Eukaryotic DNA Flashcards
what does DNA stand for ?
Deoxyribonucleic acid
What does RNA ?
Ribonucleic acid
What is the role of DNA ?
respiratory of genetic information
How long is DNA in human cells ?
- roughly two meters of DNA
what is the size of the nucleus ?
5μm in diameter (2-10 μm)
what is the DNA paking accomplished by ?
specialised proteins that bind to the DNA and fold it
what do the proteins that package DNA generate ?
- a sereis of organised coils and loops = higher lvel if organisation
- prevent the DNA from becoming an unmagegeable tangle
what is the most important fuction of DNA ?
- carry genes, because this info specifies all RNA molecules and protein that mame up an organism
what does a chromosome consist of ?
- single, long linear DNA molecule
- they are folded and packed by proteins into a more compact structure
what processes are chromososmes required for ?
- Gene expression
- DNA replication
- DNA repair
what is the name of the protein that keeps chromososmes bound together ?
Chromatin
How is DNA in Viruses ?
- nacked DNA
- Protein free packing
How is DNA in Prokaryotes ?
- Partially condensed
- Some proteins bind DNA
How is DNA in Eukaryotes ?
- highly condensed
- many proteins bind DNA
How are chromosomes/DNA in bacteria?
- circular
- condensed by supercoiling
- nucleoid-associated proteins holds their structure
- DNA ot wrapped arounf protein like in Eukaryotes
What is the process of DNA condensation in eukaryotes ?
- Chromatin formation
- Fimalment formation
- Scaffold formation
- Metaphase chromosome formation
What happens in chromatin formation ?
- coils of DNa are wrapped around a core of DNA binding proteins (histones)
- resembles beads on a string, each bead is called a nucleosome
- 10nm in diametre and 147 bp of DNA
what happens in filament formation ?
- the beads on a string chromatin structure of DNA can only be seen in a low salt-buffer
- Dna is comdemsed further to form a ribbon-like structure called FILAMENT
- 30nm ribbon
- reduced lengh of DNA by 100x
what does the Linker histone (H1) regulates ribbon formation ?
- linker = the region of DNA between nucleosomes
- specilalised histone (H1) binds to linker DNA
- H1 no present within nucleosomes
- binding H1 regulates formation of the ribbon structure
what does the Linker histone (H1) regulates ribbon formation ?
- linker = the region of DNA between nucleosomes
- specilalised histone (H1) binds to linker DNA
- H1 no present within nucleosomes
- binding H1 regulates formation of the ribbon structure
what happens in the scaffold formation ?
- 30nm filament is further looped around and anchored to the chromosome scaffold at specific points by specialised proteins
- loosely condensed structure consisting of 300nm loops is as well as a more condensed struccture of 700nm loops
what happens in metaphase chromososme ?
- most compact phase of DNA condensation is only seen during mitosis
- compact chromosomes lines up at the equator of the cell and become visisble under the microscope
what is DNA supercoiling ?
- Twisting of DNA likea rope
What does supercoilling do ?
- reduce the space required for DNA packaging (efficient DNA storage)
what are the 2 types of supercoilling ?
positive and negative supercoilling
what is positive supercoiling ?
- when DNA is overwound
- they are formed when they are unwunded by helicase
- enzyme (DNA gyrase) to reduce the strains
what is negative supercoiling ?
- underwounded DNA
- most DNAs are negatively supercoiled by enzymes called TOPOISOMERASES
