Genetics: Mutations L2

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  • Created by: Alex
  • Created on: 09-04-13 17:34
What's a base (Nitrogenous)
Nucleotide or Nucleic acid - Molecular component of DNA - main types are Adenine, Guanine, Cytosine, Thymine and Uracil(RNA only)
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Nucleotide
A molecule consisting of one or more phosphate groups, a 5-carbon sugar(Ribose or Deoxyribose) and a nitrogenous base(Purine or Pyrimidine)
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Nucleoside
A Base and a sugar (Ribose or deoxyribose)
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Purine
Nitrogenous base with carbon and nitrogen atoms attatched in two rings - Adenine and Guanine
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Pyrimidines
Nitrogenous bases, composed of a single ring of carbon nd nitrogen atoms - Thymine, Cytosine and uracil
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Codon
Triplet of mRNA nucleotdies - encode for an amino acid or a signal to start/stop protein synthesis
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Mutation
Any change in genetic information/DNA different to the wild type genome - include change in base pairs, order of genes in chromosomes (so interactions produce different effects) or change in chromosomes themselves
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Chromatin
The complex of DNA and protein that makes up eukaryotic chromosomes
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Mutagen
Any agent capable of entering the cell and producing mutations
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DNA Polymerase
an enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. used in DNA replication, in which the polymerase "reads" an intact DNA strand as a template and uses it to synthesize the new strand
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Number of amino acids
20
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Bonds that join DNA strand in a helix
hydrogen bonds
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Number of bonds between Adenine and Thymine
2
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Number of bonds between Guanine and cytosine
3
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Nucleotides in RNA
A-U (instead of T) G-C
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Starting codon
AUG - Methionine
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Stop Codons
3 - UAA, UAG, UGA
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Types of Mutations
Point, Instertations, Deletions, Duplications, Chromosomal changes
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Source of Mutation
DNA polymerase errors during replication, External effects e.g chemicals and radiation and failure of repair mechanisms
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DNA Polymerase
is an enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. Used in DNA replication, in which the polymerase "reads" an intact DNA strand as a template and uses it to synthesize a new strand
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Mechanisms of mutations
Physical: X-rays and UV light Chemical : Base analogues, Base modifying agents and intercalating agents
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Base analouges
A chemical that resembles a naturally occurring *purine or *pyrimidine base to the extent that it may be incorporated into a DNA molecule during replication. Analogues are less specific in their pairing properties e.g. 5-bromouracil
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5-bromouracil
Analogue of thymine , bromine replaces the methyl group on C5 ring. During replication the analogue may be included instead of thymine. Multiple replications a T:A pair could be replaced by a C:G pair point mutation
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Base modifying agent
directly modifies the structure or chemical properties of bases. An example of this is nitrous oxide which is a deaminating agent (converts C to U).
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Intercalating agent
are molecules that may insert between bases in DNA, causing deletions & frameshift mutation during replication. e.g proflavin
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Somatic Mutation
Occurs in somatic(body) cells - only affects the individual in which the mutation occurs - dnot inherited
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Germline mutation
Occurs in egg/sperm (Germ-line) may be transmitted by gametes to the next generation - produces an individual with the mutation in somatic and germ-line cells
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Gamete
A sex cell - egg/sperm. The union of gametes results in the formation of a zygote. 1n
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Zygote
2n cell that results from union of n gametes in sexual reproduction
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Point Mutation
Involve only one base pair, can be insertions, deletions or substitutions
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BP Substitution
Replaces one base with another - can be a transition or transversion change
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Transition BP substitution
Replaces the base with one of the same chemical category - Purine to Purine etc
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Transversion BP substitution
Replacement of a base of one chemical category to one of the other - Purine to Pyrimidine etc
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Effects of Base Pair substitutions
Nonsense mutations, missense mutations, neutral mutations and silent mutations
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Nonsense mutation
change of codon to a stop/start mutation
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missense mutation
base pair change resulting in a different mRNA codon - anticodon codes for a different amino acid
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Neutral mutation
change in codon and amino acid but no detectable change in the protein
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Silent nutation
Base pair changes but still encodes for the amino acid in the wild type gene, thus no effect on the protein
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Base-Pair Deletion/Insertion problems
Causes Reading Frame to be Shifted
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Frame shift problems
may bring/remove stop codons into frame- shortening or lengthening protein. causes incorrect coding of amino acids - protein is incorrect. Doesn't occur(as seriously) if number inserted/deleted is divisible by 3
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Induced mutatagens
Physical - Radiation (X-rays and UV) and Chemical -Base analogues, Base modifying agents and Intercalating agents
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X-rays
Penetrate tissues, Knock electrons out of orbits and create ions, ions break covalent bonds (Sugar-phosphate backbone), broken bonds cause interchanges between chromosomes, low doses cause point mutations, high doses kill cells
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UV light
photochemical changes in DNA - low energy wave'lengths absorbed by purines and pyrimidines forming abnormal chemical bonds
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Other cards in this set

Card 2

Front

Nucleotide

Back

A molecule consisting of one or more phosphate groups, a 5-carbon sugar(Ribose or Deoxyribose) and a nitrogenous base(Purine or Pyrimidine)

Card 3

Front

Nucleoside

Back

Preview of the front of card 3

Card 4

Front

Purine

Back

Preview of the front of card 4

Card 5

Front

Pyrimidines

Back

Preview of the front of card 5
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