dna (test 3)

Question 1

DNA structure

Answer 1

• composed of nucleotide monomers
• deoxyribose sugar, phosphate groups, nitrogen-containing base

Question 2

purines

Answer 2

adenine, guanine
- double ring

Question 3

pyrimidines

Answer 3

thymine, cytosine
- single ring

Question 4

dna discovery

Answer 4

• double helix structure discovered in 1950s
• erwin chargaff, james watson, francis crick, rosalind franklin

Question 5

dna bonds

Answer 5

• hydrogen bonds connect complementary dna strands (AT, GC)
• covalent bonds link the deoxyribose of one nucleotide to the phosphate group of the next

Question 6

dna strand sequence

Answer 6

• 2 strands are complementary
• run antiparallel

Question 7

chromosomes

Answer 7

• single long dna double helix wrapped around proteins
• humans have 23 pairs (46 total)
• autosomes (22 pairs), chromosomes (1 pair)

Question 8

dna replication

Answer 8

helicase:
- enzymes unwind double helix
- each strand remains intact

dna polymerase:
- enzyme starts base pairing sequence

dna ligase:
- fixes breaks in p-backbone

Question 9

directional synthesis

Answer 9

• last carbon atom on one end of the strand is a 5’ carbon of a sugar
• last carbon atom on the other end is a 3’ carbon
• dna polymerase can only attach a nucleotide to a 3’ end

Question 10

mutations

Answer 10

• permanent change in the dna sequence of a chromosome
• can be caused by uv radiation or carcinogen exposure
• eukaryotic polymerases add ~50 nucleotides per second, mistakes are inevitable
• introduce genetic diversity