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Biology Chapters 14, 15, 16


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An enzyme that untwists the double helix of DNA at the replication forks.
Sngle-Strand Binding Protein
During DNA replication, molecules that line up along the unpaired DNA strands, holding them apart while the DNA strands serve as templates for the synthesis of complementary strands of DNA.
An enzyme that joins RNA nucleotides to make the primer.
DNA Ploymerase
An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.
DNA Ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3’ end of a new DNA fragment to the 5’ end of a growing chain.
An enzyme that hydrolyzes DNA and RNA into their component nucleotides.
An enzyme that catalyzes the lengthening of telomeres. The enzyme includes a molecule of RNA that serves as a template for new telomere segments.
2 things DNA must do
1. Must be able to replicate (duplicate)

2. Code for specific traits
3 hypothesis of DNA replication
1. Conservative - one cel gets parent double helix, the other cell gets new double helix

2. Semi- conservative
Each cell gets a double helix with one strand from the parent, the other strand is new

3. Dspersive
Each cell gets a double helix with both strands contaning some parent and some new DNA

the correct hypothesis is Sem-conservative where the double helix hydrogen bond is broken and each cell gets one strand of DNA from the parent.
Basic Principle of DNA
2 strands are complementary

each strand acts as a template for building a new strand

DNA replciation happens during the S phase of the cell cycle
Franklins conclusions
DNA is composed of 2 antiparallel sugar-phosphate backbones with nitrogenous bases paired in the molecules interior

Antiparallel means the 2 DNA strands rund in opposite directons

Base pairing rules

The nitrogenous bases are paired adenine with thymine and cytosine with guanine - the 2 strands are complementary (matching)
Bonds formed in DNA
Adenine and Thymine form 2 bonds

Cytosine and Guanine form 3 bonds
the most celebrated molecule of our time

Heredity information is encoded in the chemical language of DNA and reproduced in all the cells of the body

It is the DNA program that directs the development of many different types of traits

The role of DNA in heredity was first worked out by studying bacteria and the viruses that infect them.
results from the fertilization of gametes in which nondisjuncton occured. Is a condition in which offspring have a changed number of a particular chromosome.

If a zygote has 3 copies of a particular chromosome it is Trisomic

If a zygote has 1 copy of a particular chromosome it is monosomic
Pairs of homologous chromosomes or sister chromatids do not separate during meiosis.

Gametes contain 2 copies or no copies of a particular chromosome
Linked Genes
tend to be inherited together because they are located near each other on the same chromosome
Linkage affects inheritance of two different genes
linked genes do not assort independently; they are close togther on the same chromosome (non-medelian)

Unlinked genes assort independently; either they are on separate chromosomes or are far apart on the same chromosome.

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