Download 12-2 DNA Structure

12-2 DNA Structure
What is a Macromolecule?
DNA
Stands for DeoxyriboNucleic Acid
Ribose
(Sugar)
Without
Oxygen
Macromolecule
classification -polymer of
nucleotides
A large molecule that is created by
linking smaller subunits.
DNA
● Shape of a double
helix
● Made of repeating
subunits called
nucleotides
○ 5-carbon sugar,
deoxyribose
○ Phosphate group
○ Nitrogen base
(A,T,C,G)
Nitrogen Bases
What are the 3
components to a
nucleotide?
Purines
Pyrimidines
- Adenine (A)
- Guanine (G)
- Structure has
TWO rings
- Cytosine (C)
- Thymine (T)
- Structure has
ONE ring
A pairs with T
G pairs with C
Held together by
hydrogen bonds
Base Pair Rule (Chargaff’s Rule)
Our genetic alphabet
One side: A T A
T C A
T G C
G G G
A G T
A C G
C C C
Think of the bases of
DNA like letters.
Letters form words …
Other Side:
T A T
Words form sentences …
Moving the “letters” of
DNA around forms
different “words”
- CATCAT = purple hair
- TACTAC = yellow hair
Base Pair Rule
What is the shape
of DNA?
Adenine pairs
with_______.
The sides of the
DNA ladder are
deoxyribose and
_________.
DNA Replication
12-2 DNA Replication
In what phase of
the Cell Cycle
was DNA copied?
● Process of copying DNA
● Occurs in the nucleus before a cell divides
● 2 steps
○ Step 1: DNA molecule is “unzipped”
■ Hydrogen bonds between bases are broken
○ Step 2: New strands are made using the original strands by
complementary base pairing
■ DNA polymerase - enzyme that pairs the nucleotides
together
● Semi-conservative -- half of the old strand is saved
Animation
DNA Replication
Let’s Practice!
RNA
● Single stranded
12-3 RNA Structure
and Types
○ Ribose sugar
○ NO thymine,
uracil (U)
instead
○ A pairs with U
DNA: A T A G C G
RNA: U A U C G C
RNA
DNA
Ribose
Deoxyribose
Yes
Yes
Bases
AUGC
ATGC
1. mRNA (Messenger RNA) carries copies of instructions to
assemble amino acids
Length
Short
Long
2. rRNA (Ribosomal RNA) makes up ribosomes
Strands
Single
Double
Sugar
Phosphate
3 types of
RNA
So, what is the relationship between genes and DNA? A section of DNA that codes
for a protein and results in a trait.
3. tRNA (Transfer RNA) Transfer amino acids to ribosomes to
be put together as proteins
Name 3
differences
between RNA
and DNA.
12-3 Transcription and
Translation
The Central Dogma -- From DNA to Protein
What is a protein?
● Building blocks
of organisms
(traits)
● Another
macromolecule
● Polymer (long
chain) of
amino acid
Transcription
● RNA is made from DNA
● Step 1: RNA polymerase
binds to DNA and
“unzips” the strands
● Step 2: One strand of
DNA is used as template
to create mRNA strand
● Step 3: RNA is released
● Occurs in the nucleus
How do you use this diagram?
CGU
1. Start in the middle
2. Move outward,
finding the next base
in the codon.
Arginine
What other codons code for Arginine?
Before mRNA can
move on…
It must be edited
Introns- non-coding
sequences of mRNA
Genetic Code
mRNA
Exons- sequences that
contain the code for a
protein
Introns are removed by
the Spliceosome
Anticodons
● Located on the
tRNA
● 3 base segments
that correspond
with the codon
in the mRNA
Read 3 letters a time= codon
There are 20 amino acids
(building blocks of proteins)
Stop codons do not code for
anything and end the sequence
Start codon-AUG-Methionine
Translation
Process where
proteins are made
from RNA
Occurs in the
cytoplasm
Translation Steps
Step 1: Ribosome binds to mRNA
Step 2: Ribosome matches tRNA anticodon to the mRNA codon
sequence
Step 3: New tRNA enters ribosome, the attached AA gets added to
the polypeptide chain
Step 4: Ribosome continues until stop codon, then it releases the
chain and the mRNA
What two things
are attached to
the tRNA?
What is the start
codon?
What occurs in
Transcription?
The fat man sat on the cat.
1. The atm ans ato nth eca
2. TThefatmansa ton the cat
What is a mutation?
1.
2.
3.
Deletion
Insertion
Duplication
3. The fat mma nsa ton the cat
12-4 Mutations
Discussion Questions:
#1. Identify the change in the letter sequence that has been made in each of the altered phrase examples.
#2. Do any of the altered phrases have the same meaning as the original phrase?
#3. How many letters were changed (added, deleted, or duplicated) in each of the phrases?
#4. How does this practice problem relate to DNA and our study of genetics?
Gene Mutations
Point Mutations
Occur at a single point in
DNA
● Substitution - one base is
changed to another
○ Usually affect no
more than one amino
acid
●
Frameshift mutations
● Occur at a single point in
DNA
● Insertion - one base is
added
● Deletion - one base is
removed
● Usually affect MANY
amino acids
Gene Mutations
Frameshift mutations
Point Mutations
Example of Insertıon:
THE FAT CAT ATE THE RAT
THE FAA TCA TAT ETH ERA
Example of Substıtutıon:
THE FAT CAT ATE THE RAT
THE FAZ CAT ATE THE RAT
Example of Deletıon:
THE FAT CAT ATE THE RAT
THE ATC ATA TET HER AT
Change in DNA
sequences
Can happen in the
gene or the whole
chromosome
Chromosomal Mutations
Duplication
Remember chromosome structure…
● Change in the number of or
structure of a chromosome
● Could change the locations
or number of genes
● 4 types:
○ Duplication
○ Deletion
○ Inversion
○ Translocation
Deletion
Inversion
Translocation
● A part of the
chromosome
is removed
● Reverse the
direction of
parts of
chromosomes
● Part of one
chromosome
breaks off and
joins another
BEFORE
AFTER
● Produce extra
copies of parts
of chromosomes
● Segment is
repeated
BEFORE
AFTER
What do mutations do?
● Most have no effect
● They are the source of genetic variability
● Helpful mutations
○ Plants with extra sets of chromosomes are often larger and
stronger
■ Ex: Bananas
● Harmful mutations
○ Many different disorders like cystic fibrosis and sickle cell
○ What is one that we talked about last unit?