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Chapter 16


reside in nucleus. present in pairs. made of DNA and proteins. Homologs (pairs) separate during meiosis.


A funtional segment of DNA located at a certain point (locus) on a chromosome;codes for a protein.


found in nucleus. carries hereditary information. Consists of 4 nucleotides (contains a 5 carbon deoxyribose sugar, a phosphate and a Nitrogen base) 4 different nitrgoen bases.

DNA nucleotides

contains a 5 carbon deoxyribose sugar, a phosphate and a nitrogen containing base.

4 nitrogen bases

Thymine, Cytocine, Adenine and Guanine

Pyrimidine Bases

have single rings. Thymine and Cytosine.

Purine Bases

have double rings. Adenine and Guanine

Alfred Mirsky

worked with protein structure. helped prove that DNA must be the holder of hereditary information.

Erwin Chargaff

discovered that base composition of DNA varies from one species to another. But DNA always has equal amounts of Adenine and Thymine and equal amounts of Guanine and Cytosine.

Rosalind Franklin and Maurice Wilkins

Bombarded DNA with x-rays to form a picture. determined that DNA was helical, has repeating subunits, and had a sugar-phosphate backbone.

James Watson and Francis Crick

published structure of DNA. built the double helix model.


the two DNA nucleotides run in opposite directions.


one DNA strand is copied to produce 2 identical strands

Conservative Replication

A possible model of replication. 2 parental strands act as templates for 2 new strands then reassociate. This was determined to be false.

Semi-Conservative Replication

A possible model of replication. 2 parental strands act as templates for 2 new strands. Each replicated helix contains one "old" strand and one "new" strand. This was determined to be true by Messelson and Stall.

Dispersive Replication

A possible model of replication. Daughter strands are composed of old and new DNA pieces.

Origin of Replication

replication begins here.

Replication Bubble

the open area that is made when DNA begins separating for replication.

Antiparallel Elongation

DNA can only be replicated in a 5 prime to 3 prime direction.

Okazaki Fragments

to replicate "backwards", pieces on the lagging strand are made in the 5 prime to 3 prime direction and those pieces are called...


"unzips" DNA.


works ahead of the helicase to relieve tension on the double helix. It does this by cutting the sugar-phosphate backbone, swiveling it and reattaching it.

Single-Strand Binding Proteins

stabilizes the template DNA so they do not reattach.


adds RNA primer to strands so DNA bases can be added to make the new DNA molecule.

RNA Primer

leading strand only needs one primer from the origin of replication. Lagging strand needs a new primer for each Okazaki Fragment.

DNA Polymerase III

attaches nucleotides to form the new DNA strand.

DNA Polymerase I

removes the primer and adds one or more nucleotides.

DNA Ligase

links sugar phosphate backbone of the Okazaki Fragments together.

Proofreading Enzymes

proofread the DNA. 130 types identified in humans. 1 in 100,000 are mispaired and then corrected. DNA polymerases also double check base pairing.


Repeated DNA sequences at the ends of eukaryotic chromosomes.


humans have this repeated 100-1000 times at the ends to protect the ends of the DNA. carries no genetic information. is just there to protect the ends.


this enzyme lengthens the telomeres back to their original length.

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