Mitosis

Question 1

why do we need to replicate our cells?

Answer 1

o Growth
o Repair
o Reproduction (for unicellular organisms; mitosis is reproduction)

Question 2

cells spend how long in mitosis

Answer 2

only about 10% of their life

Question 3

G1

Answer 3

o Cellular growth
o Normal life (making proteins cellular respiration, etc)
o DNA is in the form of chromatin
o Cells spend 90% of their time her

Question 4

S phase

Answer 4

o DNA synthesis
o Replicate the cell’s entire genome
o Cell will now have two copies of genetic info
o Only enter phase is they are going to reproduce

Question 5

G2

Answer 5

o Prepare for mitosis
o Cell may spend a short time or a long time in GW
o Nothing really happens that can be seen under the microscope

Question 6

M

Answer 6

o Mitosis

o Organize the replicated genome so that each daughter cell gets an identical genome to what the parent had in G2

Question 7

Cancer

Answer 7

occurs when mitosis happens too often

Question 8

G1 checkpoint

Answer 8

 Determines if conditions are favorable for cell division and if the DNA is damaged

Question 9

G2 checkpoint

Answer 9

checks for DNA damage

Question 10

Metaphase checkpoint

Answer 10

determines if all chromosomes are attached to the spindle apparatus

Question 11

contact inhibition

Answer 11

o Cells are prevented from replicating if they are in contact with other cells on all sides
o To become a tumor, a cell has to lose its contact inhibition

Question 12

telomeres

Answer 12

o Limit the number of times in the life of a cell that it can undergo mitosis

Question 13

How do we keep DNA organized?

Answer 13

• During interphase (G1, S, G2) the DNA is unwound (Chromatin) it winds up for mitosis
• DNA is wound around proteins and condensed into chromosomes

Question 14

Chromosomes

Answer 14

• Humans have 46 chromosomes
• 23 pairs
• appear as a single strand
• when they have replicated, they have 2 strands joined at the center by a centromere
• in this state, each strand= chromatid
• one chromatid=1 chromosome
• two chromatids combined: 1 chromosome

Question 15

chromatin

Answer 15

unwound DNA

Question 16

chromosome

Answer 16

a unit of condensed DNA that replicates as one

Question 17

chromatid

Answer 17

one of two “sisters”, a replicated chromosome

Question 18

homologous pair

Answer 18

contain the same basic info, with slight differences

Question 19

mitosis overview

Answer 19

• DNA is replicated in S phase
• DNA is organized into chromosomes and carefully arranged within the cell so that one copy of each homologous pair ends up at the far ends of the cell
• The cell can then split at the middle and each new cell will end up with a full genome

Question 20

centrosome

Answer 20

a pole of spindle apparatus, contains centrioles

Question 21

centriole

Answer 21

the anchors of the mitotic spindle determine direction of microtubules

Question 22

kinetochore

Answer 22

proteins that attach sister chromatids to spindle

Question 23

Prophase

Answer 23

• DNA condenses into chromosomes
• Nuclear envelope begins to disappear
• Spindle is beginning to form
• Nucleus is still intact

Question 24

prometaphase

Answer 24

• Nuclear membrane has completely disappeared
• Spindle is fully formed
• Chromosomes attach to spindles

Question 25

metaphase

Answer 25

chromosomes move to the middle of the cell (metaphase plate)

Question 26

anaphase

Answer 26

sister chromatids separate and move to the poles

Question 27

telophase

Answer 27

• A whole cell’s worth of DNA in each of the poles
• DNA begins to de-condense
• Nuclear envelope begins to re-form

Question 28

cytokinesis

Answer 28

plasma membrane begins to pull in

two identical daughter cells

Question 29

cells that don’t undergo mitosis

Answer 29

o	Neurons (when you lose a neuron you can’t replace it)
o	All skeletal muscle cells (have thousands of nuclei; can’t decide which one to use)
o	Red blood cells (don’t have a nucleus)

Question 30

how do viruses reproduce

Answer 30

o Do have a genome

o Manipulate the host cell that they live in to do their replication for them

Question 31

steps for viral reproduction

Answer 31

• A virus cannot reproduce itself=no mitosis
• Viruses are composed of a genetic code (DNA or RNA) enveloped in an outer coat
• It must insert its genetic info into that of its host cell, and trigger the host cell to reproduce
• Needs a host cell to reproduce
• Many viruses trigger “out-of-control” mitosis
• The virus must be able to short-circuit the normal controls of mitosis

Question 32

telomeres

Answer 32

sections of DNA on the end of the chromosomes that gets shorter each time the chromosome replicates

no more telomeres=no more replication

premature telomere shortening has been associated with disease and death

premature aging