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Mutation
a change within the original DNA sequence
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A mutation may change __
- one or more amino acids coded by a gene. Varieties of mutations may happen in a gene causing different effects. Depending on the mutation, it may cause a mild, moderate, or severe change in the function of the coded protein. ex. Mutation in the beta globin gene causes sickle cell anemia.
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chromosome
- a genetic structure made of long DNA molecules and the proteins associated with the DNA
- (Human cells have 46 chromosomes: 22 pairs of somatic chromosomes & XX or XY)
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genes
- parts of the DNA molecule of each chromosome. The order of the nucleotides in a gene codes for a particular protein or a particular function
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genome
- the entire genetic complement of a living organism that contains the biological info needed to construct & maintain a living example of that organism
- - made of DNA in most organisms
- - made of RNA in some viruses
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The general structure of DNA is __ in different organisms & in different genes.
the same
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The main difference in the structure of DNA is __
- the order of nucleotides in the DNA
- Some specific sequences of nucleotides may affect the general structure of DNA to some extent.
- Some viruses may have a single strand of DNA as their genome.
- There are also circular DNA instead of linear DNA
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The carbons of deoxyribose are numbered with __
prime (1' to 5')
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Each base is attached to the __ of the sugar by a __ bond
- carbon 1'; glycosidic
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Deoxyribose & phosphate are linked by __ bonds
- ester
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pyrimidines
- cytosine & thymine
- both made of a single heterocyclic ring
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purines
- adenine & guanine
- both made of a double heterocyclic ring
- (Caffeine is also a purine but not part of the DNA structure.)
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Pyrimidines bind to deoxyribose by their __. Purines bind to deoxyribose by their __.
N1; N9
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In nucleotides, bases can occur as either form of 2 alternative __ (structural isomers that are in dynamic equilibrium)
- tautomers
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base + sugar = __
- base + sugar + phosphate (1 or 2 or 3) = __
- nucleoside; nucleotide
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DNA is a polymer of __
nucleotides
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The backbone of DNA (the poles of the ladder) is made of __ & the steps of the ladder are made of __
- the alternates of deoxyribose & phosphate; bases
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Because of the __, DNA has a negative charge
phosphates
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In one strand of DNA, nucleotides can be arranged in __
any order (any nucleotide can follow the same or anyother nucleotide)
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The 2 strands run in __ direction.
antiparallel (opposite)
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__ bonds are made between G & C
- 3 hydrogen
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__ bonds are made between A & T
- 2 hydrogen
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In normal conditions & the dominant tautomers, base pairing between G & C and A & T is very specific because there is a __ between the mismatch bases.
- steric hindrance
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The structure of DNA is stabilized by __
- base pairing (hydrogen bonds)
- by bases being stacked on top of each other
- - almost perpendicular with the axis of the helix
- - flat & not very H2O soluble
- - hydrophobic & Van der Waal interactions between stack of bases
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Bases can be flipped out of the double helix one by one. This phenomena seems to be implemented by some enzymes that are involved in:
- methylation of bases
- removing the damaged bases
- DNA repair
- homologous recombination
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DNA is a __ handed double helix
- right (counter-clockwise)
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Almost __ bases makes a full turn of the helix
10
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On one side of each glycosidic bond, the less open angle is __ & on the other side of it, it is __.
- ~120 degrees (the minor groove);
- ~240 degrees (the major groove)
- Major grooves are more important for interaction of proteins with DNA as they are wider (more room for interactions)
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It is possible to differentiate base pairs from each other by considering the chemical codes of __
- major grooves
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The chemical codes of __ are not very different between G:C & C:G and between A:T & T:A, but G:C & C:G can be differentiated from A:T & T:A and vice versa.
- minor grooves
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