DNA Review & Chromosomes
Jan 03, 2016
DNA Review& Chromosomes
DNA StRucture• Rosalind Franklin-
Took first x-ray crystallography pictures of DNA
• Watson & Crick – used Franklin’s pictures to come up with double helical model of DNA
DNA is Genetic Material
• DEOXYRIBONUCLEIC ACID
– Controls protein production in cells
– Made up of many genes which control traits
DNA structure• Made up of units called
NUCLEOTIDES
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DNA structure
Remember that DNA has 2 strands
Each strand is COMPLEMENTARY to the other
Complementary Strands• If we know the DNA sequence of one
strand, we can predict the DNA sequence of it’s complement
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C C GG A AT T
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C
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CPO4
A
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A
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T
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T
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G
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G
Review• Write the complementary strand
sequence for the following:
ATTCGACTACCTG
TAAGCTGATGGAC
Identify its pair
Cytosine pairs with: GUANINE
Adenine pairs with:
THYMINE
DNA Folding• DNA strands must fold up into a
smaller package before cellular division can occur.
• Histones are proteins that the DNA strand wraps around to form condensed packages.
• This complex of proteins and DNA is called chromatin.
• https://www.youtube.com/watch?v=gbSIBhFwQ4s
Chromosomes• These final
packages of condensed DNA are known as chromosomes.
To be Genetic Material• Requirements:
1. Able to store and pass information from one generation to the next
2. The stored info is responsible for traits
3. Must be easily replicated with minimal errors
Genes• DNA is the blueprint of
the body, because it tells the cells what proteins to make.
• A section of a chromosome with a particular sequence of DNA that codes for a specific protein(s) is called a gene.
• These proteins determine traits.
Alleles• Most genes have at least two
different proteins that can determine traits.
• Different sequences of DNA that code for different proteins of the same trait are called alleles.
TACTTGCATCGGTCAATCATGAACGTAGCCAGTTAG
TACTTGCCTGAATCAATCATGAACGGACTTAGTTAG
Blue eyesBrown eyes
Mutation• Alleles arise from genetic
mutation.
• A mutation is the change in the DNA sequence for a particular gene.
• There are two main types of mutations: – Point– Frame shift
Point Mutation• A point mutation is when a single
nucleotide of the sequence is miscopied during DNA replication.
TACGTTATAATC TACGTAATAATC
Substitution• The miscopy can cause a new
protein to be produced.
TACGTGATAATC
AUGCACUAUUAG
TACGTTATAATC
AUGCAAUAUUAG
Met-His-Tyr Met-Gln-Tyr
Silent Mutation• The miscopy can also have no
affect on the protein produced.
TACGTGATAATC
AUGCACUAUUAG
TACGTAATAATC
AUGCAUUAUUAG
Met-His-Tyr Met-His-Tyr
Frame shift• Frame shift is when the bases
shift and codons change.
• There are two types of frame shift– Deletion– Insertion
TAC GTG ATA ATC AC GTG ATA ATC ACG TGA TAA TC
TAC GTG ATA ATC A TAC GTG ATA ATC ATA CGT GAT AAT C
Insertion• Insertion is when a nucleotide is
put in the middle of the DNA sequence.
• This causes all the nucleotides to shift producing mostly new codons.
TAC GTG ATA ATC A TAC GTG ATA ATC ATA CGT GAT AAT C
Deletion• Deletion is when a nucleotide is
removed from the middle of the DNA sequence.
• Again this causes all the nucleotides to shift producing mostly new codons.
TAC GTG ATA ATC ACG TGA TAA TCAC GTG ATA ATC