6.5 and 6.6: DNA Organization + DNA Replication and Aging

Question 1

histones

Answer 1

special protein molecule that is the core the DNA strand wraps around
- positively charged proteins and negatively charged DNA strands are attracted to them
- attraction causes DNA to wrap around cluster of 8 histones

Question 2

nucleosomes

Answer 2

units of DNA storage consisting of 8 histones with DNA wrapped around; DNA around nucleosome is 147 nucleosides long

Question 3

solenoids

Answer 3

further DNA packing done by coiling strings of nucleosomes in cylindrical fibres; group of 6 nucleosomes

Question 4

if DNA has active genes?

Answer 4

nucleosomes adapt for gene expression proteins and enzymes to access coding sequence of bases

Question 5

if DNA has inactive genes?

Answer 5

solenoids work as storage units that protect DNA from damage

Question 6

bacterial DNA

Answer 6

consists of one chromosome usually circular and since unbound to nuclear membrane DNA is looser and more easily accessed by enzymes and other molecules in replication

Question 7

conjugation

Answer 7

plasmids can exit one cell and enter another; when 2 bacteria are close together a plasmid in one bacterium can pass into another and the recipient incorporates new plasmid in its genome

Question 8

supercoiling

Answer 8

continuous twisting of prokaryotic DNA that reduces volume of DNA; used when packing DNA in small cell

Question 9

telomeres

Answer 9

repeating sequence of DNA at end of chromosome protecting coding regions from being lost during replication

Question 10

What are the functions of telomeres?

Answer 10

• prevent chromosome ends from fusing to other chromosomes
• prevent DNA degradation from enzymes called nucleases
• assist DNA repair mechanisms in distinguishing DNA breaks from chromosomal ends
• may help in determining number of times cell divides, therefore determining lifespan of organism

Question 11

cell senescence

Answer 11

period in a cell’s life where cell loses ability to divide and grow; aka cell aging

Question 12

hayflick limit

Answer 12

total number of times that a normal cell can divide

Question 13

telomerase

Answer 13

enzyme that adds new telomere sequences to ends of chromosomes; STEM cells and WBCs and germ line cells have telomerase

Question 14

Telomeres and Aging

Answer 14

• once cell reaches hayflick limit and senescence, cell’s functioning decline
• as organism ages, more cells reach senescence, difficult for healthy cells to function at their best

Question 15

Telomeres and Cancer

Answer 15

• cancer cells never stop dividing so telomerase replaces telomeres that are lost during cell replication
• decreasing telomere length in cancer cells may act as prevention bc might cause cells to die naturally before cancer mutation