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Biology A Level > DNA > Flashcards

DNA Flashcards

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1
Q

What biological molecules make up a nucleotide?

A

Sugar (deoxyribose).
Phosphate group.
Nitrogenous base - two types - purines/pyrimidines.

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2
Q

What are the four bases in DNA’s alphabet?

A

Adenine (A) - a purine.
Cytosine (C) - a pyrimidine.
Guanine (G) - a purine.
Thymine (T) - a pyrimidine.

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3
Q

What are the only two pairs within the DNA’s alphabet?

A

The only two pairs within the DNA’s alphabet are A always pairs up with T and C always pairs with G.

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4
Q

What is the bond between the backbone and the phosphate sugar called?

A

A phosphodiester bond.

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5
Q

How many hydrogen bonds are between the par of bases adanine and thymine?

A

2 hydrogen bonds.

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6
Q

How many hydrogen bonds are between the pair of bases cytosine and guanine?

A

3 hydrogen bonds.

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7
Q

On which bond does the phosphate sugar join onto in a nucleotide?

A

-Phosphate sugar joins onto the nitrogenous base on the second bond.

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8
Q

What is the only cell in the human body that doesn’t contain DNA and why?

A

Only cell in the body that doesn’t have any DNA is red blood cells as red blood cells don’t have a nucleus so they have no DNA information.

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9
Q

What percentage of DNA is made up of the pair of bases Adanine and Thymine?

A

68% of DNA is made up of the bases Adanine and Thymine.

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10
Q

What percentage of DNA is made up of the pair of bases Cytosine and Guanine?

A

32% of DNA is made up of the DNA bases Cytosine and Guanine.

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11
Q

What does a nucleotide consist of?

A

One phosphate sugar + one deoxyribose group + a nitrogenous base.

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12
Q

What are the elements in DNA?

A

Nitrogen, Oxygen, Carbon and Hydrogen.

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13
Q

What is the function of the Phosphate Sugar backbone in DNA?

A

Ads rigidity to the DNA so it doesn’t lose its shape and protects the inside (the crucial information) from any damage from the outside.

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14
Q

What is the function of the bases in DNA?

A

They bind together to ensure that the DNA strands are bonded together and in a certain way due to the fact each base has an individual shape which is unchangeable and because each base can only pair to another one as there are only 2 nitrogenous base pairs, then the DNA strand will always maintain the same width so it does not lose shape and protects the inside (the crucial information) from any damage from the outside.

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15
Q

What is the function of the double helix in DNA?

A

Makes it more efficient due to the fact it makes it smaller with a smaller surface area = can fit into a variety of parts and more can be crammed into the nucleus so there are more copies of genetic information so that if there are faults there are others. Also it helps add to the structures rigidity and strength as it is less breakable then as it is stronger and therefore harder to break, protecting the inside (the crucial stuff) from any harm from the outside.

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16
Q

What does RNA stand for?

A

Ribonucleic acid.

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17
Q

How is RNA different to DNA?

A

RNA has only one backbone/RNA is single stranded. DNA is a double-stranded molecule. DNA = double because of D at the front whereas R is only single.
It also doesn’t have a deoxyribose group, it has a ribose group instead of this group.
RNA doesn’t have thymine in it, it has Uracil instead.
RMA has one more oxygen than DNA, DNA has one less than RNA

18
Q

What replaces Thymine in RNA?

A

Uracil

19
Q

What does Uracil replace from DNA in RNA?

A

Thymine.

20
Q

What are the similarities between RNA and DNA?

A

Both contain oxygen.
Both made up of monomers called nucleotides.
DNA + RNA both have 3 nitrogenous bases: Adenine, Cytosine and Guanine.
DNA and RNA both have phosphate groups in their nucleotides, sometimes called phosphoric acid.
Both necessary to produce proteins.
DNA makes RNA which is then translated into protein.

21
Q

What are the differences between RNA and DNA?

A

RNA has one more oxygen than DNA, DNA has one less than RNA.
DNA is double-stranded, RNA is single-stranded.
DNA contains a pentode sugar Deoxyribose, RNA contains the pentane sugar Ribose. A pentode is a 5-carbon sugar molecule.
DNA is limited to the nucleus, RNA is made in the nucleus, but can travel outside of it, through the cytoplasm to the ribosomes to produce proteins and to create copies of DNA.
DNA has a nitrogenous base called Thymine, but RNA doesn’t. Instead, RNA has Uracil. In DNA, Thymine pairs with adenine, but in RNA Uracil pairs with adenine.
There is only one type of DNA but 3 kinds of RNA (messenger, transfer and ribosomal RNA).

22
Q

What are the steps to DNA replication?

A

Enzyme DNA helicase breaks the hydrogen bonds linking bases of DNA and unwinds double helix structure separating them into their two strands + unwinds. DNA helicase ‘unzips’ the double helix structure of a DNA molecule.
Easy exposed polynucleotide strand = acts as template to which free nucleotides bund by specific base pairing. A –> T, C –> G.
DNA polymerase helps copy the strands of DNA.
New bases will pair up with their complimentary pairs (will only be one to fit it due to the fact that bases have a specific shape).
They will create covalent bonds between the phosphate group.

23
Q

How do the functions of molecules in DNa help improve the function of DNA?

A

Stable molecule:

  • phosphodiester backbone protects the more chemically reactive organic bases inside the double helix
  • Hydrogen bonds link the original base pairs forming bridges (rungs) between the phosphodiester uprights/backbones. As there are three hydrogen bonds between cytosine and guanine, the higher the proportion of C-G the more stable the DNA molecule.
  • Other interactive forces between the base pairs that hold the molecule together (=base stacking).
24
Q

What is the function of DNA?.

A
  • hereditary material responsible for passing on information from cell to cell + generation to generation.
  • About 3.2 billion base pairs in DNA of a typical mammalian cell. Vast number = almost infinite variety of sequences of bases along length of DNA molecule.
  • It’s variety provides genetic diversity within living organisms.
25
Q

What are the 3 major differences between DNA and RNA?

A
  • RNA is single-stranded molecule, no double helix.
  • Sugar in RNA is ribose (one more oxygen than the sugar in DNA (deoxyribose sugar)).
  • RNA does NOT contain thymine, it’s fourth base is uracil, so that bonds with adenine instead.
26
Q

What is a codon?

A

Any three DNA bases that code for an amino acid.

27
Q

What does the term degenerate mean?

A

More than one triplet code codes for the same amino acid.

28
Q

What is a triplet code?

A

It is a code which is read in threes.

29
Q

What does the term non-overlapping mean?

A

Any base can be involved in one amino acid. Each base is only used once, you can’t reuse a codon/base again when reading along the chain.

30
Q

What does the term universal mean?

A

The same 3 bases code for the same amino acid in every living organism.

31
Q

What is a gene?

A

It is a section of DNA at a particular/specific loci/locus which codes for a single polypeptide. This gene is located on a particular place on a chromosome.

32
Q

What is the universal start code for RNA?

A

AUG.

33
Q

What does DNA stand for?

A

Deoxyribonucleic acid.

34
Q

How are two nucleotides joined?

A

The deoxyribose sugar of one mononucleotide and the phosphate group of another join together by a condensation reaction.

35
Q

What type of bond is formed when two mononucleotides join together?

A

The bond between two mononucleotides is a phosphodiester bond to form a dinucleotide.

36
Q

Why does a higher percentage of cytosine and guanine bonds to adenine and thymine bonds mean a stronger molecule?

A

Because there are three hydrogen bonds between cytosine and guanine, so therefore the higher the proportion of cytosine to guanine pairings, the more stable the DNA molecule is.

37
Q

Why are the base pairings always cytosine to guanine and adenine to thymine?

A

To ensure a standard ‘rung’ length. Also the ‘uprights’ also run in the opposite direction to each other (i.e. are antiparallel).

38
Q

How is DNA as a molecule stable?

A

Phosphodiester bond protects more chemically reactive organic bases inside the double helix structure of DNA.
Hydrogen bonds link organic bases forming bridges (rings) between phosphodiester uprights. Three hydrogen bonds between cytosine and guanine, so therefore, higher proportion of cytosine to guanine pairings = the more stable the DNA molecule is.
Other interactive forces between base pairs holds the molecule together = base stacking.

39
Q

What is the function of DNA?

A

DNA = the hereditary material that transfers genetic information from cell to cell and generation to generation. In a typical mammalian cell = around 3.2 billion base pairs in the DNA. This vast number = almost an infinite variety of sequences of bases along te length of a DNA molecule. This variety provides genetic diversity within lining organisms.

40
Q

How is DNA adapted to carry out its function of carrying hereditary material from cell to cell and generation to generation? (5/6 reasons why).

A

Very stable structure - normally passes from generation to generation without change - only rarely does it mutate.
Two separate polynucleotide chains = joined together by hydrogen bonds allowing them to separate easily (hydrogen bonds = weak so can break easily during DNA replication + protein synthesis.
Extremely large molecule - carries an immense amount of genetic information.
Base pairs = within helical cylinder of deoxyribose-phosphate backbone, so genetic information = to some extent protected from being corrupted by outside chemical and physical forces.
Base pairing leads to DNA being able to replicate and transfer information as mRNA.
Function of molecule of DNA depends on sequence of base pairs that it possesses. Sequence = important to everything it does and life itself.

41
Q

What is the 5’ 3’ organisation of DNA?

A

5’ (5 prime1) carbon has an attached phosphate group and 3’ (3 prime) has a hydroxyl group.
When nucleotides are arranged into double strands of DNA molecule, one strand runs 5’ to 3’ direction + other runs 3’ to 5’ direction, so two strands = antiparallel.
Nucleic acids can only be synthesised ‘in vivo’ in 5’ to 3’ direction as enzyme DNA polymerase that assembles nucleotides into a DNA nucleotide can only attach nucleotides to the hydroxyl (OH) group (due to it’s specific active site shape) on the 3G’ carbon molecule.

42
Q

What is a silent mutation?

A

A mutation that is not picked up/alter the amino acid sequence.

Biology A Level (13 decks)

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