Unit 3: Genetics
Extras
Study Guide
Chapter 16
9
Review
The physical structure of nucleic acids such as _ANI_16,5 RNA or
was
discovered
by Watson and Crick from photos of
crystallography made by Rosalind
Franklin
.
DNA is a double
, with the sugar-phosphate backbones on the
outside
, and pairs of
bases on the _act_16&C inside.
_act_16&B Weak
bonds form between the complementary base
pairs
:
(A) always pairs with
(T), and
(C) always pairs with
(G).
The base-pairing rules are used for DNA
: each strand acts as a
for building a
strand
.
The replication occurs in three phases:
,
, and
.
Initiation
Elongation
Termination
_act_16&D
Summary: DNA replication
Base-pairing is about 99.999% accurate, an error occurs about 1 in
base pairs. DNA
can "proofread" during polymerization and replace most incorrect
nucleotides
.
Uncorrected DNA can be repaired by nucleotide
repair
.
The overall error rate is about 1 in 10
nucleotides, or 99.99999999%
accurate
.
The ends of linear eukaryotic chromosomes get
with each
round
of replication.
Each chromosome terminates in a
, that
postpones
the erosion of genes near the
ends
.
Eukaryotic
cells contain the enzyme
to
lengthen
telomeres in gametes.
Eukaryotic DNA is packaged with
proteins
to form
, which condense into visible chromosomes during mitosis.
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