genetic information Flashcards
how is DNA stored in eukaryotes
long
linear
associated with proteins (histones)]
tightly coiled into chromosomes
how is DNA stored in prokaryotes
short
circular
not associated with proteins
how is DNA stored in chloroplasts and mitochondria
short
circular
not associated with proteins
describe the features of DNA which make it a stable molecule
- two strands with specific base pairing
- large no. of hydrogen bonds between strands
- helix/coiling reduces chance of molecular damage
- strong sugar-phosphate backbone
describe the molecular structure of DNA
- Long polymer of nucleotides;
- composition of a nucleotide (pentose sugar, phosphate and N containing base)
- 4 bases named (A, T, C and G) (Uracil (U) is a base in RNA that replaces T), A, G are purine bases (2 ring structure) T, C and U are pyrimidine bases (single ring structures)
- sugar-phosphate ‘backbone’;
- two (polynucleotide) strands;
- specific base-pairing;
- example e.g. A–T / C–G; there are 2 H bonds between A/t and three H bonds between C/G
- hydrogen bonding between bases
explain how the structure of DNA is related to its function
6
- sugar - phosphate backbone gives strength (phosphodiester bonds)
- (coiling gives) compact shape;
- sequence of bases allows information to be stored;
- long molecule stores large amount of information;
- information can be replicated/complementary base pairing;
- (double helix protects) weak hydrogen bonds/double helix makes molecule stable prevents code being corrupted;
- chains held together by weak hydrogen bonds;
- chains can split for replication / transcription
- Complementary base pairing enables information to be replicated/transcribed
- Many hydrogen bonds together give molecule stability;
- Hydrogen bonding allows chains to split for replication/transcription OR molecule unzips easily for replication / transcription.
what are genes
sequence of DNA
what do genes code for
amino acid sequence of a polypeptide
functional RNA
what does a gene occupy and what is this called
a fixed position
locus
what does a sequence of triplets code for
sequence of amino acids
describe the nature of the genetic code
degenerate
-same amino acid can be coded for by more than one triplet
universal
-same specific triplet codes for same specific amino acid in all living organisms
non-overlapping
-each base can be used only once and in one triplet , in a sequence
Explain why, in eukaryotes, much of the DNA doesn’t code for polypeptides.
- Between genes…
- Non-coding multiple repeats
- Within genes
- Only exons code for amino acid sequences,
which are separated by one or more non-coding sequences, called introns
- Only exons code for amino acid sequences,
what is a locus
position of a gene
on a strand of DNA
what are genes
sections of coding DNA
what is a mutation
change in base sequence of a gene
