produced cell has a single, complete set of DNA
Cell Titles Based on Number of Chromosomes
Diploid cell (2n):
a cell that contains both chromosomes in a homologous set of chromosomes
(one from mother and one from father) in humans: 46 chromosomes
Haploid cell (1n):



a cell with a single set of chromosomes
In humans, it’s 23 chromosomes
Gamete (1n): an egg or sperm reproductive cell with a single set of chromosomes
One diploid cell becomes 4 gametes (or reproductive cells)
When 2 gametes combine, it forms a zygote (2n)
Zygote:
a single diploid (2n) cell that forms when a haploid egg cell fuses with a haploid sperm
cell
Meiosis:
the process of nuclear division that one divides a diploid cell into 4 haploid cells
The DNA is copied only once, however, the cell is divided twice


Meiosis I
(before meiosis begins, DNA is copied)
divides homologous chromosomes producing two haploid cells with duplicated
chromosomes
Prophase I:
Metaphase I:
Anaphase I:
Telophase I:
Meiosis II
nuclear membrane breaks down and homologous chromosomes pair up
homologous chromosomes line up along the center of the cell
paired chromosomes are pulled apart and move to opposite sides
nuclear membranes reform and the cell undergoes cytokinesis
applies to both cells produced in Meiosis I
DNA is NOT copied again
Prophase II:
Metaphase II:
Anaphase II:
Telophase II:
Overview:
Because the cells are divided twice, there are 2 overall stages of meiosis
Meiosis I and Meiosis II
Each stage of Meiosis has 4 phases of division
nuclear membrane breaks down
chromosomes (with 2 sister chromatids) line up along the center of the cell
sister chromatids are pulled apart and move to opposite sides of the cell
nuclear membranes reform and the cell undergoes cytokinesis
Meiosis

Meiosis produces 4 haploid cells with a combination of chromosomes from both
the mother and father

Two haploid cells can now fuse together to form a diploid cell called a zygate