DNA

Question 1

Whats DNA

Answer 1

Made up of nucleotides, building up a sugar phosphate backbone in a double helix structure.

Question 2

Whats a nucleotide made up of?

Answer 2

A phosphate group, nitrogenous bases and a pentose sugar.

Question 3

What bonds the nitrogenous bases and the pentose sugar in a nucleotide

Answer 3

Glycosidic bond

Question 4

What bonds a phosphate group and the pentose sugar in a nucleotide

Answer 4

Phospodiester bond

Question 5

Whats the nitrogenous bases of DNA

Answer 5

A+T and C+G

Question 6

What are the purines

Answer 6

A and G, this means that they are made up of two rings.

Question 7

What are pyridines?

Answer 7

Made up of 1 ring. C,T,U are all a part of

Question 8

What bonds are between A and T

Answer 8

There are 2 hydrogen bonds

Question 9

What bonds are between C and G

Answer 9

There are 3 hydrogen bonds

Question 10

Whats the sugar called in DNA?

Answer 10

Deoxyribose

Question 11

Whats the sugar called in RNA?

Answer 11

Ribose

Question 12

Whats the 3 types of RNA

Answer 12

mRNA - messenger
tRNA - transfer
rRNA - ribosomal

Question 13

Whats the actual names for A,T,C,G and U

Answer 13

A = Adenine
T = Thymine
G = Guanine
C = Cytosine
U = Uracil

Question 14

How’s the structure of RNA different to DNA?

Answer 14

The pentose sugar is called ribose rather than deoxyribose. The bases are also A+U and C+G, the difference being the U instead of T

Question 15

Who made the discovery of the DNA

Answer 15

Wilkins, Crick, Watson and Franklin

Question 16

Whats an allele

Answer 16

A type of gene that codes for a specific thing

Question 17

Whats a gene

Answer 17

A section of DNA

Question 18

How are nucleotides formed?

Answer 18

Condensation reactions, these also produce a water

Question 19

How can you breakdown nucleotides

Answer 19

Adding water, this reaction is called a hydrolysis reaction.

Question 20

Whats the name for DNA replication?

Answer 20

Semi - conservative

Question 21

Explain DNA replication step by step from the DNA in a double helix to the 2 semi conservative strands.

Answer 21

1. In semi-conservative DNA replication it begins with the strand of DNA in a double helix structure. This double helix unwinds with the enzyme gyrase catalysing the reaction.
2. The enzyme helicase breaks hydrogen bonds between complementary base pairs on the 2 strands of DNA. These are now called template strands.
3. Then activated nucleotides (nucleotides with 3 phosphate groups) from the nucleoplasm join their adjacent complementary bases and form hydrogen bonds.
4. Then DNA polymerase forms new phosphodiester bonds between the phosphate group and the sugar in the nucleotides of the new strands. One of the sets is leading and will form one after the other in the direction DNA polymerase functions. The other strand is called lagging which forms Okazaki fragments which are then joined together with ligase.
5. These 2 new DNA strands twist into a double helix, with one old strand and one new strand. This is called semi-conservative DNA replication.

Question 22

Explain how the theories of DNA replication were researched

Answer 22

By using nitrogen isotopes.In the first generation, the bacteria was grown in the heavy isotope. This shows one line at the bottom of the test tube.
In the second generation, the bacteria was grown in the light isotope. This resulted in one line in the middle of the test tube, showing each DNA double helix were mixed, this proved that conservative was false.
Next, they grew the bacteria in the light isotope again. This resulted in one line at the top and one line in the middle of the test tube. This disproved the dispersive model as if it was true then there would still only be one line. This overall experiment led to the confirmation of semi-conservative model

Question 23

Whats gyrase

Answer 23

The enzyme that breaks untwists the DNA double helix in transcription and replication of DNA

Question 24

Whyd they use nitrogen isotopes in DNA replication theory experiments?

Answer 24

Because the bases of DNA are made of nitrogen

Question 25

Whats helicase?

Answer 25

The enzyme that breaks hydrogen bonds in DNA replication and transcription

Question 26

Whats the differences in RNA and DNA

Answer 26

DNA has deoxyribose sugar, RNA has a ribose sugar. DNA has bases ATCG, RNA has bases AUCG. Theres only one type of DNA and 3 type of RNA.

Question 27

Whats produced in transcription?

Answer 27

mRNA and the original DNA double helix

Question 28

Whats an intron and exon?

Answer 28

An intron is a non coding part of a gene. An exon does code. Introns are cut out of mRNA

Question 28

Explain transcription

Answer 28

1. Gyrase untwists the part of the DNA double helix that contains the particular desired gene. 2. Helicase breaks the hydrogen bonds between the nitrogenous bases, separating the 2 strands. 3. Activated RNA nucleotides come along and attach to their complimentary bases. They attach to the template strand, they’re similar to the coding strand other than their replacement of T to U 4. These form temporary hydrogen bonds between the template strand and the mRNA. 5. RNA polymerase forms a new sugar phosphate backbone of the mRNA between the phosphate group and ribose sugar. 6. The hydrogen bonds then break between the template strand and the mRNA, this occurs alongside splicing in which introns are cut out of the mRNA as they do not code for the desired gene. This leaves the mRNA composed of exons. 7. The original 2 DNA strands rewind to form their double helix whilst the mRNA exits the nucleus towards a ribosome.

Question 29

Whats a triplet?

Answer 29

Each 3 bases of DNA

Question 30

Whats a codon

Answer 30

Each 3 bases of mRNA, each codon codes for an amino acid

Question 32

Explain step by step translation

Answer 32

1. Transcription takes place in the nucleus of the cell. This produces mRNA which is small enough to leave the nucleus through its pores in the envelope. 2. Once the mRNA exits, it moves towards ribosomes that may be free floating in the cytoplasm or attached to the RER 3. Once mRNA attaches to the ribosome, tRNA comes along. tRNA is composed of amino acids and anticodons (every 3 bases of tRNA) . 4. In this process, every 3 bases of mRNA (a codon) is read and tRNA attaches a specific and complimentary anticodon that pairs with it and forms temporary hydrogen bonds 5. For every pair of codon and anticodon, the tRNA carries the specific amino acid that the mRNA codes for. 6. This continues along the mRNA in which the enzyme peptidyl transferase forms peptide bonds between the amino acids to form a protein. 7. The process of translation continues until stop protein is reaches, which signals the end of the protein synthesis. 8. The sequence of amino acids in the newly formed polypeptide determines the final structure of the protein.

Question 33

What does a tRNA composed of

Answer 33

An anticodon and an amino acid

Question 34

Whats an anticodon

Answer 34

Every 3 bases of tRNA, they are complimentary to codons of mRNA

Question 35

What does it mean that dna is degenerate

Answer 35

• Genetic code is degenerate this means that some amino acids can be coded for by multiple different codons. There are 64 codons combination but only 20 amino acids

Question 36

What does it mean that dna is overlapping

Answer 36

• Genetic code is non – overlapping , meaning each 3 bases is only read. Once the adjacent codons do not overlap, and no single base can take part in the formation of more than one codon

Question 37

What does it mean that dna is universal

Answer 37

• Genetic code is universal meaning each codon codes for the same amino acid in all living things