DNA and the genetic code W3 Flashcards
DNA is a polymer of
nucleotides
each nucleotide that composes DNA has three components:
phosphate sugar base
what are the four bases
A C T G
what the name of the sugar in DNA
doxyribose
what are the two purine bases
A - adenine G - guanine
what are the two pyrimidine bases
C - cytosine T - thymine
each polynucleotide strand has a direction, explain
5’ prime end (top) 3’ prime end (bottom)
what is the DNA base sequence
5’ ACTG 3’
structure o f bases and double helix only allows pairing of…. and …. and ….. and ….
A:T C:G
what bonds are present in A:T
2H-bonds
what bonds are present in C:G
3H-bonds
base pairings only possible if the DNA strands run….
antiparallel
3 base pairing rules
- automated and self directed 2. reversible 3.is exact
how is DNA (genetic information) replicated
one strand can act as template and through base pairing another ‘complementary strand can be made this requires the involvement of DNA polymerase
what are genes
the sections of DNA that encode specific functional gene products
what are exons
stretches of DNA that code for amino acid sequences
what are introns
parts of DNA that dont code for amino acid sequences
what is a codon
a series of three nucleotides which code fro a specific amino acid
what is the start codon
ATG
what are the stop codons (3)
TAG
TGA
TAA
what do muttions in proteins arise from
changes in DNA sequence
types of changes in DNA sequence (base mutations) (4)
mid-sense substitution
silent substitution
missense deletion
nonsense insertion
explain mis-sense substitution
one of the bases in a protein is changed to a different one, resulting in the formation of a completely different amino acid. no subsequent codons are affected.
explain silent substitution
a base in a codon is replaced with a different base, but this results in no change to the amino acid produced. subsequent codons are not affected.
explain missense deletion
a base in a codon is deleted, resulting a change in all subsequent codons but only a change in the amino acid produced from that codon
explain nonsense insertion
a base is inserted into a codon sequence, resulting in a change of all subsequent codons, and therfore all subsequent amino acids produced
base mutations can potentially change ….
protein structure and function
