Unit 3 - DNA organization in Eukaryotes and Prokaryotes

Question 1

Nucleosome

Answer 1

a unit of DNA storage consisting of 8 histones with DNA strands wrapped around them; the DNA around each nucleosome is about 147 nucleotides long

(r further packaged into solenoids)

Question 2

Linkers

Answer 2

stretches of DNA connect one nucleosome to the next. At this level of organization, the strand of chromatin appear like a string of beads

Question 3

Solenoid

Answer 3

a group of 6 nucleosomes (30nm chromatin fibers)

Question 4

Prokaryotic DNA organization

Answer 4

have simple DNA structures
- DNA exists on one primary, often circular, chromosome
- DNA is less tightly bound and more easily accessed by the enzymes and other mols involved in replication

Question 5

Plasmids

Answer 5

r smaller, circular sections of DNA that float throughout cells
- exist in addition to the main chromosome
- can exist in one cell and enter the next

Question 6

Conjugation

Answer 6

• a plasmid can exit one cell and enter another
• plasmid of one bacterium can move into another bacterium and join its genome

Question 7

Phenomena allows 2 things

Answer 7

• a natural variation of bacteria
• researches to insert specific genes into host bacteria

Question 8

Prokaryotes don’t have proteins to help package DNA like Eukaryotes

Answer 8

• unbound by a nuclear membrane and DNA is less tightly bound and more easily accessible by the enzyme and other mol involved in replication

Question 9

Supercoiling

Answer 9

used to protect DNA; continuos twisting of prokaryotic DNA to reduce size

Question 10

Telomeres; DNA loss during replication - DNA polymerase and Oki frags

Answer 10

1) DNA polymerase produces small fragments of DNA (OF) on a lagging stand
2) OF are initially attached to RNA primer

Question 11

Telomeres; DNA loss during replication - problem w OF

Answer 11

the lase OF begins at the last RNA primer position which is located close to but not at the end of the strand

Question 12

Telomeres; DNA loss during replication - problem RNA primers

Answer 12

RNA primers is removed, but since DNA polymerase can not bind to the 5’ end, it leaves that section of DNA uncopied

Question 13

Telomeres; DNA loss during replication - result

Answer 13

DNA is shorter by the amt of uncopied segments

Question 14

Loss of DNA during each cycle or replication problem

Answer 14

causes chromosomes to constantly get shorter and can lead to the loss or damage of important genes

Question 15

Solution to loss of DNA during each cycle

Answer 15

1) to prevent the loss of essential coding regions, non-coding sequences r found at the end of chromosomes know as telomers

Question 16

Telomeres

Answer 16

every time a DNA replication part of the telomeres r lost but the coding regions of DNA r kept intact

Question 17

Telomeres act like caps at the end of chromosomes

Answer 17

protect the DNA from losing valuable coding information during replication

Question 18

other functions of DNA replication and aging (4)

Answer 18

1) help prevent chromosome ends from fusing to other
2) prevent DNA degradation from enzymes called nuclease
3) assists DNA repair
4) many play a role in determining the number of times a cell divides and play a really important role in determining lifespan of an organism

Question 19

Role of Telomeres During Replication

Answer 19

repeating sequence of nucleotides at the end of DNA

Question 20

Base pair code sequence found at end of Human DNA

Answer 20

5’ - TTAGGG - 3’
- repeating 2000 times
- 100 bp lost per replication

Question 21

Cell Senescene

Answer 21

• essential portions of DNA may be lost during subsequent replication
• cells can lose ability to function properly
• may lose ability to grow / metabolize / or divide

Question 22

Biological Clock

Answer 22

telomeres r like a BC because they r counting down the total number of times that a cell can divide; know as the HAYFLICK Limit

Question 23

Hayflick Limit

Answer 23

(total number of times that a normal cell can divide)
- diff in each species
- in humans, cells can divide about 50x
- The length of telomers is not related to how long an individual of the species live.

Question 24

Germ Line Cells

Answer 24

MUST maintain their genetic integrity from parent of offspring (Cannot afford to lose any genetic information)

Question 25

Telomerase

Answer 25

which add more DNA to shortening telomers so some stem cells and white blood cells contain telomerase

Question 26

Telomers in the cell tell us two things

Answer 26

1) the age of the cell
2) how many more times the cell will be able to divide effectievly

Question 27

once hayflick limit is reached

Answer 27

senescence begins, cell function declines, and aging bc more apparent
ie. getting older

Question 28

Cancer

Answer 28

cancerous cells produce the enzyme telomerase in large quantities
- replaces the telomers that r lost during cell division
- cancer cells r able to continue dividing making them effectively immortal