Booklet 1 Model Answers Flashcards
What is the difference between a nucleotide and nucleic acid?
A nucleotide is a monomer
Nucleic acid is the polymer
Replication of DNA
Double helix unzips
Catalysed by helicase
hydrogen bonds break
Free DNA nucleotides in the nucleus complementary base pair with exposed bases on both strands
DNA polymerase joins nucleotides together in the new strands ( catalysed formation of ester bonds )
This results in the formation of identical strands
What does semi conservative replication mean?
two new molecules form which are exact copies of the original strand
One of the chains in each new molecule was present in the original molecule
The other chain is newly synthesised from free nucleotides
Key features of DNA
Stable so can be passed on from generation to generation
Hydrogen bonds between strands are easily broken for DNA replication
Large so can carry a lot of genetic information
Base pairs are contained within the helix and are protected from corruption by the strong sugar phosphate backbone
Complementary
Base pairs allow the synthesis of an identical daughter molecule
Important features of the genetic code
It is not overlapping ( specific start and stop codons)
It is degenerate ( some amino acids are coded for by one or mo codon
It is read in only one direction
It is universal - the same code applies to all organisms
Definition of a gene
A section of double stranded DNA coding for a single polypeptide
Introns
Non coding sections of DNA
Definition of an allele
One alternative form of a gene
Definition of a locus
The position of a particular allele on a chromosome
Definition of a triplet code
Three bases in a particular sequence code for one amino acid
If you are given the number of amino acids and are asked to calculate the minimum number of DNA bases needed. What would you do?
X 3
Relationship between DNA and protein
DNA has a specific sequence of bases
Arranged into specific codons (triplets)
Each codon codes for one amino acids he ribosome reads the code and arranges the amino acid in the correct order (determined by the DNA sequence)
Peptide bonds form between amino acids making a polypeptide chain
This is then folded to make a protein with specific tertiary structure
