Chromosomes and DNA replication

avery is super good at biology 😍

prokaryote

no nucleus, no membrane bound organelles, DNA is in cytoplasm, circular DNA

Eukaryote

DNA is more complicated, DNA is in the nucleus in the form of chromosomes

DNA

molecules are long, to fit in the cell the DNA molecule must be folded

chromosome structure

packed tightly, human cell contains more than 1 meter of DNA

eukaryotic chromosomes

chromatin (DNA and protein), this forms a bead like structure called a nucleosome

helicase

separates the double helix (creating replication fork)

single-standed binding proteins

attaches to the strands of uncoiled helix (keeps them separated)

topoisomerase

prevents knots from forming

DNA Polymerase

adds the complementary strands

RNA Primer

tells the DNA polymerase where to attach the new nucleotide (understands where to attach)

telomerase

involved with lengthening telomeres (not in multi-cellular organisms)

ligase

holds DNA together

semi-conservative

keeping half of the old DNA strand and adding a new one = double helix

telomeres

helps prevent issues with shortening DNA (on the end of DNA strands)

leading strand

3’-5’, DNA polymerase add the nucleotides in a straight line

lagging strand

5’-3’, DNA polymerase is added in fragments

anti-parellel

3’ and 5’ tell us about what the direction of the strand is (if one 5’ is going up then the other 5’ has to be going down)

replication fork

the site where the separation and replication happens

okazaki fragments

the required fragments needed to add nucleotides to the lagging strand

when does DNA replication occur

the S phase

what is the result in DNA replication

2 double helixes

what are the steps to DNA replication

1. helicase (separates double helix)
2. single-stranded binding proteins (keeps the double helix separated)
3. topoisomerase (prevents knots from forming)
4. DNA polymerase (adds the complementary strands)