Unit 1 DNA and the Genome Flashcards
Eukaryotes
Organisms in which cells contain membrane bound organelles (such as the nucleus, mitochondria and chloroplast).
Prokaryotes
Organisms lacking membrane organelles, ( the word prokaryote mean before the nucleus).
They are the oldest life forms and most numerous and widespread.
DNA organisation in prokaryotes
They have a single circular double stranded chromosome, tightly packed to form a nucleotide. Further smaller rings of DNA which carry extra non-essential genes, this is called a plasmid.
DNA organisation in eukaryotes
All have linear chromosomes in their nucleus.
Eukaryotes also have circular chromosomes out with the nucleus, in mitochondria and chloroplast.
DNA packaging in eukaryotes.
One strand of DNA is several thousand times longer than the cell it belongs to.
It is essential that the DNA is organised in such a way that a chaotic tangle of strands in the nucleus is avoided.
Yeast cells
Yeast is a special example of a eukaryote.
It has a nucleus and linear chromosomes packaged with histones, it also contains plasmids, making it a useful target for genetic engineering.
Histones
The DNA double helix is tightly coiled and packaged with associated proteins, called histone proteins.
The DNA can be tightly wrapped around these proteins, but it can be unwound again when required to do so. Such as cell division.
Bacteria cell profile
Prokaryote, only plasmids present.
Yeast cell profile
Eukaryote, nucleus present, mitochondria present and plasmids present.
Palisade mesophyll cell
Eukaryote, nucleus present, mitochondria present, chloroplast present.
Cheek cell
Eukaryote, nucleus present, mitochondria present.
Nucleus chromosome type
Linear
Mitochondria chromosome type
Circular
Chloroplast chromosome type
Circular
