Inheritance of Sameness (Ch.8)

Question 1

what are the 3 main cellular processes?

Answer 1

1. DNA replication
2. a dynamically changing cytoskeleton
3. cell cycle “checkpoints”

Question 2

what happened if a cell divides too quickly?

Answer 2

the daughter cells may be too small or lacking essential cytoplasm or genetic material

Question 3

what happens if a cell divides too slowly?

Answer 3

the cell may grow inefficiently large or accumulate extra chromosomes

Question 4

what is the main cell division process in prokaryotes? and how many periods are there?

Answer 4

binary fission

- 3 periods (B,C,D)

Question 5

Period B

Answer 5

• replication begins almost at the end of the this period

- cells may grow for sometime before initiating DNA synthesis

Question 6

Period C

Answer 6

chromosomes are replicated and separated to the opposite sides of the cell
- replication is continuous

Question 7

Period D

Answer 7

• cell division begins as the plasma membrane grows inwards and a new cell wall is synthesized
• membrane pinches together between them and 2 new daughter cells

Question 8

What happens if a prokaryotic cell has a lot of nutrients?

Answer 8

• the cell will skip Period B since they can grow quickly enough to divide their cytoplasm as soon as DNA replication is complete and chromosomes are separated
• this means that some bacterias can produce new generations quickly (sometimes in 20mins)

Question 9

What is the Segregation theory and why was it proven to be wrong? and Who came up w it?

Answer 9

• Francois Jacob
• bacterial chromosomes of the daughter cells in which the 2 chromosomes are attached to the plasma membrane near the middle of the cell and separate as the new plasma membrane is added between the 2 sites during cell elongation. it is predicted that chromosome segregation is passive
• this is WRONG because it is active and independent from cell elongation

Question 10

what is the difference between prokaryotic cells and eukaryotic cells when it comes to receiving genetic information?

Answer 10

• prokaryotic cells can complete their genetic information If it only receives one copy of a chromosome this would be LETHAL in an eukaryotic cell

Question 11

ploidy

Answer 11

number of chromosomes in a set
(2n = diploid)
(n = haploid)
seedless fruit are TRIPLOID

Question 12

sister chromatid

Answer 12

duplication of each chromosome (before cell division) produces 2 identical copies of each chromosome

Question 13

What does DNA replication involve?

Answer 13

1. replicating the DNA molecule and its what it contains

2. doubling the proteins that are bound to the DNA to stabilize it

Question 14

chromosome segregation

Answer 14

equal distribution of daughter chromosomes into each of the 2 daughter cells that result from cell division

Question 15

Interphase

Answer 15

• longest phase and composed of 3 phases

Question 16

G1 phase

Answer 16

cell carries out its function sonf in some cases grow (varies in length)

Question 17

S phase

Answer 17

DNA replication and chromosome and chromosome duplication occur

Question 18

G2 phase

Answer 18

brieft gain cell cycle in which cell growth continues and cells prepare for mitosis and cytokinesis

Question 19

Prophase

Answer 19

• chromosome begin to condense into rod-like structures (more successful for mitosis)
• while condensation is occurring, the nucleolus becomes smaller and eventually disappears (nuclear envelope disappear) – this means that all types of RNA synthesis is shut down
• in the cytoplasm, mitotic spindle begins to form at the 2 centrosomes as they start migrating towards the opposite ends of the cell to form the spindle poles
• spindle forms as microtubules radiate from the spindle pole

Question 20

Prometaphase

Answer 20

• bundles of spindle microtubule grow from the opposing poles, some attache directly to the chromosome
• Kinetochore has formed (proteins) and attach to the centromere
  (these connections determine the outcome of mitosis bc they attach directly to the sister chromatids of each chromosome to microtubules leading to opposite poles)

Question 21

Metaphase

Answer 21

• spindle reaches its final form and spindle microtubules move the chromosomes into alignment at the spindle midpoint (metaphase plate)
• • only when they are at the midpoint, each sister chromatid is attached to the microtubule leading in opposite directions can metaphase actually take place

Question 22

Karyotype

Answer 22

complete collection of metaphase chromosomes arranged according to size and shape

Question 23

Anaphase

Answer 23

• sister chromatids separate and move to opposite spindle poles
• first sign of movement can be seen at the centromeres as the kinetochores are the first to move towards opposite poles
• separated chromatids are now called daughter chromosomes
• when movement has reached opposite poles, chromosome segregation is complete

Question 24

Telophase

Answer 24

• spindles disassemble and chromosomes at each pole decondense and return to the extended state typical of interphase
• nucleolus reappears and RNA transcription occurs
• new nuclear envelope forms around chromosomes at each pole, producing the 2 daughter nuclei

Question 25

Cytokinesis

Answer 25

division of cytoplasm follows nuclear division stage of mitosis - begins either during telophase or late anaphase - by the time it is complete, the daughter cells have entered the G1 phase of interphase - animals, protist and most fungi -- FURROWING - plants -- CELL PLATE FORMATION

Question 26

Furrowing

Answer 26

- powered by the motor proteins, the microfilaments slide together to tighten the band and constrict the cell - constriction forms a groove (furrow) in the plasma membrane - gradually deepens until the daughter cells are completely separated (same time other organelles/structures approximately equally)

Question 27

Cell plate formation

Answer 27

- layer of microtubules that persists at the former spindle midpoints serve as an organization site for vesicles produced by the ER and Golgi bodies - during expansion of the vesicles, they fuse together and their contents assemble into a new cell wall

Question 28

mitotic spindle formation and action

Answer 28

- central to both mitosis and cytokinesis - made up of microtubules and their proteins, and their activity depends on their changing patterns of organization during cell cycle - major part of the interphase cytoskeleton of eukaryotic cells - occur whether or not there are centromeres present

Question 29

microtubule organization centre (MTOC)

Answer 29

located on the centrosome which is a site from which the microtubules radiate outward

Question 30

Centrioles

Answer 30

- some chromosomes contain them - their main function is generating the microtubules needed for flagella or cilia * *no centrosomes or centrioles are found in angiosperms (flowering plants) and in most gymnosperms (conifers)

Question 31

how mitotic spindles move

Answer 31

2 groups: 1. kinetochore microtubule - connect chromosomes to the spindle poles 2. non-kinetochore microtubules - extend between the spindle poles without connecting to the chromosome - separation at anaphase occurs due to a combo of separate but coordinated movements from both groups - chromosomes "walk" themselves to the poles along stationary microtubules using motor proteins in kinetochore - another method of movement is when the spindle poles pull kinetochore microtubules poleward - non kinetochore movement: push the poles apart by growing in length as they slide

Question 32

Checkpoints - what controls it and how and many are there?

Answer 32

cyclins: are the protein that monitors the progress of the cell - 3 check points

Question 33

G1/S checkpoint

Answer 33

- main checkpoint that determines if a cell is proper - looks for damages in the DNA (ie. radiation chemicals) and also looks for extracellular signals for growth and division

Question 34

G2/M checkpoint

Answer 34

- if a cell passes this phase it is committed to mitosis | - looks for DNA that was not replicated properly in the S phase or if the DNA is damaged by radiation chemicals

Question 35

Mitotic Spindle checkpoint

Answer 35

- within the M phase before metaphase - asses whether the chromosomes are attached properly to the mitotic spindle so they align correctly to the metaphase plate - essentially there to ensure identical daughter cells are produced (which relies on anaphase which relies on metaphase) - once it goes through anaphase there is no turning back