Download DNA Notes HB

DNA Review
& Chromosomes
DNA StRucture
• Rosalind FranklinTook 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
PO4
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
C
A
G
A
T
A
T
PO4
C
PO4
T
PO4
G
PO4
PO4
PO4
G
PO4
PO4
C
T
G
A
C
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
Review
• Write the complementary strand
sequence for the following:
ATTCGACTACCTG
TAAGCTGATGGAC
Purines & Pyrimidines
• Purine – Base that has 2
carbon/nitrogen rings
– Adenine & Guanine
• Pyrimidine – Base that has 1
carbon/nitrogen ring
– Cytosine, Thymine, & Uracil
Purine
Pyrimidine
Identify its pair
Cytosine pairs
with:
GUANINE
Adenine pairs
with:
THYMINE
Purine & Pyrimidine
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
• Chromatin will
continue to
condense.
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.
TACTTGCATCGGTCAATC TACTTGCCTGAATCAATC
ATGAACGTAGCCAGTTAG ATGAACGGACTTAGTTAG
Brown eyes
Blue 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
TACGTTATAATC
AUGCACUAUUAG
AUGCAAUAUUAG
Met-His-Tyr
Met-Gln-Tyr
Silent Mutation
• The miscopy can also have no
affect on the protein produced.
TACGTGATAATC
TACGTAATAATC
AUGCACUAUUAG
AUGCAUUAUUAG
Met-His-Tyr
Met-His-Tyr
Frame shift
• Frame shift is when the bases
shift and codons change.
TAC GTG ATA ATC
TAC GTG ATA ATC
AC GTG ATA ATC
ACG TGA TAA TC
A TAC GTG ATA ATC ATA CGT GAT AAT C
• There are two types of frame shift
– Deletion
– Insertion
Insertion
• Insertion is when a nucleotide is
put in the middle of the DNA
sequence.
TAC GTG ATA ATC
A TAC GTG ATA ATC ATA CGT GAT AAT C
• This causes all the nucleotides to
shift producing mostly new
codons.
Deletion
• Deletion is when a nucleotide is
removed from the middle of the
DNA sequence.
TAC GTG ATA ATC
AC GTG ATA ATC
ACG TGA TAA TC
• Again this causes all the
nucleotides to shift producing
mostly new codons.