D2.1 - cell and nuclear division

Question 1

anucleate

Answer 1

without a nucleus

Question 2

gametogenesis

Answer 2

processes that form gametes

Question 3

homologous chromosomes

Answer 3

chromosomes that contain the same genes at the same loci but different alleles

Question 4

how are new cells in living organisms generated?

Answer 4

a parent cell divides to produce 2 daughter cells

Question 5

mitosis

Answer 5

nuclear division where a mother cell splits into 2 daughter cells and maintains the chromosome number, so they are genetically identical
- involved in asexual reproduction

Question 6

what is mitosis important for?

Answer 6

• growth
• repair
• reproduction
• avoids the production of anucleate cells

Question 7

cytokinesis

Answer 7

splitting of the cytoplasm in a parent cell between daughter cells

Question 8

how does cytokinesis occur in animal cells?

Answer 8

ring of contractile actin and myosin proteins pinches a cell membrane together to form a cleavage furrow which splits the cytoplasm

Question 9

how does cytokinesis occur in plant cells?

Answer 9

vesicles fuse together to assemble sections of the membrane and cell wall to achieve splitting

Question 10

equal cytokinesis

Answer 10

each daughter cell receives half of the components of the parent cell

Question 11

what is needed for unequal cytokinesis to occur?

Answer 11

each daughter cell must receive at least one mitochondrion and one of any other organelle that can only be made by dividing a pre-existing structure

Question 12

what are examples of unequal cytokinesis?

Answer 12

• budding in yeast
• oogenesis in humans, following meiosis

Question 13

meiosis

Answer 13

type of nuclear division where the daughter cells have half the number of chromosomes and creates genetic diversity
- avoids the production of anucleate cells

Question 14

why is DNA replication a prerequisite for both mitosis and meiosis?

Answer 14

• after replication, each chromosome consists of two elongated DNA molecules held together at the centromere
• when these sister chromatids are separated at the anaphase, the chromosome number briefly doubles
• once telophase and cytokinesis have occured, the original number of chromosomes are restored

Question 15

histones

Answer 15

proteins that wrap DNA around themselves to supercoil DNA and condense the chromosomes

Question 16

spindle fibres

Answer 16

long strands of microtubules that are produced by the centrosome
- lengthened or shortened by changing the number of microtubules subunits

Question 17

astral microtubules

Answer 17

contribute to separating the poles of the cell

Question 18

overlap microtubules

Answer 18

connected in pairs by microtubule motor proteins which are pushed towards the poles

Question 19

kinetochore microtubules

Answer 19

bind to the centromere of chromosomes with each chromatid attached to the microtubules from each pole, causing the chromatids to move to each pole

Question 20

what is the process of mitosis?

Answer 20

1. prophase
2. metaphase
3. anaphase
4. telophase

Question 21

what happens during prophase?

Answer 21

• chromosomes supercoil
• centrosomes move away to the poles and form spindle fibres
• nuclear membrane breaks down

Question 22

what happens during metaphase?

Answer 22

• spindle fibres grow and attach to centromeres
• chromosomes move along the equator

Question 23

what happens during anaphase?

Answer 23

• spindle fibres contract and separate the cetromeres and sister chromatids, moving to opposite poles

Question 24

what happens during telophase?

Answer 24

• nuclear membrane reforms around chromosomes at each pole and form two new nuclei

Question 25

what is the order of the cell cycle?

Answer 25

1. interphase - growth and number of sub-cellular structures double
2. mitosis - cell division
3. cytokinesis - cytoplasm splits and moves apart