2.3 Nucleotides

Question 1

What is semiconservative replication

Answer 1

Two new molecules of DNA are formed, each with one old strand of DNA

Question 2

What is nucleotides made from

Answer 2

Phosphate group, Pentose sugar, nitrogenous base,

Question 3

What is one strand of DNA made from

Answer 3

Many nucleotides bonded together via phosphodiester bonds

Question 4

What reaction creates DNA

Answer 4

Condensation

Question 5

What reaction breaks down DNA

Answer 5

Hydrolysis

Question 6

What is A double Helix of DNA made from

Answer 6

two strands of DNA running anti parallel to one another,

Question 7

A T C G

Answer 7

Adenine, Thymine, Cytosine, Guanine

Question 8

What are pyrimidines

Answer 8

Smaller bases - one ring - Thymine and cytosine

Question 9

What are purines

Answer 9

Larger bases - two rings - Adenine, Guanine

Question 10

What bases complimentory bond together

Answer 10

Adenine (2 hydrogen bonds)- Thymine
Cytosine (3 hydrogen bonds)- Guanine

Question 11

Explain DNA replication

Answer 11

DNA helicase unzips two strands of DNA, free nucleotides in the nucleoplasm attach to their complementary base, DNA polymerase creates phosphodiester bonds between bases, Products are identical and contain one original strand

Question 12

How are Okazaki fragments formed

Answer 12

DNA polymerase can only bind to the 3’ side, so moves from 3’ 5’ direction. The 5’ to 3’ (lagging strand) strand DNA polymerase has to wait until another section has been unwound. (discontinuous replication)

Question 13

What happens to Okazaki Fragments

Answer 13

Ligase join Okazaki fragments on the lagging strands

Question 14

What is DNA mutation?

Answer 14

Errors (change in the sequence of bases) created randomly

Question 15

What is the Genetic code? What are 3 features about it?

Answer 15

DNA coding for an amino acid.
Triplet code - read in threes (codon)
Degenerate - Codons are not overlapping. amino acids can be coded for by many codons
Universal - genetic code is the same for most organisms

Question 16

What is a start codon?

Answer 16

Met - Codon that starts of DNA translation/transcription, signalling the start of a gene

Question 17

Put the order of Protein synthesis

Answer 17

Replication, Transcription, Translation

Question 18

What is the difference between coding and template strands

Answer 18

The strand we want to copy is called the coding strand, The template strand is the one we transcribe

Question 19

What are the 4 bases of RNA

Answer 19

Adenosine, Uracil, cytosine, Guanine

Question 20

Pair complementory bases in RNA

Answer 20

Adenine - Uracil
Cytosine - Guanine

Question 21

Explain DNA transcription

Answer 21

RNA helicase unzips DNA. Free RNA nucleotides pair with complementary bases on the template strand. Phosphodiester bonds form on the RNA nucleotides by the enzyme RNA polymerase. mRNA is formed, which is an exact copy of the Coding strand and complementary to the template strand, but with Uracil, instead of Thymine. MRNA detaches from the DNA, and leaves the nucleus through nuclear pores. Double Helix reforms

Question 22

What is ribosomes split into, what does it contain

Answer 22

Small and large subunit, contains ribosomal RNA

Question 23

What is the anticodon on tRNA. What does tRNA do?

Answer 23

Anticodon is complementary to mRNA strand. tRNA brings over amino acid, corresponding to that codon

Question 24

Explain DNA translation

Answer 24

mRNA bonds to small subunit of ribosome, at the start codon. tRNA with complimentary anticodon then binds to the mRNA, only two tRNA can be bound at the same time. Peptide bonds are created between amino acids, catalysed by an enzyme. Ribosome moved down mRNA chain, until it reaches a stop codon, where the primary structure is released. The protein then folds into secondary and tertiary structures

Question 25

What happens to proteins after translation

Answer 25

Protein moves to Golgi apparatus, to be modified

Question 26

Explain the Mendel and Starr experiment

Answer 26

Two colonies of bacteria grown, one in 14N (normal) and 15N (Heavy) After many generations of growing in N15, they were transferred into N14. Samples were taken from the first generation, second generation... and analysed to the control

Question 27

What does the Mendel and Starr experiment prove. How?

Answer 27

Semi-conservative replication. in the first generation, there is one band in the middle of N15 and N14, showing that it is a mix of DNA. in the second generation, there are two bands, one at N14, and one at a mix of N15 and N14, as one is from pure N14 and another is mixed with N15