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Meiosis
Terms:
Heredity
Trait
Genetics
Fertilization
Pure-bred
Gene
Alleles
Dominant allele
Recessive
Hybrid
Phenotype
Genotype
Homozygous
Heterozygous
Meiosis
Crossing-over
Homologous chromosomes
Tetrad
Diploid
Haploid
Gamete
-
Content:
46=magic number: somatic cells all have 46 chromosomes.
N=the number of chromosomes from 1 parent.
Diploid=2n, two sets of chromosomes
Karyotype= a map of chromosomes in the human body.
23= the “sexy” number
Gametes= any reproductive cells (sperm and egg cells.)
Haploid= half the number of chromosomes in a normal cell.
1n= 23, haploid.
All human gametes have 23 chromosomes
Meiosis= cell division of reproductive cells only.
End goal= 4 haploid daughter cells.
Daughter cells are not identical due to crossing-over
Crossing-over= allows for genetic diversity.
Concepts/Skills:
There are two types of phases: meiosis 1 and meiosis 2.
Interphase: DNA replicates.
Prophase 1: DNA condenses into chromosomes and crossing-over occurs with homologous chromosomes
Metaphase 1: Nuclear membrane dissolves, and spindle fibers attach to homologous chromosomes at the
centromere when they join to form tetrads.
Anaphase 1: Spindle fibers pull the chromosomes toward the centrioles taking 2 sister chromosomes per side.
Telophase 1: Nuclear envelope reforms, with 2 sister chromosomes per nucleus.
Cytokinesis: Cell membrane pinches in forming 2 daugher cells with non identical homologous chromosomes.
Prophase 2: Nuclear envelope breaks down, and new spindle fibers form.
Metaphase 2: Spindle fibers attach to both sides of the centromere.
Anaphase 2: Spindle fibers pull the sister chromosomes apart.
Telophase 2: Nuclear envelope reforms.
Cytokinesis: Cell membrane pinches. Chromosomes become chromatin.
Diagrams:
Mitosis:
-No crossingover.
- Makes 2
cells.
-2 cells are
identical.
-1 division.
-Diploid
cells.
Both:
-DNA
replication.
-PMAT
Sample questions:
1. What are the differences between meiosis and mitosis?
2. What is a karyotype?
3. How many chromosomes are in a somatic cell?
4. What is a gamete?
5. What is the end result of meiosis 2?
6. Why does crossing-over make meiosis different from mitosis?
7. What are the phases of meiosis?
8. How are meiosis and mitosis similar?
9. What are tetrads?
10. How many sets of chromosomes does a diploid cell have?
Meiosis:
-Haploid
cells.
- Form
tetrads.
- 2 divisions.
- Crossingover occurs.
-Produces 4
cells.