15 Replication Bio

Question 1

DNA replication begins at

Answer 1

Replication Origins

Eukaryotes have multiple, prokaryotes have single.

Question 2

Replication fork

Answer 2

Y shaped regions where parental DNA strands are being unwound. Semi conservative.

Question 3

DNA helicases

Answer 3

Enzymes untwist the helix at replication forks to allow them to be available as templates.
Unpaired DNA strands are stabilized by single strand binding proteins.
Topoisomerases help to relieve strain in double helixes.

Question 4

Initial nucleotide chain

Answer 4

Is actually a small RNA stretch. RNA primer uses the enzyme primase. About 5-10 nucleotides long and base pairs with DNA.

Question 5

Antiparallel

Answer 5

The two DNA strands are not the same but run in opposite directions. 5’ to 3’. One strands is made in continuous fashion while the other is discontinuous (lagging strand).

Question 6

DNA Polymerase III

Answer 6

Leading strand 5’ to 3’

Question 7

Okazaki fragments

Answer 7

Lagging strands, discontinuous. 3’ to 5’

Question 8

DNA polymerase I

Answer 8

removes the RNA nucleotides of the primer and replaces them at the 3’ end of adjacnet Okazaki fragments.

Question 9

Okazaki fragments are joined into continuous span by

Answer 9

DNA ligase

Question 10

Telomeres

Answer 10

Nucleotide loss at the end of chromosome ends. Have no genes, multiple repetitions. Functions to protect the genes.

Question 11

Telomerase

Answer 11

Enzyme catalyzes the lengthening of the telomeres and restores them.
Reverse transcriptase enzyme that carries its own RNA.

Question 12

Cancer and telomerase

Answer 12

High levels of telomerase activity is shown in human cancer cells. Cancer cells escape cell death due to chromosomal shortening like most somatic cells.