nucleic acids

Question 1

what is DNA

Answer 1

-polymer made up of monomers called nucleotides

Question 2

what does nucleotide consist of

Answer 2

-in the centre there’s a 5 carbon deoxyribose sugar
-attached to the sugar there’s is a nitrogenous base at C1
-on the other side of the sugar is attached to a negatively charged phosphate group at C4

Question 3

which elements do nucleotides consist of

Answer 3

carbon
hydrogen
oxygen
nitrogen
phosphorus

Question 4

what does a sugar and phosphate group make up

Answer 4

sugar phosphate backbone

Question 5

compare DNA and RNA

Answer 5

DNA
-pentose sugar is called deoxyribose
-this has 1 less oxygen atom (bc of 1 less hydroxide group)

RNA
-pentose sugar is called ribose sugar

Question 6

what are the bases found in DNA

Answer 6

Adenine
Thymine
Guanine
Cytosine

Question 7

what are DNA and RNA

Answer 7

important information carrying molecules

Question 8

what are the bases found in DNA

Answer 8

Adenine -Thymine
Guanine-Cytosine

Question 9

what are purines

Answer 9

bases that have a double ring structure
Adenine and Guanine

Question 10

what are pyrimidines

Answer 10

single ring structures like thymine and Cytosine

Question 11

how does DNA codes affect the function of a protein

Answer 11

DNA codes for the sequence of amino acids on the primary structure of protein which determines the final 3D structure and function of protein

Question 12

what are the bases found in RNA

Answer 12

Adenine-Uracil
Guanine-Cytosine

Question 13

where is the phosphodiester bond formed

Answer 13

between the phosphate group of one nucleotide and the hydroxyl group of the pentose sugar of other nucleotide

Question 14

what happens when a phosphodiester bond forms

Answer 14

water is released

Question 15

how is dna formed

Answer 15

by forming a polymer of nucleotides called a polynucleotide

Question 16

describe the structure of DNA

Answer 16

-it consists of 2 polynucleotide strands

-bases on one strand are complimentary to the other

-purines on one strand always pairs with pyrimidine on opposite strand

-2 strands are anti paralel

-3 bases code for one amino acid (triplet code)

Question 17

describe an mRNA molecule

Answer 17

-short polynucleotide chain
-usually single stranded
-mRNA used to transfer genetic information from DNA to ribosomes

Question 18

what ensures that the 2 strands remain same distance apart

Answer 18

-adenine pairs with thymine
-guanine pairs with cytosine

Question 19

why are the 2 strands in DNA antiparallel

Answer 19

because they run in opposite directions

Question 20

What is the function of a sugar phosphate backbone and double helix structure

Answer 20

• provides strength and stability
  -protects information coded in bases
  -protects hydrogen bonding between bases

Question 21

what is the function of DNA being a large molecule

Answer 21

• stores a lot of information

Question 22

what is the function of the base sequence in DNA

Answer 22

allows information to be stored and codes for amino acids therefore codes for proteins

Question 23

what is the function of dna being double stranded

Answer 23

so that replication can occur semi conservatively because each strand acts as a template

Question 24

what is the function of complementary base pairing

Answer 24

allows accurate replication, so identical copies are made (prevents mutations)

Question 25

what is the function of hydrogen bonding between bases being weak

Answer 25

allows for easy strand separation for semi-conservative replication

Question 26

what is the function of there being many weak hydrogen bonds in DNA

Answer 26

SO DNA is a Strong / stable molecule

Question 27

what does semi conservative replication ensure

Answer 27

Semi-conservative replication ensures that each new DNA molecule contains an original and a new strand and is identical to the original DNA.

Question 28

Function of DNA polymerase

Answer 28

catalyses the condensation reactions between DNA nucleotides to form the sugar-phosphate backbone of the new strand.

Question 29

Function of DNA helicase

Answer 29

breaks the hydrogen bonds between complimentary base pairs so each strand can act as a template.

Question 30

how does semi conservative replication occur

Answer 30

The enzyme DNA Helicase attaches and unwinds the DNA and breaking hydrogen bonds The two strands separate. Each strand acts as a template. New DNA nucleotides attracted to bases that are complementary U-A G-C The enzyme DNA polymerase joins the adjacent nucleotides together in a 5’ to 3’ direction.

Question 31

why does DNA polymerase only act in a 5’ to 3’ direction.

Answer 31

DNA polymerase has a specific active site, only complementary to the 5’ end of the incoming free DNA nucleotide and the 3’ end of the developing strand.

Question 32

what where the other 2 theories for the replication of DNA

Answer 32

Dispersive Model – New molecules are made of segments of new and old DNA. Conservative Model – An entirely new molecule is synthesized from a DNA template (which remains unaltered).

Question 33

who designed an experiment to determine the correct theories for DNA replication

Answer 33

Meselson and Stahl

Question 34

describe the Meselson and Stahl experiment

Answer 34

They began by growing E. coli in medium, containing a "heavy" isotope of nitrogen. Then the DNA strands will be spun in a centrifuge to confirm density, N15 will form a band near the bottom. This generation will be 100% N15 containing Bacteria is grown in medium with N14 and 100% DNA is N14 and N15