DNA, Genes And Chromosomes Flashcards
Describe the DNA of prokaryotic cells
- DNA molecules are short
- circular
- not associated with proteins
Describe the DNA of eukaryotic cells
- DNA molecules are very long
- linear
- associated with proteins, called histones
Compare the DNA of prokaryotic and eukaryotic cells
- DNA molecules of eukaryotic cells are very long, linear and associated with proteins, called histones whereas DNA of prokaryotic cells are short, circular and not associated with proteins
Describe the DNA of mitochondria and chloroplasts
- short
- circular
- not associated with protein
Define gene
- A base sequence of DNA that codes for a specific polypeptide or a functional RNA
What does a gene code for?
- the amino acid sequence of a polypeptide
- a functional RNA
What is a locus?
- position of a gene on a chromosome
What is a sequence of three DNA bases called?
- triplet
What do DNA bases code for?
- a specific amino acid
What are the features of the genetic code?
- Degenerate
- Universal
- Non overlapping
Define polypeptide
- A sequence of amino acids joined by peptide bonds
What is a histone?
- proteins that surround DNA
What are introns?
- non coding sequence of DNA
What does it mean when genetic code is degenerate?
- more than one triplet codes for one amino acid
What does it mean when genetic code is universal?
- a triplet always codes for the same amino acid in all organisms
What does it mean when genetic code is non overlapping?
- Each base only appears in one triplet base sequence
- adjacent triplets do not overlap
What are the coding sequence of DNA called?
- exons
What is the advantage of the genetic code being degenerate?
- if a point mutation occurs, even though the triplet of bases will be different, it may still code for the same amino acid and therefore have no effect
Why is the genetic code being universal an advantage?
- means genetic engineering is possible eg. Inserting the human gene for insulin into bacteria
Why is the genetic code being non overlapping an advantage?
- if a point mutation occurs, it will only effect one codon and therefore one amino acid
