Nucleic Acid Structure, DNA Replication, and Chromosome Structure

Information

Replication

Transmission

Variation

Four criteria that genetic material must meet

Information

Criteria where genetic material must hold the information to produce an entire organism

Replication

Criteria where genetic material must accurately be copied

Transmission

Criteria where genetic material must be able to be passed from parent to offspring

Variation

Criteria where difference in genetic variation must account for the variation in living organisms

Protein has a more complex structure than DNA

Why protein was originally assumed to contain genetic material

Phosphodiester Bond

Bond between the sugar and phosphate groups of nucleotides

Negative

The overall charge that the phosphate group gives DNA

Cytosine and Thymine

Pyramidines (2)

Adenine and Guanine

Purines (2)

Cytosine and Guanine

Adenine and Thymine

Complementary base pairs

2, 3

Adenine and thymine are held together by ___ H-bonds, while cytosine and guanine are held together by _____ H-bonds

2, 3.4

DNA is about ____ nm across and _____ nm per complete spiral

Around 10

The number of base pairs per spiral

Major Groove

Where most proteins will bind to act on DNA

Conservative, Semi-Conservative, Dispersive

The three potential models of DNA replication

Meselson and Stahl’s Replication Experiment

Experiment that disproved the conservative and dispersive models and determined that DNA is semi-conservative

Semi-Conservative Model

DNA replication model where each DNA double helix is composed of one parental strand and one daughter strand

Conservative Model

DNA replication model where each DNA double helix is made of either two parental or two daughter strands

Dispersive Model

DNA replication model where each double helix is composed of a mixture of a parental and daughter strand

DNA Helicase, DNA Topoisomerase, Single strand binding protein

Enzymes that prepare for DNA replication (3)

DNA Helicase

DNA replicating enzyme that unwinds the double helix, binds to one template strand traveling from the 5’ to 3’ end, uses ATP to break hydrogen bonds between base pairs, and causes “supercoils” to form ahead of the replication fork

DNA Topoisomerase

DNA replicating enzyme that relaxes the supercoils that form from the unwinding of DNA

Single Strand Binding Protein

DNA replicating enzyme that bind to the single strands of DNA to keep them apart

DNA Primase, DNA Polymerase

Enzymes that synthesize DNA (2)

DNA Primase

DNA synthesizing enzyme that attaches a complementary sequence of RNA (RNA primer) to the template strand at the start site of replication

DNA Polymerase

DNA synthesizing enzyme that covalently links nucleotides together to form phosphodiester bonds and synthesizing a new complementary strand starting at the RNA primer, Reads the template strand in the 3’ to 5’ direction, Generates the new complementary strand in the 5’ to 3’ direction, Has a proofreading function that removes mismatched base pairs

Leading Strand

Daughter strand that forms in the same direction as the forming replication fork, Forms in one continuous strand

Lagging Strand

Daughter strand that forms in the opposite direction of the forming replication fork, Forms in Okazaki fragments

Okazaki Fragments

Small segments that form on lagging strands that are later put together to form a continuous strand due to the fact that DNA polymerase only synthesizes DNA in the 5’ to 3’ direction and the two template strands of DNA are antiparallel

DNA Ligase

Covalently bonds nucleotides together

Telomeres

The ends of linear chromosomes that exist due to the inability of polymerase to attach at the very ends

3’ Overhang

Region at the end of the telomere because polymerase can only build a polymer in the 5’ to 3’ direction

Telomerase

Enzyme that extends to the end of the chromosome

Chromatin, Nucleosomes, 30nm fiber

The varying degrees in which chromosomes exist (3)

Chromatin

Complex of DNA and protein that make up eukaryotic chromosomes

Nucleosomes

Repeating structural units composed of 146-147 base pairs wrapped around an octomer of histone proteins

30nm Fiber

Compaction of nucleosomes together

Nuclear Matrix

Filamentous protein network that binds the 30nm fiber to form radial loop domains composed of a nuclear lamina which lines the internal nuclear membrane and the matrix that radiates inside the nucleus

Euchromatin

The loosely compacted chromatin where most gene activity is located

Heterochromatin

The highly compacted where very little gene activity is located (centromeres + telomeres)