Download 5 Chapter 12 DNA RNA

DNA and RNA
1
DNA
•  Stores and transmits
genetic information
•  Polymer of
nucleotides
–  Deoxyribose
–  Phosphate group
–  Nitrogenous base
2
Structure of DNA
Adenine
Thymine
Cytosine
Guanine
Phosphate
Group
Deoxyribose
Nucleotide
•  DNA has four
Nitrogen Bases
• 
• 
• 
• 
Adenine
Thymine
Cytosine
Guanine
3
Chromosomes
•  Chromosomes are
cellular structures that
contain genetic
information that is
passed from one
generation to the next
–  Composed of
Chromatin
•  Which is made up of
DNA and a protein
4
•  Two identical parts of
a chromosome called
chromatids, are
attached to one
another at a
centromere
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Replication -----•  During replication
(prior to cell division)
the DNA molecule
unzips into two
strands
•  Each strand serves
as a template for the
attachment of
complimentary
nucleotides
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RNA
• 
There are three major differences
between RNA and DNA
1.  RNA contains ribose instead of deoxyribose
2.  RNA is usually singled stranded
3.  RNA contains the nitrogenous base uracil instead
of thymine
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Transcription
DNA molecule is copied into a complimentary strand of
RNA
•  RNA polymerase unzips
DNA and begins to
synthesizes mRNA
•  Carries the code out of
the nucleus into
cytoplasm
•  The DNA code is
transferred to mRNA
•  This is known as mRNA
•  During transcription
adenine is bonded to
uracil not thymine (as in
replication)
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Translation
•  mRNA binds to the ribosome where
ribosomal RNA is found
•  Amino acids are picked up by tRNA in the
cytoplasm and carried to mRNA
•  Anticodons in tRNA attach to proper
codons in mRNA
•  mRNA acts like a pattern for protein synthesis
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MUTATIONS
l 
Mutations are changes in genetic material
– 
10
Two Types
–  Chromosomal Mutations
–  Gene Mutations
Chromosomal Mutation
l 
l 
A Mutation involving a segment of a
chromosome, an entire chromosome, or
many chromosomes
There are four types of mutations involving
the structure of a chromosome:
l 
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Deletion, duplication, inversion, translocation
Chromosomal Mutation
l 
Deletion –
– 
l 
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Loss of part of the
chromosome
Duplication– 
l 
Segment of chromosome
is repeated
Inversion– 
l 
Chromosome is
orientated in reverse
Translocation– 
Segment breaks off and
attaches to a nonhomologous
chromosome (same
time)
Chromosomal Mutation
l 
Chromosomal Mutations involving whole
chromosomes is known as nondisjunction
– 
Failure of homologous chromosomes to separate
during meiosis
Resulting in extra chromosome in one cell and a missing
chromosome in another (involving one chromosome)
l  Polyploidy can result when entire sets of chromosomes
are involved
l 
13
Gene Mutation
l 
A Mutation that involves just one gene
– 
Can involve many nucleotides or a single
nucleotide within a gene
– 
Point Mutation – affects one nucleotide
Frameshift Mutation – a single base is inserted or
deleted, changing the polypeptide produced by
gene
– 
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Gene Regulation
l 
Lac Operon – group of genes that turn genes
on or off (lactose)
– 
l 
Eukaryotic cells more complex
– 
– 
– 
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Turned of by repressor protein that blocks
transcription
enhancers
Promoter Sequences
TATA box – helps position RNA polymerase