Module 6 Fixing issues with DNA replication: 4/05

Question 1

DNA Polymerase has proofreading
capability:

Answer 1

Cleaves the phosphodiester backbone and remove an incorrect nucleotide before adding the next one (exonuclease activity).

Question 2

Telemeres

Answer 2

End of linear chromosome of DNA that protect the chromosome

Question 3

Telemeres over time:

Answer 3

Telemeres get shorter with each round of division, until the chromosomes are so damaged that the cell stops dividing. Necrosis.

Question 4

Telomerase

Answer 4

Catalyzes lengthening of telomeres in eukaryotic germ cells. Restores original length.
* Gives each individual cell a timeline as a result of the fact that telemeres become shorter over time.

Question 5

Germ Cells

Answer 5

• Specialized cells produce gametes
• Telomerase active in sperm and egg cells. Assures gametes have completely copied chromosomes with extended telomerase.
• Telomere length remains constant

Question 6

Somatic Cells

Answer 6

Do not have an active telomerase.
* telomere length decreases gradually during the human life span

Question 7

Mismatch Repair

Answer 7

• incorrectly added base is detected and removed from the newly synthesized strand by nuclease action.
• The gap is filled with the correctly paired base.

Question 8

Nucleotide excision repair

Answer 8

Damaged bases are removed and replaced by
nuclease action.