LECTURE 15

Question 1

What do the signals that control cell division for eukaryotes related to?

Answer 1

The function of the entire organism, not the individual cell.

Question 2

Do eukaryotes of multiple origins and if so, why?

Answer 2

Yes, because their chromosomes are very long

Question 3

Why is eukaryotes DNA segregation more complicates then prokaryotes

Answer 3

• nuclear envelope
• multiple chromosomes
• each chromosome can be very long

Question 4

Replicated DNA molecules becomes very ___________ in the __________ before they segregate in eukaryotes

Answer 4

Condensed Nucleus

Question 5

Chromatin

Answer 5

A complex of DNA and proteins that are the building materials for chromosomes

Question 6

Sister chromatids

Answer 6

Two copies of replicated DNA that are connected to each other

Question 7

Centromere

Answer 7

A physical construction of the duplicated chromosome. Sister chromatids attach at this site.

Question 8

Eukaryotes cytokinesis

Answer 8

• division of cytoplasm
• final stage of cell reproduction
• different in plant and animals cells

Question 9

Do the number of chrome men’s correlate with the complexity of the organism ?

Answer 9

NO

Question 10

Each chromosomes form each parent are closely matched in :

Answer 10

• physical appearance

- genetic info content (NOT identical)

Question 11

All parts of interphase

Answer 11

M = mitotic phase 
G1 = Gap phase 
S = DNA synthesis phase 
G2 = Gap 2 phase

Question 12

Interphase

Answer 12

• chromosomes present but NOT visible

- metabolic activity and growth occur, control decisions to grow.

Question 13

G1 phase

Answer 13

Prepares the cell for DNA replication by growing in size.

Question 14

Start of S phase

Answer 14

DNA replication when the two strands of helix unwind (starting at the origin)

• each serves as a template for synthesis of a new strand

REPLICATION OF DNA

Question 15

End of S phase

Answer 15

Each chromosome (there are 2) consists of one old strand and one new strand

• chromatids are tight to associated at Centro mere region

Question 16

G2 phase

Answer 16

cell prepares for chromes segregation and cell division

• centrioles duplicate (new one (daughter centriole, d) grows out of the older centriole (mother centriole, m))
• Nucleolus visible
• chromes duplicated but NOT condensed

Question 17

When do centriole duplicate

Answer 17

G2

Question 18

Prophase

Answer 18

The two centrosomes gets in to separate.

• nucleoli disappear
• chromatin fibbers becomes more condensed and visible
• sister chromatids visible
• centrosome visible

Question 19

Why do the centrosomes separate in prophase

Answer 19

because of microtubule growth and motor proteins pushing against opposite microtubules

Question 20

Prometaphase

Answer 20

Nuclear envelope begins to breakdown.

• kinetochores grab onto microtubules and holds on the end of microtubules
• microtubules grow and shrink

Question 21

How does the nuclear envelope breakdown in prometaphase ?

Answer 21

Liam is disassemble, and membrane forms small vesicles that remain around the chromosomes

Question 22

What does the breakdown fo the nuclear envelope during prometaphase allow?

Answer 22

Allows microtubules to grow into the area and make contact with kinetochores

Question 23

Kinetochores

Answer 23

Each chromatid has ONE kinetochore; the pair face in the opposites directions. The kinetochores captures microtubules and is required for proper chromosome congregation and separation of sister chromatids.

Question 24

What are kinetochores made of ?

Answer 24

Larger structure made of many types of proteins.

Question 25

Where doe kinetchore protujens assemble on ?

Answer 25

They assemble on the centromeric DNA

Question 26

What holds chromatids together

Answer 26

Cohesins

Question 27

Cohesins

Answer 27

Special protein complexes that hold chromatids together

Question 28

Do cohesins remain intact during anaphase?

Answer 28

YES

Question 29

When all chromosomes are at the met phase splats and properly attached to microtubules, a signal is sent that results in...

Answer 29

A part of cohesins getting destines by protease called separase. This opens the ring, along the sister chromatids to separate.

Question 30

Before anaphase a protector protein (called _____) prevents the _________ of cohesins

Answer 30

Securin. Destruction

Question 31

At the start of anaphase, securin gets destroyed by a protein degration machine called the

Answer 31

Anaphase-promoting complex Or APC

Question 32

Loss of securin results in the

Answer 32

Cohesin ring opening up or breaking apart

Question 33

Anaphase

Answer 33

- shortest stage - begins when cohesin protests are cleaved - tensions builds due to kinetochore microtubules pulling equally in opposite directions - this tensions released and chromatids move rapidly apart, with kinetochore leading away

Question 34

Mitotic chromatid segregation can occur by two different events:

Answer 34

1) short eating the distance between poles and chromatids (anaphase A) 2) movement of spindle poles (chromosomes) apart (anaphase B) Cell may use either or both of these methods

Question 35

Telophase

Answer 35

- Two daughter nuclei form in cell - nuclear envelope start to reform - chromosomes start to de-condense - spindle microtubules depolymerize - nucleoli reappear - results in 2 identical daughter cells

Question 36

Plant mitotic spindles

Answer 36

- sue chromatin (not centrosomes) to uncleared microtubules | - spindle assembles in an “inside-out” fashion

Question 37

Some animal cells and many female meiotic spindles assemble

Answer 37

Without centrioles

Question 38

Mitotic spindles in prometaphase

Answer 38

Microtubules start to form around the chromatin as soon as nuclear envelop starts to break down

Question 39

Mitotic spindles in metaphase

Answer 39

Kinetochore-microtubules form alongside non-kinetochore microtubules (bipolar spindles forms)

Question 40

Mitotic spindles in anaphase and telophase

Answer 40

Microtubules become cross linked (microtubule motor proteins involved) - this proved stable structure for chromatid segregation