3.4 DNA Replication

Question 1

Conservative model of replication

Answer 1

Original strands of DNA pair with each other again after being used as a template for replication

Question 2

Semi-conservative model of replication

Answer 2

The two parental strands of DNA serve as a template for a complimentary strands

Each double helix of DNA contains one DNA strand from the parent and one newly synthesized DNA strand

Question 3

Dispersive model of replication

Answer 3

Fragments of parental and newly synthesized DNA would be present in both copies of the DNA

Question 4

Meselson-stahl experiment

Answer 4

Used isotope nitrogen 15 to show that DNA is semi-conservative. E coli with the heavier DNA containing N15 was placed in media with N14 and after replication the DNA had a weight between the N15 and N14 DNA. Further replication in N14 media created less of the combined N15 and N14 DNA and more N14 only DNA.

Question 5

Helicases

Answer 5

Break hydrogen bonds between base pairs

Question 6

Topoisomerases

Answer 6

Surround unzipped strands of DNA and relax the twisting of the helices

Question 7

Primase

Answer 7

Builds short stretches of RNA called primers

Question 8

Primers

Answer 8

Start elongation

Question 9

DNA polymerase

Answer 9

Travels down the DNA strand during elongation starting at the RNA primer and adds new nucleotides in the 5’ to 3’ direction

Question 10

Ligase

Answer 10

Puts Okazaki fragments together to form a complete daughter DNA molecule

Question 11

Binary fission

Answer 11

Mechanism by which prokaryotic cells divide

Question 12

Termination

Answer 12

RNA primers removed and replaced with DNA and ligase completes the sugar-phosphate backbone at nicks in newly synthesized DNA. Newly synthesized DNA is also checked for mistakes.

Question 13

Start codon

Answer 13

The codon for methionine that instructs the ribosome to begin fabricating an amino acid chain

Question 14

Stop codon

Answer 14

Tells ribosomes to stop adding amino acids

Question 15

Large-scale mutations

Answer 15

Happen during meiosis due to damaging agents such as radiation or exposure to teratogens during developmental phases

Frequently result in lethal conditions but some only change phenotype

Four types: deletion, duplication, inversion, translocation

Question 16

Deletion

Answer 16

A segment of DNA is lost

Question 17

Duplication

Answer 17

A segment is duplicated and inserted back into the original DNA

Question 18

Inversion

Answer 18

A segment of DNA is reversed

Question 19

Translocation

Answer 19

A segment of DNA is moved to another homologous chromosome

Question 20

Small-scale mutations

Answer 20

Primarily affect protein synthesis

Question 21

Silent mutation

Answer 21

Single base is changed but the amino acid coded does not change

Question 22

Missense mutation

Answer 22

Single base is changed and codes for a different amino acid as a result

Question 23

Nonsense mutation

Answer 23

A single base is changed which results in a STOP codon

Question 24

Frame shift mutation

Answer 24

Single base deletion or insertion causes a shift in the reading frame which in turn changes the amino acid sequence

Question 25

Germline mutations

Answer 25

Inherited from a parent, originate from sperm or egg. Offspring will have mutation in every cell.

Question 26

Acquired mutation

Answer 26

Aka somatic mutation

Caused by environmental exposure to mutagens. Cannot be passed on to offspring.

Question 27

Mutagens

Answer 27

Any agent that causes genetic mutations such as uv light, radio active compounds, X-rays, chemicals.