DNA structure and replication

Question 1

What must genetic material do?

Answer 1

Contain complex info, replicate faithfully, encode phenotype, vary

Question 2

What are DNA nucleotides made of?

Answer 2

Deoxyribose sugar, phosphate group, nitrogenous base (A, T, C, G)

Question 3

What bonds hold nucleotides together in DNA?

Answer 3

Phosphodiester bonds link sugars and phosphates; hydrogen bonds hold complementary bases

Question 4

What is DNA polarity?

Answer 4

Strands run antiparallel (5’ to 3’ and 3’ to 5’)

Question 5

Difference between DNA and RNA sugars and bases?

Answer 5

DNA has deoxyribose and T; RNA has ribose and U

Question 6

How is DNA packaged in eukaryotes?

Answer 6

Wrapped around histones forming nucleosomes, then condensed into chromatin and chromosomes

Question 7

What are histones rich in?

Answer 7

Positively charged amino acids (lysine, arginine) that bind DNA’s negative backbone

Question 8

What is semiconservative DNA replication?

Answer 8

Each new DNA has one original and one new strand

Question 9

How are leading and lagging strands synthesized?

Answer 9

Leading strand continuously (3’ end toward fork); lagging strand in Okazaki fragments (3’ end away)

Question 10

What enzymes are key in replication?

Answer 10

RNA primase, DNA polymerase, DNA ligase

Question 11

What is proofreading in replication?

Answer 11

DNA polymerase corrects errors by removing mismatched base

Question 12

What problem occurs during chromosome replication?

Answer 12

Lagging strand shortening leads to loss of DNA ends

Question 13

How is DNA end shortening solved?

Answer 13

Telomeres—repetitive sequences at chromosome ends

Question 14

How does prokaryotic cell division occur?

Answer 14

Binary fission with circular DNA replication and membrane synthesis

Question 15

What are the main phases of the eukaryotic cell cycle?

Answer 15

M phase (mitosis), Interphase (G1, S, G2), and sometimes G0 (non-dividing)

Question 16

What happens during S phase?

Answer 16

DNA replication

Question 17

What are sister chromatids?

Answer 17

Identical DNA copies held together at the centromere

Question 18

Outline the stages of mitosis

Answer 18

Prophase (chromosomes condense), Prometaphase (spindle attaches), Metaphase (chromosomes align), Anaphase (chromatids separate), Telophase (nuclear envelope reforms), Cytokinesis (cell divides)

Question 19

What are kinetochores?

Answer 19

Protein complexes at centromeres that attach chromatids to spindle microtubules