Download DNA - scombskhs

Deoxyribonucleic Acid - found in all
living organisms!
Found in every type of cell.
Chromosomes are strands of DNA and protein.
 Genes are located on each chromosome.
 A gene is a segment of DNA that codes for the
production of a particular protein.
 The protein produced determines the trait.

Ex. Eye color, earlobe shape, toe shape, etc.
 Discovered
by James Watson & Francis Crick,
won the Nobel Prize for this work – 1953.
 Described the structure as a double helix or
“twisted ladder” made up of combinations
of nucleotides.
 Nucleotide
– composed of a nitrogen base, a
sugar and a phosphate group.
* There are 4 N bases:
1. Adenine – A
2. Guanine – G
3. Thymine – T
4. Cytosine - C
nucleotide
 The
sides of the ladder
are made up of sugar
and phosphate groups.
•
The nitrogen bases make
up the rungs (steps).
* The N bases are held
together by weak H bonds.
•
Base Pair Rule – the bases are said to be
complementary, ie. they
pair in a specific manner:
•
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Adenine (A) pairs with Thymine (T) “sticks”
Guanine (G) pairs with Cytosine (C) “curves”
 The
DNA molecule of the smallest virus
contains 5,000 nucleotides.
 In a human cell, all 46 chromosomes contain
more than 5 billion nucleotides.
 The unique sequence of the nucleotides
controls the production of proteins and
individual variation.
 No two individuals have the same DNA
sequence (exception – identical twins and
clones).
 During
interphase of the cell cycle,
DNA replicates (copies) itself.
•
Replication insures that
each new cell will have a
complete copy of the
genetic code.
Steps of replication:
http://www.youtube.com/watch?v=zdDkiRw1PdU
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•
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1. DNA molecule acts like a zipper. DNA helicase
unzips the molecule by breaking the H bonds
between the N bases.
2. Each side of the unzipped strand acts like a
template for building a complementary strand.
3. Free floating nucleotides will pair with its’
complementary base. IE. A – T ; C – G.
4. The enzyme DNA polymerase proofreads the
replicated molecules.
5. Each completed DNA molecule now has one “old”
strand and one “new” strand.
 DNA
controls the synthesis (making) of proteins
from amino acids.

Remember: 1.proteins are the basic building blocks
of all living things.
2.DNA is only found in the nucleus.
Problem:
•
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proteins are made in the ribosomes.
ribosomes are found in the cytoplasm.
DNA cannot leave the nucleus.
Solution:
•
RNA, ribonucleic acid.
 RNA

DNA contains sugar deoxyribose.
 RNA

contains the sugar ribose.
is a single stranded molecule.
DNA is a double stranded molecule.
 RNA
nitrogen bases are Adenine,
Guanine, Cytosine and Uracil
(G–C;A–U)

DNA bases are Adenine, Guanine, Cytosine and
Thymine ( A – T ; G – C )
3

types of RNA:
mRNA – messenger RNA


tRNA – transfer RNA


Ribbon-like
Clover-leaf shape
rRNA – ribosomal RNA

Found in the ribosome