chapter 11 section 4 notes biology

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Meiosis
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2 complete sets of genes are found in most adult organisms
Homologous- ​each of the 4 chromosomes from male parent has a corresponding chromosome
from female parent
Diploid Cells- ​holds both sets of homologous chromosomes; shown as 2N; somatic cells
Haploid Cells-​ holds only one set of homologous chromosomes; shown as N; sex cell
Zygote- ​ a fertile egg
Acquired Characteristic- ​characteristic one receives after they are born; may be due to
environment, a disease, injury, etc…
Inherited Characteristic- ​characteristic one receives from the genes of the parent; eye color,
heright, hair color, etc...
Phase of Meiosis
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Meiosis is a process by which the number of chromosomes per cell is cut in half
Produces the gametes, which are sex cells
2 distinct divisions
Stant out with diploid cells (2N) and at the end of the second division, there will be 4
haploid cells (N)
Meiosis I
1. Prophase I- ​crossing over occurs which provides genetic variation; this forms a Tetrad,
which is 4 chromatids; homologous chromosomes paired together
2. Metaphase I- ​the paired homologous chromosomes line up in the middle
3. Anaphase I- ​the paired homologous chromosomes are pulled apart
4. Telophase I and Cytokinesis-​ 2 new cells are reproduced and they are still diploid cells
(2N)
Meiosis II
1.
2.
3.
4.
Prophase- ​ in Meiosis II there is no prophase
Metaphase II- ​homologous chromosomes line up in the middle
Anaphase II- ​the paired chromatids separate
Telophase II and Cytokinesis- ​4 new haploid cells are formed. They have half the
number of chromosomes compared to the original cell at the beginning of Meiosis I
Comparing Meiosis and Mitosis
Replication and Separation of Genetic Material
- Mitosis produces exact copies; clones
- Meiosis has half the number of chromosomes
Changes in Chromosome Number
- Mitosis has the same number of chromosomes at the end
- Meiosis has half the number of chromosomes
Number of Cell Divisions
- Mitosis is a single cell division so they are genetically identical
- Meiosis is two rounds of cell division that produce 4 genetically different cells
Step by step process
1.
2.
3.
4.
5.
6.
7.
8.
9.
Cell undergoes DNA replication
Crossing over occurs
Homologous chromosomes line up in the middle
Spindle attach
Spindle pull homologous pairs apart
2 daughter cells
Sister chromatids separate from each other
Individual chromatids move to end of cell
4 haploid cells
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