DNA, genes And Chromosomes Flashcards
How is DNA stored in eukaryotic cells?
Double helix, linear DNA molecules that exist as chromosomes, each made up of of long DNA molecule and associated proteins. Chromosomes are found in nucleus.
As DNA molecule is really long it has go be wound around proteins called histones. DNA (and protein) folded/coiled into chromosome.
How is DNA stored in prokaryotic cells?
Prokaryotes also carry DNA as chromosomes — but the DNA molecules are shorter and circular.
The DNA isn’t wound around proteins/ histones — it condenses to fit in the cell by supercoiling.
(Circular chromosome to coiled chromosome to supercoiled to fit into cell)
Have plasmids
DNA in mitochondria and chloroplasts?
Have their own DNA in eukaryotic cells but same properties as DNA in prokaryotic cells (shorter, circular no histone proteins, no nucleus) but dont have plasmids.
What is a gene?
A sequence of DnA that codes for a polypeptide or a functional RNA. (RNA molecules other than mRNA eg tRNA or rRNA) Sequence of amino acids in a polypeptide forms the primary structure of a protein
What is a locus?
Location of a gene on a chromosome (doesn’t change between organisms within same species)
What is a DNA triplet?
A sequence of 3 DNA bases in a gene that code for a specific amino acid
What is the genetic code?
The sequence of base triplets in mRNA which code for specific amino acids
What are the three features of the genetic code?
Universal- the genetic language in all living organisms. (GGT codes for glycine in all living organisms)
Non overlapping- each DNA triplet and gene is separate from each other
Degenerate- The same amino acid can be coded for by more than one triplet
What is the genome?
The complete set of genes in a cell/organism
What is a proteome?
The full range of proteins that a cell is able to produce
In eukaryotes a lot pf the nuclear DNA doesn’t code for polypeptides what does it code for?
Functional RNA
What are sections within a gene that dont code for polypeptides or amino acids
Introns. (Removed during protein synthesis so don’t affect amino acid order). Prokaryotic cells don’t have introns
What’s an exon?
Sequence within gene that does code for amino acids
When does DNA not code for proteins/ polypeptides or functional RNA)
Regions of non coding multiple repeats outside/between genes. DNA sequences that repeat over and over
