Review about DNA

What is the structure below called?

What are the three pieces that make up a nucleotide? Phosphate Nitrogen Base Sugar

What kinds of bonds exists between the Bases of DNA?

Watson and Crick found that DNA was in the shape of an?

Adenine always binds with______ Cytosine always binds with_____ Thymine always binds with_____ Guanine always binds with_____

Chromosomes Eukaryotes Prokaryotes Found in the nucleus DNA is found in the cytoplasm Single circular DNA molecules DNA replication begins at a single point in the chromosome & proceeds in both directions until the chromosome is replicated Eukaryotes Found in the nucleus Chromosome number varies between species DNA replication occurs at hundreds of places called replication forks

Chromosomes How much DNA in a human nucleus? What is chromatin? more than 1 meter What is chromatin? DNA tightly coiled around proteins called histones

Chromosomes How are chromosomes constructed? DNA & histones form beadlike structures called nucleosomes Nucleosomes pack with one another to form thick fibers Fibers are shortened by a system of loops & coils

Replication

Replication – General Info The exact copying of DNA Replication occurs in both directions DNA must be copied before cells divide  each daughter cell has a complete set of DNA Original strands serve as templates for new strands

Replication – General Info How it happens: Helicase (enzyme) unwinds the DNA by breaking hydrogen bonds

Replication – General Info DNA polymerase (enzyme) joins individual nucleotides to each separated strand, producing DNA molecule DNA polymerase also proofreads each new DNA strand to make perfect copies

Replication – General Info Results: 2 DNA molecules  each contains one original strand & one new strand