Cell division and cell cycle

Question 1

What is the cell cycle

Answer 1

• natural cycle of events that occur in the life of a cell
• during most of the cell cycle interpahse occurs
• interphase is a time of high metabolic acitvity for the cell

Question 2

What happens during interphase

Answer 2

• there is a replication of organelles such as mitochondria and chloroplasts which have their own DNA
• new organelles are made
• there is a synthesis of ATP and proteins
• increases in cell size
• there is a replication of DNA

Question 3

What is cytokenesis

Answer 3

• division of the cytoplasm to create 2 new gentically identical cells

Question 4

What is the difference of cell division in plant cells than to animal cells

Answer 4

• no centrioles in plants
• in cytokenesis a cell plate (droplets of cell wall material) develops to from the centre out instead of cleavage from the outside in as in animal cells

Question 5

What isthe significance of mitosis

Answer 5

• the signisficance of mitosis produces genetically identical cells to the parent cell giving genetic stability
• growth
• repairing damaged cells
• replacement of old worn out cells
• asexual reproduction

Question 6

How is the cell cycle controlled

Answer 6

• by genes
• if gene refulate the cell cycle damages uncontrolled mitosis can occur
• rapid replication of cells form tumours leading to cancer
• oncogenes are genes that cause cancer

Question 7

What is prophase

Answer 7

• chromosomes condene and become visible
• centrioles more to opposite sides of the cell in animal cells
• spindle forms from microtubules
• nuclear envelope disintegrates

Question 8

What is metaphase

Answer 8

• centromeres or chromosomes attach to pindle and line up on the equator

Question 9

What is anaphase

Answer 9

• spindle fibres shorten
• centromere separates and individual chromatids are pulled to the poles centromere first

Question 10

What is telophase

Answer 10

• spindle breaks down
• chromosomes uncoil
• nuclear envelope reforms

Question 11

What is meiosis

Answer 11

• takes place in reproductive organs produce cells that are haploids for sexual reproduction (gametes)
• occurs in 2 cell divisions following interphase

Question 12

Describe prophase 1

Answer 12

• differes from prophase in mitosis as chromosomes form bivalents (pairs of homologous chromosomes)
• arms of the chromatids may cross over forming chiasmata
• here genetic material can be exchanges between homologous chromosomes therfore increasing the variation in inherited genomes

Question 13

Decribe metaphae 1

Answer 13

• homologous chromosomes arrange themselves in pairs along the equator
• independent assortment occurs here where the hoologou chromosomes from parent 1 and parent 2 and arrange themselves randomly along the spindle facing each pole

Question 14

Describe anaphase 1

Answer 14

• the chromosome bivalents seperate as each chromosome is pulled by its centromere whcih does not split towards the opposite pole

Question 15

Describe telophase 1

Answer 15

• nuclear envelopes reform around the chromosomes at poles
• in meiosis prophase II occurs after telophase I
• asa the chromoome pairs have seperates chromosomare are no longer in pairs and the cells are haploid

Question 16

Describe the second cell division for meiosis

Answer 16

• events occur in each new nucleus in the second phase of meiosis exactly as they do in mitosis
• cytokenesis occurs resulting in 4 genetically vaired cells

Question 17

Describe the differences between mitosis and meiosis

Answer 17

Mitosis
* 1 division
* 2 cells formed
* diploid
* genetically identical
* no homologous chromomes
* no crossing over
* no segregation of homologous chromsomes
Meiosis
* 2 divisions
* 4 cells formed
* haploid
* genetically different
* pairing of homologous chromosomes form bivalents
* crossing over occurs chiamata formed
* segregation occurs bivalents seperate