Chapter 16: The Molecular Basis Of Inheritance

Front 1

Double Helix

Back 1

Structure of DNA. Two strands which are anti parallel

Front 2

Antiparallel

Back 2

DNA's two sugar-phosphate backbones subunits run in opposite directions. Always run 5 prime to 3 prime.

Front 3

Semi Conservative

Back 3

When DNA replicates each of the two daughter molecules will have one new strand and one old strand.

Front 4

Origin of Replication

Back 4

The replication of chromosomes begin at particular sites called origins of Replication. Made of short stretches of DNA having a specific sequence of nucleotides.

Front 5

Replication Fork

Back 5

At the end of each bubble, a Y shaped region where the parental strands of DNA are being unwound.

Front 6

Steps of DNA Replication

Back 6

Step 1: Proteins that initiate DNA replication recognize the sequence and attach to DNA separating the two strands and opening up a replication bubble.
Step 2: Helicases unwind the double helix at the replication forks making them available as template strands.
Step 3: Single-strand binding proteins bind to the unpaired DNA strands, keeping them from repairing.
Step 4: Initial nucleotide is created as a primer. This RNA primer is then synthesized by primase.
Step 5: The completed primer, generally 5-10 nucleotides long, is thus base-paired to the template strand. The new strand will start from the 3' end of the RNA primer.
Step 6: DNA polymerase III adds the bases to the 3' end of the strand.
Step 7: DNA runs into the next RNA primer.
Step 8: DNA polymerase I removes RNA bases, replaces them with DNA Step 9:DNA ligase joins two strands.

Front 7

Helicases

Back 7

Enzymes that unwind the double helix.

Front 8

Single-Strand Binding Proteins

Back 8

Bind to the unpaired DNA strands, keeping them from repairing.

Front 9

Topoisomerase

Back 9

The untwisting of the double helix causes tighter twisting and strain ahead of the replication fork. This enzyme helps relieve the strain by breaking, swiveling, abd rejoining DNA strands.

Front 10

Primer

Back 10

The initial nucleotide chain that is produced during the DNA synthesis. Made of a short stretch of RNA.

Front 11

Primase

Back 11

Synthesizes the primer by adding more RNA nucleotides one at a time, using the parental strand as a template.

Front 12

DNA Polymerase

Back 12

Catalyze the synthesis of new DNA by adding nucleotides to a preexisting chain.

Front 13

Leading Strand

Back 13

DNA strands made by DNA polymerase III remaining in the replication fork and adding nucleotides in the mandatory 5' to 3'. only one primer is required for DNA polymerase III to synthesize the entire leading strand.

Front 14

Lagging Strand

Back 14

DNA polymerase must work in a 5' to 3' so it moves away from the replication fork. Occurs at the same rate in which the leading strand is made. Synthesized discontinuously as a series of segments.

Front 15

Okazaki Fragments

Back 15

Segments of the lagging strand. Named after the Japanese scientist who discovered them. Each fragment must be primed separately. DNA polymerase I cannot join the final nucleotide of the adjacent fragment. Another enzyme (ligase) must complete the strand.

Front 16

DNA Ligase

Back 16

Joins the sugar-phosphate backbones of all the Okazaki fragments into a continuous strand.

Front 17

Mismatch Repair

Back 17

Sometimes nucleotides sometimes evade proofreading by a DNA polymerase. In a mismatch repair, other enzymes remove and replace incorrectly paired nucleotides that have resulted from replication errors.

Front 18

Nuclease

Back 18

DNA-Cutting enzyme and the resulting gap is then filed with nucleotides using the undamaged strand as a template.

Front 19

Telomeres

Back 19

Eukaryotic chromosomal DNA molecules have special nucleotides called telomeres at their ends. Do not contain genes. Two protective functions. 1) Prevent the staggered ends of the daughter molecule from activating the cell's systems for monitoring DNA damage. 2) Kind of buffer zone that provides some protection against the organisms genes shortening. Postpone erosion.