DNA Structure

Question 1

what is DNA

Answer 1

• a type of nucleic acid
• a macromolecule containing genetic info
• in eukaryotic cells it is found in the nucleus
• in prokaryotic cells it is found in the cytoplasm

Question 2

what are nucleic acids

Answer 2

polymers

Question 3

what are DNA monomers called

Answer 3

• nucleotides
• many monomers bonded together are called polynucleotide

Question 4

what are nucleotides made of

Answer 4

1. a phosphate group
2. pentose sugar
3. a nitrogenous base

Question 5

what are the two types of pentose sugars

Answer 5

• deoxyribose (missing an O2 atom)
• ribose (has missing O2 atom)

Question 6

how many nitrogenous bases are there and what are they called

Answer 6

• 4 types
• adenine bonds to thymine
• guanine bonds to cytosine

Question 7

what is the phosphodiester bonds

Answer 7

the phosphate group bonded to the pentose sugar

Question 8

what does the phosphodiester bond create

Answer 8

a sugar-phosphate backbone

Question 9

how are polynucleotides read

Answer 9

read from 5’ to 3’

Question 10

DNA polymers

Answer 10

• double stranded
• two strands are antiparallel and complementary

Question 11

what are the two strands held together by

Answer 11

• hydrogen bonds which forms the double helix shape
• hydrogen bond holds the two strands together like a zipper

Question 12

what does antiparallel mean

Answer 12

• one strand of the backbone runs from 5’ - 3’
• second stand runs from 3’ - 5’

Question 13

what does complementary mean

Answer 13

• nitrogenous bases on one strand are complementary to bases on the other strand

Question 14

how many bonds does each nitrogenous base form

Answer 14

• adenine forms 2 hydrogen bonds with thymine
• guanine forms 3 hydrogen bonds with cytosine

Question 15

how is the double helix formed

Answer 15

• phosphodiester bonds form backbone of the DNA ladder
• hydrogen bonds are the rungs of the ladder
• when it is twisted it forms the double helix shape

Question 16

how does polynucleotide become chromosome

Answer 16

• DNA double helix coils around proteins called histones to form nucleosomes
• DNA is called chromatin at this point
• chromatin coils and supercoils to form a chromosome

Question 17

how does one chromosome form

Answer 17

• double helix condenses to form a single chromosome (unduplicated)
• chromatid replicates (during S-phase of interphase) to form sister chromatid
• still one chromosome but is duplicated
• splits during mitosis and one chromatid goes to each daughter cell