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Biology > DNA and the Genetic code > Flashcards

DNA and the Genetic code Flashcards

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1
Q

Components of a nucleotide

A
  • Phosphate group
  • Deoxyribose sugar
  • Organic base
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2
Q

Where DNA and RNA is found inside cells

A
  • In eukaryotic cells, DNA is found in the nucleus

- RNA is usually found in the cytoplasm

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3
Q

Sugars present in RNA and DNA

A

DNA- Deoxyribose

RNA – Ribose

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4
Q

How are nucleotide chains made?

A
  • They are made by condensation reactions between the carbon 5 and the carbon 3 with the phosphate groups
  • Also complementary base pairs will form hydrogen bonds with each other
  • Water molecules are formed when nucleotide chains are formed
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5
Q

How are nucleic acids made?

A

When nucleotide chains bond together

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6
Q

The five organic bases

A

Purines – Adenine, Guanine

Pyrimidines – Thymine, Cytosine, Uracil

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7
Q

Problems with too much nucleic acid

A
  • Uric acid is produced when excess purines are hydrolysed in the liver
  • Uric acid is normally excreted through the urine system
  • As uric acid is normally insoluble at lower temperatures, when in excess can form crystal deposits at areas of the body where bloodflow is weak
  • This condition is painful and is reffered to as gout
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8
Q

Nitrogenous

A

Contains nitrogen

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9
Q

Nucleotide

A

The monomeric unit of all nucleic acids

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10
Q

DNA

A

The stable polynucleotide chain that acts as an information store as each organic base helps code for amino acids

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11
Q

Importance of DNA being a stable molecule

A

The hydrogen bonding between the bases makes the molecule stable. Without this stability, the genetic sequence could end up being changed easily and things could go very wrong

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12
Q

DNA structure

A
  • Made from two polynucleotide chains that are anitparallel to each other
  • Double helix shape
  • Made up of a sugar phosphate backbone
  • Sugar phosphate back bone is held together by phosphodiester bonds
  • Complementary bases are held together by H-bonds
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13
Q

Process of making a new copy of DNA

A

-Double helix structure is untwisted
-H-bonds are broken by DNA helicase
-Complemetary bases are unzipped
-Nitrogenous bases are exposed
-DNA polymerase
uses free nucelotides to re bond exposed bases according to base pairing rules

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14
Q

Semi conservative replication

A

The replication of DNA where a DNA strand unzips and a new strand is assembled onto each conserved strand according to base pairing rules

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15
Q

Advantages of the DNA structure

A
  • The sequence of bases are a good code for information
  • Molecules are long so a lot of information can be stored
  • Base pairing rule means that complementary strands of DNA can be replicated
  • Double helix structure gives the molecule stability
  • H-bonds break easily so allow for easy unzipping and copying of information
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16
Q

Gene

A

The sequence of amino acids that code for a specific protein

17
Q

Difference between RNA and DNA

A
  • In RNA, sugar molecule that makes up nucleotides is ribose
  • The nitrogenous base thymine is replaced with urcail
  • The poly nucleotide chain is usually single stranded
  • Three forms of RNA exist
18
Q

The three forms of RNA

A
  • mRNA
  • tRNA
  • rRNA
19
Q

Function of mRNA

A

mRNA or messenger RNA exists to send the information of how to assemble the amino acids found to form protein in the ribosomes. This happens during protein synthesis inside the cell.

20
Q

What does degenerate mean?

A

Some amino acids in the genetic code have more than one codon

21
Q

What is the advantage for the genetic code to be degenerate?

A

If a mutation occurs on the third base, it may not affect the coded amino acid

22
Q

What does non-overlapping mean?

A

There is no sharing of bases between codons

23
Q

What is a triplet sequence?

A

When amino acids are read in groups of three codons

24
Q

What is the purpose of a stop codon?

A

To tell the ribosome where the protein should end

25
Q

How does the messelsohn and Stahl’s experiment work?

A

An organism is grown in a medium of heavy N15 so all DNA is tagged with N15
Oragnisms are transferred to a medium containing N14 where they replicate once
This produces organisms with N14N15 DNA
As the organisms replicate further, the N14N15 DNA will halve at every replicate
This provides evidence for semi-conservative DNA replication

26
Q

How can you prove the Messelsohn and Stahl’s experiment?

A

By putting the sample at each stage of replication in a density centrifuger and observeing the positions where the rings of DNA appear and in what abundance

27
Q

What is the function of tRNA in DNA replication?

A

tRNA brings the relevent amino acids that are complementary to the mRNA amino acid sequence

28
Q

What is the structure of tRNA like?

A

80 nucleotides long
Polypeptide chains fold up and are stabilised by H-bonds
Structure is simplified as a hairpin structure
Always terminates with CCA

29
Q

What is the problem with too much nucleic acid in the blood?

A

Uric acid is produced when excess purines are hydrolysed in the liver
Uric acid is normally excreted into urine
As uric acid is insoluble at warmer temperatures and when in axcess can form crystal deposits at the toes
This condition is painful and is known as gout

30
Q

Why can DNA not leave the nucleus through nuclear pores?

A

DNA is physically attached to the inside of the nuclear envelope
It is physically too large to leave the nuclear pores

31
Q

Why is mRNA shorter than a DNA molecule?

A

mRNA only codes for one protein sequence while DNA codes for many proteins

32
Q

What is transcription?

A

The assembly of an mRNA molecule that is a copy of the DNA coding strand

33
Q

What are histone proteins?

A

Proteins that allow DNA to wrap around itself to forma chromatin structure

Biology (18 decks)

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