Nucleotides and nucleic acids

Question 1

What are Nucleotides and what are they made up of?

Answer 1

A Nucleotide is a type of biological molecule. It is made up of a pentose sugar, a nitrogenous base, and a phosphate group. They all contain the elements C, H, O, N, and P.

Question 2

What are Nucleotides used for?

Answer 2

They are used as the monomers that make up DNA and RNA (both types of nucleic acid).

Question 3

What are the different uses of DNA and RNA?

Answer 3

DNA is used to store genetic information- the instructions an organism needs to grow and develop.
RNA is used to make proteins from the instructions in DNA.

Question 4

What are ADP and ATP?

Answer 4

They are special types of nucleotides. They’re used to store and transport energy in cells.

Question 5

What is the name of the pentose sugar in DNA?

Answer 5

Deoxyribose

Question 6

What is the difference between each DNA nucleotide?

Answer 6

They all contain the same phosphate and sugar group except the base on the nucleotides can vary

Question 7

What are the four possible base pairs?

Answer 7

Adenine, Thymine, Guanine, Cytosine

Question 8

What are purine bases?

Answer 8

A purine base contains two carbon-nitrogen rings joined together. The two purine bases are Adenine and Guanine

Question 9

What are pyrimidine bases?

Answer 9

A pyrimidine base contains only one carbon-nitrogen ring. It is smaller than a purine base. The two Pyrimidine bases are Cytosine and Thymine.

Question 10

What is the structure of a molecule of DNA?

Answer 10

A molecule of DNA contains two polynucleotide chains- each chain is made up of lots of nucleotides joined together. They form a double helix structure.

Question 11

What is the name of the pentose sugar in RNA?

Answer 11

Ribose

Question 12

What is the difference in bases in RNA and DNA?

Answer 12

Instead of Thymine Uracil replaces it.

Question 13

What is the structure of a molecule of RNA?

Answer 13

An RNA molecule is made up of a single polynucleotide chain.

Question 14

How do you phosphorylate a nucleotide?

Answer 14

You add one or more phosphate groups to it.

Question 15

What is ADP?

Answer 15

Adenosine diphosphate: contains the base adenine, the sugar ribose, and two phosphate groups.

Question 16

What is ATP?

Answer 16

Adenosine triphosphate: contains the base adenine, the sugar ribose, and three phosphate groups.

Question 17

What is the process of releasing energy using ATP and ADP?

Answer 17

1) ATP provides energy for chemical reactions in the cell.
2) ATP is synthesized from ADP and inorganic phosphate, using the energy from an energy-releasing reaction (like the breakdown of glucose in respiration). The ADP is phosphorylated to form ATP and a phosphate bond is formed.
3) Energy is stored in the phosphate bond. When this energy is needed by a cell, ATP is broken back down into ADP and inorganic phosphate. Energy is released from the phosphate bond and used by the cell.

Question 18

How do nucleotides join together to form polynucleotides?

Answer 18

The nucleotides join up between the phosphate group of one nucleotide and the sugar of another via a condensation reaction.
This bond is called a phosphodiester bond. (phosphate group and two ester bonds)
They can be broken down into nucleotides again by breaking the phosphodiester bonds via hydrolysis

Question 19

What is the chain of sugars and phosphates known as in DNA?

Answer 19

The sugar-phosphate backbone

Question 20

How do two DNA polynucleotide strands join together?

Answer 20

hydrogen bonding between the bases

Question 21

What is complementary base pairing?

Answer 21

This is when each nitrogenous base can only join with one particular partner

Question 22

What does Adenine pair with?

Answer 22

Thymine in DNA and Uracil in mRNA

Question 23

What does Cytosine pair with?

Answer 23

Guanine

Question 24

What are purines and pyrimidines?

Answer 24

Purines are two-ring structures while pyrimidines are single-ring structures

Question 25

How many hydrogen bonds form between A-T and G-C

Answer 25

two between A-T and three between G-C

Question 26

How is the DNA double helix formed?

Answer 26

Two antiparallel polynucleotide strands twist to form the DNA double helix

Question 27

How can you purify DNA?

Answer 27

1) break up the cells in your sample using a blender
2) make up a detergent, salt, and distilled water solution
3) add cells to the beaker with the detergent solution and put in a 60-degree water bath for 15 minutes
4) put the beaker in an ice bath to cool it down and then filter the mixture
5) Add protease enzymes
6) Add cold ethanol so it forms a layer above
7) Leave for a few minutes and DNA should form a white precipitate

Question 28

What does the detergent do in the purification of DNA?

Answer 28

The detergent in the mixture breaks down the cell membranes. The salt binds to the DNA and causes it to clump together. The temperature of the water bath should stop enzymes in the cells from working properly and breaking down the DNA.

Question 29

How does DNA undergo self-replication?

Answer 29

1) DNA helicase breaks the hydrogen bonds between the two polynucleotide strands (where base pairs interact) (unzips)
2) Each strand acts as a template for a new strand. Free-floating DNA Nucleotides join to the exposed bases on each stand via complementary base pairing
3) Nucleotides of the new strand are joined together by DNA polymerase to form the sugar-phosphate backbone. Hydrogen bases form between the original and new strand which then twists to form a new double helix
4) both new DNA molecules contain one new and one original strand

Question 30

What is semi-conservative replication?

Answer 30

It is a type of DNA self-replication where half the strands in each new DNA molecule are from the original piece of DNA

Question 31

Why is DNA replication so accurate?

Answer 31

It needs to be done to make sure genetic information is conserved each time the DNA is replicated in the cell

Question 32

When are abnormal proteins produced (DNA)?

Answer 32

Sometimes a random spontaneous mutation occurs ( a change to the DNA base sequence). Mutations don’t always have an effect, but they can alter the sequence of amino acids in a protein. This can cause an abnormal protein to be produced. The abnormal protein might function better or not at all.

Question 33

What are genes in DNA?

Answer 33

A gene is a sequence of DNA nucleotides that codes for a polypeptide/protein
Different proteins have different numbers and orders of amino acids
It is the order of nucleotide bases in a gene that determines the order of amino acids in a particular protein
Each amino acid is coded for by a sequence of three bases called a triplet in a gene

Question 34

How is DNA copied into RNA for protein synthesis?

Answer 34

DNA molecules are found in the nucleus while ribosomes are found in the cytoplasm
DNA is too large to exit the nucleus so a section is copied into mRNA and this process is called transcription
The mRNA exits the nucleus and joins with a ribosome in the cytoplasm where it can be used to synthesise a protein. This process is called translation

Question 35

What is Messenger RNA?

Answer 35

It is made in the nucleus and three adjacent bases are called a codon/triplet
It carries the genetic code from the DNA in the nucleus to the cytoplasm, where it’s used to make a protein during translation.

Question 36

What is Ribsomal RNA?

Answer 36

It forms the two subunits in a ribosome (along with proteins)
The ribosome moves along the mRNA strand during protein synthesis. The rRNA in the ribosome helps to catalyze the formation of peptide bonds between the amino acids.

Question 37

What is Transfer RNA?

Answer 37

Found in the cytoplasm. It has an amino acid binding site at one end and a sequence of three bases at the other end called an anticodon.
It carries the amino acids that are used to make proteins to the ribosomes during translation

Question 38

What is genetic code?

Answer 38

The genetic code is the sequence of base triplets (codons) in DNA and mRNA, which codes for specific amino acids.

Question 39

What does non-overlapping genetic code mean?

Answer 39

Each base triplet is read in sequence, separate from the triplet before and after it. Base triplets don’t share their bases

Question 40

What does degenerate genetic code mean?

Answer 40

There are more possible combinations of triplets than there are amino acids (20 AA and 64 possible triplets). This means that some amino acids are coded for by more than one base triplet e.g. tyrosine is UAU or UAC

Question 41

What are start and stop codons?

Answer 41

They are the triplets that are used to tell the cell when to start and stop the production of the protein. They are found at the beginning and end of the gene.

Question 42

What does universal genetic code mean?

Answer 42

It means the same specific base triplets code for the same amino acids in all living things.

Question 43

What are the steps in Transcription?

Answer 43

1) Transcription starts when RNA polymerase attaches to the DNA double-helix at the beginning of a gene.
2) The hydrogen bonds between the two DNA strands in the gene break, separating the strands, and the DNA molecule uncoils at that point.
3) One of the strands is then used as a template to make an mRNA copy.
4) The RNA polymerase lines up free RNA nucleotides alongside the template strand. Complementary base pairing means that the mRNA strand ends up being a copy of the DNA template strand (except T is replaced by U).
5) Once the RNA nucleotides have paired up with their specific bases on the DNA strand they’re joined together, forming an mRNA molecule.
6) The RNA polymerase moves along the DNA, separating the strands and assembling the mRNA strand.
7) The hydrogen bonds between the uncoiled strands of DNA re-form once the RNA polymerase has passed by and the strands coil back into a double-helix.
8) When RNA polymerase reaches a stop codon it stops making mRNA and detaches from the DNA.
9) The mRNA moves out of the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm, where the next stage of protein synthesis takes place.

Question 44

What are the steps in Translation?

Answer 44

1) The mRNA attaches itself to a ribosome and tRNA molecules carry amino acids to the ribosome
2) The tRNA has a complementary anticodon to the codon on the mRNA meaning it attaches
3) A second tRNA molecule attaches itself to the next codon in the same way
4) rRNA in the ribosome catalyzes the formation of a peptide bond between the two amino acids. Then the first tRNA molecule detaches and leaves
5) A third tRNA molecule and protein join and everything is shifted and repeated again producing a chain of amino acids (polypeptide chain) it stops when there is a stop codon.
6) Finally the polypeptide chain moves away from the ribosome

Question 45

What are ozaki fragments?

Answer 45

Okazaki fragments are short sequences of DNA nucleotides that are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication.