Nucleic acids

Question 1

what are polynucleotides

Answer 1

polymers made from nucleotides

Question 2

give two examples of polynucleotides

Answer 2

DNA, RNA

Question 3

give examples of nucleic acids that aren’t polymers

Answer 3

• ATP/ADP
• NADP+
  -NAD+/FAD

Question 4

describe the structure of a general nucleotide

Answer 4

phosphate group-pentose sugar-nitrogenous base

Question 5

describe the structure of a DNA nucleotide

Answer 5

phosphate group-deoxyribose-nitrogenous base

Question 6

what are the four possible nitrogenous bases of a DNA nucleotide

Answer 6

-thymine
-adenine
-guanine
-cytosine

Question 7

describe the structure of an RNA nucleotide

Answer 7

phosphate group-ribose-nitrogenous base

Question 8

what are the four possible bases of a RNA nucleotide

Answer 8

-adenine
-guanine
-cytosine
-uracil

Question 9

name the complementary base pairs in DNA

Answer 9

thymine+adenine
guanine+cytosine

Question 10

why are DNA/RNA polymers

Answer 10

made from small, soluble, single repeating units called nucleotides. many nucleotides can be bonded together to form the much larger polymers

Question 11

name the bonds between A-T

Answer 11

2 hydrogen bonds between the bases

Question 12

name the bonds between G-C

Answer 12

3 hydrogen bonds between these bases

Question 13

name the structural features of DNA (7)

Answer 13

• polynucleotide (polymer) made from many DNA nucleotides (monomers)
• double stranded helix
• antiparallel strands
• complementary base pairing between the strands/nitrogenous bases
• via hydrogen bonding
• A=T G—C
• nucleotides bonded via strong phosphodiester bonds (forming a sugar-phosphate backbone)

Question 14

what shape are the chromosomes in eukaryotic cells

Answer 14

linear

Question 15

explain the stability of DNA

Answer 15

• hydrogen bonding links the complimentary base pairs
• phosphodiester bonds protect the more chemically reactive nitrogenous base pairs in the helix

Question 16

how does the structure of DNA relate to its function (5)

Answer 16

• it has a stable structure due to the phosphodiester (covalent) bonds and its double stranded helix shape
• double stranded, replication can occur using one strand as a template
• weak hydrogen bonds between complementary base pairs, easy to ‘unzip’/separate strands during replication
• large molecule, can carry lots of information
• complimentary base pairing allows identical copies to be made

Question 17

what is the function of DNA (3)

Answer 17

• hereditary material can be passed on, passing genetic information from generation to generation
• genetic code holds information for synthesising proteins
• molecule separated, exposes sections of code for mRNA (DNA replication)

Question 18

describe the process of DNA replication

Answer 18

• DNA helicase unwinds DNA helix
• breaks the hydrogen bonds separating the two strands
• both strands act as a template for forming new strands
• free, activated DNA nucleotides complimentary base pair via hydrogen bonds
• DNA polymerase forms phosphodiester bonds between the nucleotide monomers
• condensation reaction occurs, using ATP, water is released

Question 19

how are DNA and RNA different based on their pentose sugar

Answer 19

DNA nucleotide contains deoxyribose sugar, RNA nucleotide contains ribose sugar

Question 20

how are DNA and RNA different based on their nitrogenous bases

Answer 20

DNA contains bases adenine, thymine, cytosine and guanine
RNA contains bases adenine, uracil, cytosine and guanine

Question 21

how are DNA and RNA different based on their length

Answer 21

DNA is very long, RNA is relatively short

Question 22

how are DNA and RNA different based on their shape

Answer 22

DNA has a linear, double stranded helix, coiled shape
mRNA has a linear, single stranded shape
rRNA has a bulky with proteins shape
tRNA has a bulky t-shaped shape

Question 23

how are DNA and RNA different based on their cell location

Answer 23

DNA is found in the nucleus
mRNA is found in the nucleus and the cytoplasm
rRNA is found in the cytoplasm attached to the RER
tRNA is found in the cytoplasm attached to amino acids

Question 24

how are DNA and RNA different based on their lifespan

Answer 24

DNA is very stable and has a long lifespan, RNA often breaks down so has a short lifespan

Question 25

how are DNA and RNA different based on their role

Answer 25

DNA is designed to store genetic information and code for building proteins RNA is used for protein synthesis

Question 26

describe step one of meselson and Stahl's experiment on DNA replication

Answer 26

-bacteria are grown in a broth containing the heavy N15 isotope - dna contains nitrogen in its bases - so as the bacteria replicated they used the nitrogen in the broth to make new DNA nucleotides - after some time the culture of bacteria had DNA containing only the heavy N15

Question 27

describe step two of meselson and Stahl's experiment on DNA replication

Answer 27

- DNA from the N15 culture of bacteria was extracted and spun in a centrifuge - it showed dna containing the heavy n15 settled near the bottom of the centrifuge tube

Question 28

describe step three of meselson and Stahl's experiment on DNA replication

Answer 28

- the bacteria containing only N15 dna was taken out of the N15 broth and placed in one of a lighter N14. the bacteria was then left so that one round of DNA replication could occur. their dna was then extracted and spun in a centrifuge - (if conservative dna replication had occurred) - the original template dna molecules would only contain the N15 and settle at the bottom of the tube, and the new dna molecules would only contain the lighter N14 and settle at the top of the tube - (if semi-conservative replication had occurred) - all the dna molecules would contain the N14 and N15 and settle in the middle of the tube the second form of replication occurred and the scientists confirmed that DNA underwent semi-conservative replication

Question 29

what were the three possible forms of dna replication did people research

Answer 29

- semi-conservative (proven) - conservative (disproven) - dispersive replication (disproven)