The Cell Cycle

Question 1

What are the phases of the cell cycle?

Answer 1

• Interphase
  
  • G1
  • S
  • G2
• M
  
  • Mitosis
  • Cytokinesis

Question 2

What happens in G1

Answer 2

• replicate mitochondria, robosomes, ER
• increase cell size
• Includes a restriction point

Question 3

What happens in S

Answer 3

Clone DNA to create 2 chromatids joined at the centromere

Question 4

What happens in G2

Answer 4

• Checkpoint
  
  • enough organelles?
  • correctly replicated DNA?

Question 5

What happens in M

Answer 5

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 6

Prophase

Answer 6

• Chromatin condenses into chromosomes
• centrioles go to poles
• spindle fiber and aster formation
• nuclear membrane dissolves
• kinetochore fibers attach to kinetochores

Question 7

Metaphase

Answer 7

microtubles align the chromosomes at the metaphase plate

Question 8

Anaphase

Answer 8

sister chromatids are pulled apart by shortening of the kinetochore fibers

Question 9

Telophase

Answer 9

• spindle apparatus disappears
• nuclear membranes form
• chromosomes relax
• cytoplasm and organelles are split in cytokinesis

Question 10

What are the phases of meiosis

Answer 10

• Prophase I and II
• Metaphase I and II
• Anaphase I and II
• Telophase I and II

Question 11

General discription of meiosis I

Answer 11

reductional division: homologous chromosomes are separated creating 2 haploid daughter cells

Question 12

prophase I

Answer 12

• chromatin condenses into chromosomes
• spindle apparatus forms
• nuclear membrane breaks down
• synapsis
  -homologous chromosomes (maternal and parental) form a tetrad held together by the synaptonemal complex
  -crossing over can occur at chiasmata

Question 13

Why is crossing over important

Answer 13

• can unlink linked genes which increases genetic variability of gametes
• explains Mendel’s 2nd law of independent assortment

Question 14

metaphase I

Answer 14

• tetrads align at the metaphase plate
• each homologous pair attaches to its own kinetorchore fiber

Question 15

anaphase I

Answer 15

• disjuction: the maternal and paternal chromosomes separate
• accounts for Mendel’s 1st law of segregation

Question 16

telophase I

Answer 16

• nuclear membranes form
• cells now haploid

Question 17

interkinesis

Answer 17

• may have a brief intermission between meiosis I and II
• chromosomes may uncoil a little

Question 18

general description of meosis II

Answer 18

equational division: sister chromatids are separated which does not chance ploidy

Question 19

prophase II

Answer 19

• nuclear membranes dissolve
• centrioles go to the poles
• spindle apparatus forms

Question 20

metaphase II

Answer 20

chromosomes align at the metaphase plate

Question 21

anaphase II

Answer 21

sister chromatids are pulled apart

Question 22

telophase II

Answer 22

nuclear membranes form

Question 23

differences between mitosis and meiosis

Answer 23

• mitosis
  -2n to 2n
  -somatic cells
  -homologous chromosomes do not pair
  -no crossing over
• meiosis
  -2n to n
  -sex cells only
  -homologous chromosomes pair
  -can have crossing over