Lab 1: Mitosis and Meiosis

Question 1

In what stage of interphase does DNA duplicate?

Answer 1

S phase. Chromosomes are replicated to turn into two sister chromatids held together by centromere

Question 2

What happens in prophase?

Answer 2

Condensins begin to condense the chromatin into the chromosomes. Nucleolus begins to disintigrate

Question 3

What proteins hold the sister chromatids together until anaphase?

Answer 3

Cohesion proteins.

Question 4

What happens in metaphase?

Answer 4

mitotic spindles form from the two centrosomes. Made of tubulin polymerization. Spindles assemble and attach to the kinetochore section of the centromere of the double stranded chromosomes, making them line up on the metaphase plate.

Question 5

What are the three functions of microtubules that make up the spindle?

Answer 5

1) ones that anchor centrosome to cell membrane
2) ones that arch between centrosomes
3) ones that attach to chromosomes

Question 6

What happens in anaphase?

Answer 6

cohesins that were holding the sisterchromatids together begin to dissociate. Centromeres then separate, and the sister chromatids are pulled to opposite poles by the spindle apparatus. The kinetochore microtubles begin to de polymerize and the cell elongates.

Question 7

What happens in telophase?

Answer 7

chromosomes begin to decondense into the chromatin form. Nuclear membrane re forms and the spindle apparatus, astral rays, centrosome components etc disappear. Cytokinesis that divides the cytoplasm by forming a cell plate/cleavage furrow between the two newly formed duplicated chromosomes and organelles/

Question 8

Name a few key differences between mitosis and meiosis

Answer 8

• Synapsis (pairing of homologous chromosomes in M1) and crossing over occurs in meiosis
• only the separation of homologous chromosomes happen at A1, separation of sister chromatids happen in A2
• meiosis has 2 nuclear divisions with no DNA replication between divisions
• meiosis produces 4 genetically distinct cells with half the amount of DNA in each, whereas mitosis produces 2 genetically identical cells.

Question 9

Where does meiosis take place?

Answer 9

meiocyte cells. Oocytes for eggs and spermatocytes for sperm.

Question 10

How does meiosis create genetic diversity?

Answer 10

crossing over and independent assortment of homologous chromosomes during prophase 1.

Question 11

How many alignments are possible on the metaphase plate?

Answer 11

a diploid organism with 2n chromosomes will have 2n possible combinations of arranging its chromosomes during metaphase 1