Chapter 6.3

Question 1

How many stages of Meiosis are there? What are they?

Answer 1

Meiosis 1

Meiosis 2

Question 2

What happens during Meiosis 1?

Answer 2

Meiosis 1 is the first division is the reduction division when the pair homologous chromosomes are separated into two cells

Each intermediate cell will contain one full set of genes and cells are haploid

Question 3

What happens with Meiosis 2?

Answer 3

This is the second division is similar to mitosis and the pairs of chromatids present in each daughter cell are separated forming 2 cells

4 haploid cells are produced instead

Question 4

What is a diploid cell?

Answer 4

It is a normal cell that contains 2 chromosomes of each type - one inherited from each parent

Question 5

What happens during Meiosis 1?

Answer 5

[Prophase 1]
> Chromosomes condense and the nuclear envelope disintegrates, the nucleons disappears and the spindle formation begins as in prophase of mitosis
> Homologous chromosomes pair up forming bivalent
> Chromosomes have large molecules of DNA and move through the liquid cytoplasm as they are brought together results in the chromatids entangling. Known as crossing over.

[Metaphase 1]
> Homologous pairs of chromosomes pair assembles along the metaphase plate instead of the individual chromosomes
> Orientation of each homologous pair on the metaphase plate is random and independent of any other homologous pair
> Paternal chromosomes end up facing either pole known as independent assortment and result in many different combination of alleles facing the pole.
> Independent assortment of chromosomes in metaphase 1 result in genetic variation

[Anaphase 1]
> Homologous chromosomes are pulled to the opposite poles and chromotids stay joined to each other
> Sections of the DNA on “sister” chromatids which are entangled during crossing over now break off and rejoin - resulting in the exchange of DNA. The point at which chromatids break and rejoin are called chiasmata
> When exchange occurs this forms recombinant chromatids, which genes being exchanged between chromatids
> The genes being exchanged may be different alleles of the same gene, meaning the combination of alleles on the recombiant chromatids will be different from the allele combination on either original chromatids
> Genetic Variation arises from this new combination of alleles - the sister chromatids are no longer identical

[Telophase 1]
> The chromosomes assembles at each pole and the nuclear membranes reforms. Chromosomes uncoil.
> The cell undergoes cytokineses and divides into two cells.
> The reduction of chromosome number from diaploid to haploid is complete.

Question 6

What happens during Meiosis 2?

Answer 6

[Prophase 2]
> The chromosomes which consist of two chromatids, condenses and becomes viable again.
> The nuclear envelope breaks down and spindle formation begins.

[Metaphase 2]
> The individual chromosomes assemble on the metaphase plate
> Due crossing over, the chromatids will no longer be identical so there is independent assortment again and more genetic variation produce in Metaphase 2

[Anaphase 2]
> Anaphase 2 results in the chromatids of the individual chromosomes being pulled to opposite poles after division of the centromeres

[Telophase 2]
> Chromatids assemble at poles - chromosomes uncoil and form chromatin again. The nuclear envelope reforms and the nucleons become visible.
> Cytokineses results division in the division of the cells forming 4 daughter cell
{ Cells are haploid due to reduction division, they will become genetically different from each other and from parent cell - due the processes of crossing over and independent assortment.}

Question 7

What is a allele?

Answer 7

Is a different version of the same gene

Question 8

What does haploid mean?

Answer 8

Is the idea that each gamete contain half of the chromosome number of parent cell

Question 9

What is meiosis?

Answer 9

Is the idea that Gametes are formed from another form of cell division