DNA structure, replication

Question 1

What is DNA?

Answer 1

Double helix; can be described as a twisted leader with rigid rungs

Question 2

Of what is backbone or the side made of?

Answer 2

Sugarphosphate components, whereas the rungs are made up of pairs on nitrogenous base

Question 3

From what is a single nucleotide made?

Answer 3

It’s composed of sugar (deoxyribose) attached to phosphate and a nitrogen base

Question 4

Nitrogenous bases of DNA

Answer 4

ADENINE + THYMINE

GUANINE + CYTOSINE

Question 5

Antiparallel

Answer 5

Nucleic acid strands are always antiparallel, whether they are DNA/DNA or DNA/RNA or RNA/RNA interactions

Question 6

What is DNA replication?

Answer 6

The making of DNA from the existing DNA strand

Question 7

What is semiconservative?

Answer 7

DNA replication

Question 8

What does semiconservative mean?

Answer 8

That at the end of replication, each of the daughter molecules has one old strand, derived from the parent strand of DNA, and one stran that is newly synthesized.

Question 9

Six major points in DNA replication

Answer 9

1. It begins at sites called the origins of the replication
2. Initiation proteins bind to the origin of the replication and separate the two strands, forming a replication bubble. DNA replication then proceeds in both directions along the DNA strand until the molecule is copied.
3. Enzymes - DNA polymerases catalyze the elongation of new DNA at the replication fork
4. DNA polymerase adds nucleotides to the growing chain one by one
5. DNA is antiparallel. Leading strand - DNA replication. Lagging strand - this one turns the other way
6. The lagging strand is synthesized in separate pieces called Okazaki fragments, they are sealed together by DNA ligase, forming a continuous DNA strand.

Question 10

What does mismatch repair mean?

Answer 10

Special repair enzymes fix incorrectly paired nucleotides

Question 11

What does nucleotide excision repair mean?

Answer 11

Incorrectly placed nucleotides are excised or removed by enzymes termed nucleases, and the gap left over is filled with the correct nucleotides

Question 12

How to avoids losing the terminal gene?

Answer 12

The linear ends of eukaryotic chromosomes are capped with telomeres - short repetitive nucleotide sequences that do not contain genes.

Question 13

Bacterial chromosome

Answer 13

Is a double-stranded, circular DNA molecule associated with a small amount of protein

Question 14

Eukaryotic chromosome

Answer 14

Are linear DNA molecules associated with large amounts of protein

Question 15

What are DNA and protein packed together in eukaryotic cells?

Answer 15

Chromatin

Question 16

What happens when DNA becomes more highly packed?

Answer 16

It becomes less accessible to transcription enzymes, which reduces gene expression.

Question 17

Euchromatin

Answer 17

The less condensed form of eukaryotic chromatin that is available for transcription

Question 18

Heterochromatin

Answer 18

Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed