Download What is DNA?

DNA – The molecule of Heredity
Chromosome - Carrier of genetic material,
a long strand of coiled DNA
Gene – a segment of DNA found
on a chromosome
1 gene =
code to make 1 polypeptide (protein)
What is DNA?
A molecule, Deoxyribonucleic Acid,
that holds the master copy of an
organism’s genetic code.
DNA – The molecule of Heredity
What is DNA? Deoxyribonucleic Acid,
Click here for video onDNA
Why is DNA important?
Knowledge of DNA is critical for
understanding…
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Birth Defects
Cancer
Genetic Engineering
Viral Diseases
Aging
Criminal Investigation
Who Discovered the structure of
DNA? Watson and Crick – 1953,
discovered that DNA was
made of two spiral
strands, they called it a
double helix.
DNA – The molecule of Heredity
What are the building blocks of DNA?
- Subunits called Nucleotides make up DNA.
Nucleotides are made up of:
1. A simple sugar – deoxyribose
2. A phosphate group
3. A nitrogen base (one of four)
a. Adenine (A)
b. Thymine (T)
c. Cytosine (C)
d. Guanine (G)
A Closer Look at DNA Untwisted
The 2 strands are held together by a weak hydrogen bond.
The 2 strands are held together at the nitrogen bases.
Adenine will bond with Thymine
Cytosine will bond with Guanine
Hydrogen Bond
These are called complimentary
base pairs
Deoxyribose
Sugar
Phosphate
Group
Covalent
Bond
Covalent
Bond
DNA Replication
What process have we already discussed that involves DNA Replication?
The Cell Cycle!!!!!!!!!! (more specifically, interphase!)
Remember… DNA
needs to replicate so
that when the cell
divides in half, the
two daughter cells
will have the same
genetic information!
DNA Replication
1.DNA untwists
DNA Replication
2. Two chains unzip or separate
DNA Replication
3. Free floating
nucleotides in the
nucleus bonds to the
unzipped strands by
base pairing with the
help of enzymes.
DNA Replication
4. Two identical DNA
molecules are formed.
DNA Replication - RECAP
Process:
1. DNA untwists
2. DNA unzips and separates
3. Free floating DNA nucleotides in the nucleus come
and bond to the unpaired strands of DNA.
4. 2 identical DNA molecules are formed
Product:
- 2 DNA molecules that are exactly alike.
**Replication is Semi-Conservative – meaning that the 2 old DNA
halves are used as patterns on which to build to new halves.
DNA Replication Active
Art
Active Art Clip of
DNA Replication
What is RNA?
RNA strands for Ribonucleic Acid
Differences in RNA and DNA:
DNA
RNA
Double or Single
Stranded
Double
Single
Nitrogen Bases
Thymine
Uracil
Sugar
Deoxyribose
Ribose
RNA is used in the processes of transcription and translation.
There are 3 different types of RNA.
RNA
Function
mRNA – messenger
RNA
A copy of DNA. Takes information
from the nucleus to the ribosome.
tRNA – transfer RNA
Transports amino acids to the
ribosome to be assembled into a
protein
rRNA – ribosomal RNA
Makes up the ribosome; assembles
proteins
We know that DNA is very important because
it gives our bodies instructions to make
proteins. But how does it do that???
To go from
DNA  proteins,
DNA must first
become RNA
and then go
through several
processes to
become a
protein.
How does DNA turn into RNA and then make a
protein?????
This happens through a
process called protein
synthesis.
Protein synthesis is made up
of 2 main parts:
1. Transcription
2. Translation
Let’s look at what we know
about proteins so far…
1. Proteins are made up of amino
acids.
2. Proteins are in our foods, such as
meats.
3. Enzymes are a type of protein.
4. Antibodies are a type of protein.
Considering all of that, we have already
learned that proteins are pretty important.
Therefore, our DNA must be pretty
important too!
Transcription
- Transcription: Making a copy of mRNA from DNA
- mRNA (messenger RNA) = A copy of DNA. Takes
information from the nucleus to the ribosome.
- Transcription takes place in the nucleus of the cell!
Practice:
DNA
TAC CGA GTA ACT
mRNA
AUG GCU CAU UGA
Transcription
1.DNA untwists
Transcription
2. Two chains unzip or separate
Transcription
3. Free RNA nucleotides
pair with
complementary DNA
nucleotides on one of
the DNA strands.
Transcription
4. mRNA breaks away as
the DNA strands rejoin
Transcription - RECAP
Process:
1. DNA untwists
2. DNA unzips and separates
3. Free floating RNA nucleotides in the nucleus come
and pair with their complementary DNA pair.
4. The mRNA breaks away and the DNA comes back
together.
Product:
- 1 single-stranded mRNA molecule
- The same double-stranded DNA molecule
that you started with.
Transcription video
Translation
- Translation: converting the mRNA message into a sequence of
amino acids to form a protein
- tRNA (transfer RNA) = brings the amino acid to the ribosome
- Each tRNA carries only 1 amino acid!
- Translation takes place at the ribosomes in the cell!
- Codon = 3 nitrogen bases on DNA or mRNA. Each codon
represents 1 of 20 amino acids.
• START CODON – AUG codes for the amino acid Methionine
and starts protein synthesis
- Anticodon = 3 bases on tRNA that bond to the codon of mRNA
Translation
1.mRNA attaches
to the ribosome
Translation
2. tRNA anticodon pairs with
mRNA
Translation
3. Amino Acids are
joined together with
peptide bonds to
make a protein.
Translation – RECAP
Process:
1. mRNA attaches to the ribosome
2. tRNA anticodons pair with mRNA
3. Amino Acids are joined together with peptide bonds to
make a protein.
Product:
- Protein!!!!!!!!!!
(determined using a codon chart)
Video on translation
How can I tell which codons are used to make the
protein? Codon Chart
Protein Synthesis – RECAP
Replication and Protein Synthesis
Web Activity
http://www.pbs.org/wgbh/aso/tryit/dna/
Just like everything else in our bodies, there is a
chance that this process will mess up.
When replication, transcription or translation
mess up, we call it a mutation.
If the order of bases change
Genes will change
Trait will be expressed differently
Mutations
Mutation – any mistake or change in the DNA Sequence, both random or from radiation/chemical
exposure (only changes in the gametes will be passed on from parent to offspring)
Types of Mutations:
1. GENE MUTATION
If the order of bases changes
Amino Acid Sequence changes
Proteins function changes
Changes Phenotype
a. Substitution or Point Mutation – change in a single base pair
b. Frameshift Mutation – addition or deletion of a single base pair