Biology - Meiosis + genetics (fertilization and development)

meiosis

• Chromosome number gets halved - producing 4 haploid daughter cells

• during interp in

non-disjunction

homologous pairs fail to separate into 2 haploid cells in anaphase + telophase 1.

Prophase 1

Chromosomes condense. Homologous chromosomes line up at the center of the cell and crossing over occurs. spindle fibres begin to show from centrosomes.

Metaphase 1

Homologous chromosomes randomly assemble at the metaphase plate.

Anaphase 1

Spindle fibres pull the homolous chromosomes apart. The sister chromatids are still attached.

Telophase 1 and cytokenisis

Sister chromatids arrive at the poles of the cell and begin to decondese. A nuclear envelope forms around each nucleus and the cytoplasm.

divided by cleavage furrow. result is 2 haploid cells. each cell contains one duplicated copy of each homologous chromosome pair.

Prophase 2

Sister chromatids condense. a new spindle begins to form. dissolution of the nuclear membrane

Metaphase 2

sister chromatids line up at the metaphase plate.

anaphase 2

sister chromatids are pulled apart into sepearate single chromosomes then uncoil into chromatin

Telophase 2 and cytokenisis

chromosomes arrive at the poles of the cell and decondense. nuclear envelopes surround the 4 nuclei.

cleavage furrows divide two cells into 4 haploid cells.

Diploid cells

2n - cell with two pairs oc each set of chromosomes.

Haploid cells

n - cell with one set of chromosomes

Zygote

A fertilized egg (undergoes fertilization)

Independent assortment

Chromosomes will split into daughter cells

homologous chromosomes

pair of matching chromosomes in diploid cells, with one inherited from each parent.

• pair up during meiosis to generate genetic recombination

Cross over

homologous chromosomes exchange genes

interphase

cell prepares for the next round of meiosis by duplicating chromosomes.

recombinant dna

Combination of two

Internal fertilization and internal development

the process of fertilization that occurs inside the body of an individual. It occurs mostly in land animals. Requires union of gamete cells.

When embryo/fetus develops inside an animal's body.

External development and fertilization

a mode of reproduction in which a male organism's sperm fertilises a female organism's egg outside of the female's body. Nearly all fish reproduce this way, so do oysters.

When the embryo/fetus develops outside an animal's body.