Nucleic Acids

Question 1

what are nucleic acids?

Answer 1

large molecules that were discovered in cell nuclei.

Question 2

what are the two types of nucleic acid?

Answer 2

• DNA
• RNA

Question 3

what are the roles of nucelic acids?

Answer 3

• roles in storage
• roles in transfer of genetic information
• roles in the synthesis of polypeptides
• they are the basis for heredity.

Question 4

what elements do nucleic acids contain?

Answer 4

carbon, hydrogen, oxygen, nitrogen, and phosphorus.

Question 5

which monomers form nucleic acids?

Answer 5

nucleotides - linked together in a chain.

Question 6

what are the three components that make up a nucleotide?

Answer 6

• a pentose monosaccharide, containing five carbon atoms.
• a phosphate group
• a nitrogenous base.

Question 7

what is a phosphate group?

Answer 7

an inorganic molecule that is acidic and negatively charged.

Question 8

what is a nitrogenous base?

Answer 8

a complex organic molecule containing one or two carbon rings in its structure as well as a nitrogen.

Question 9

what type of reaction links nucleotides together?

Answer 9

condensation reaction to form a polymer called a polynucleotide.

Question 10

how is a long sugar phosphate backbone formed?

Answer 10

the phosphate group at the fifth carbon of the pentose sugar of one nucleotide forms a covalent bond with the hydroxyl group at the third carbon of the pentose sugar of an adjacent nucelotide. The bonds are called phosphodiester bonds.

Question 11

what type of reaction breaks the phosphodiester bonds to release individual nucleotides?

Answer 11

hydrolysis reaction.

Question 12

what does DNA stand for?

Answer 12

Deoxyribonucleic acid.

Question 13

what is the sugar in DNA?

Answer 13

deoxyribose.

Question 14

what is deoxyribose?

Answer 14

a sugar with one fewer oxygen atoms than ribose.

Question 15

what are the four different DNA nucleotides?

Answer 15

• thymine
• cytosine
• adenine
• guanine

Question 16

what are the two groups that DNA nucelotides can be split into?

Answer 16

• pyrimadines
• purines

Question 17

what are pryimadines?

Answer 17

the smaller bases, which contain single carbon ring structures - thymine and cytosine.

Question 18

what are purines?

Answer 18

the larger bases, which contain double carbon ring structures - adenine and guanine.

Question 19

do purines pair with pyrimadines?

Answer 19

yes.

Question 20

how many hydrogen bonds does thymine and adenine form?

Answer 20

two.

Question 21

how many hydrogen bonds does cytosine and guanine form?

Answer 21

three.

Question 22

how long is a DNA molecule?

Answer 22

it varies in length from a few nucleotides to millions of nucleotides.

Question 23

what forms the DNA double helix?

Answer 23

two strands of polynucleotides coiled into a helix.

Question 24

what holds the two strands of the double helix together?

Answer 24

hydrogen bonds between bases.

Question 25

what is the structure of the strands of the double helix?

Answer 25

they have a phosphate group (5’) at one end and a hydroxyl group (3’) at the other.

Question 26

why are strands described as antiparallel?

Answer 26

the two parallel strands are arranged so that they run in opposite directions.

Question 27

what does the pairing between bases allow DNA to do?

Answer 27

be copied and transcribed - key properties required of the molecule of heredity.

Question 28

what is complementary base pairing?

Answer 28

the idea that A and T always join with each other, and C and G always join together.

Question 29

what causes parallel polynucleotide chains?

Answer 29

a small pyrimidine base always binds to a larger purine base. this arrangement maintains a constant distance between the DNA ‘backbones’, resulting in parallel polynucelotide chains.

Question 30

does DNA have equal amounts of adenine and tymine, and equal amounts of cytosine and guanine.

Answer 30

yes.

Question 31

what is the role of RNA?

Answer 31

plays an essential role in the trasfer of genetic information from DNA to the proteins that make up the enzymes and tissues of the body.

Question 32

how can DNA leave the nucleus?

Answer 32

relatively short section of the long DNA molecule corresponding to a single gene is transcribed into a similarly short mRNA molecule; each individual mRNA is shorter than the whole chromosome of DNA

Question 33

how are RNA nucleotides different to DNA nucleotides?

Answer 33

• pentose sugar is ribose rather than deoxyribose.
• thymine base is replaced with the base uracil.

Question 34

how do RNA nucleotides form polymers?

Answer 34

the formation of phosphodiester bonds in a condensation reaction.

Question 35

what happens after protein synthesis?

Answer 35

RNA molecules are degraded in the cytoplasm. phosphodiester bonds are hydrolysed and RNA nucleotides are released and reused.

Question 36

how can DNA be extracted?

Answer 36

1. grind a sample in a mortal and pestle to break down the cell walls.
2. mix the sample with detergent - this breaks down the cell membrane and releases cell contents into solution.
3. add salt - breaks hydrogen bonds between DNA and water molecules.
4. add protease enzyme - breaks down proteins associated with DNA in the nuclei.
5. add a layer of ethanol on top of the sample - alcohol causes the DNA to precipitate out of solution.
6. the DNA will be seen as white strands forming between the layer of sample and layer of alcohol. The DNa can be picked up by spooling it onto a glass rod.