Download DNA notes 2015 - OG

DNA COMPETITION
Come up with a team name that’s DNA-related
Team with the most points gets a special prize!
G
DNA – Deoxyribonucleic Acid
DNA is made up of repeating…
Nucleotides – has 3 components:
1. Phosphate Group
2. Sugar – Deoxyribose
3. Nitrogen Base (4 of them)
C
A
T
C
G
T
A
Thymine always bonds with Adenine
Guanine always bonds with Cytosine
**The part that carries the code is the base sequence
Covalent bond – connects nucleotides in a strand
G
C
G
C
Hydrogen bonds – they connect the 2 strands
together
Forms shape of DNA – DOUBLE HELIX
• Chargaff’s Rule:
[A]=[T] and [C]=[G]
• X-Ray diffraction
pictures helped
solve the structure of
DNA’s double helix
• Finalized the
structure of DNA
and built the first
ever DNA model
DNA is shaped like a double helix (a twisted ladder)
This shape was discovered by two scientists: James
Watson & Francis Crick (Impossible without Rosalind
Franklin’s X-Ray diffraction photo of DNA!)
In general, DNA is replicated by
1. Uncoiling of the helix
2. Separating the strands (breaking the
hydrogen bonds between base pairs)
3. Synthesizing two new strands by
complementary base pairing
DNA replication begins at 1
point, called the “origin” and
proceeds in 2 directions
(bidirectional)
Hydrogen bonds break, two
strands separate, 2 new
strands are added to the
old strands (SEMI
CONSERVATIVE)
DNA Replication –
- DNA makes a copy of
itself
- Important during meiosis
& mitosis – DNA gets
passed on to daughter
cells
• DNA polymerase adds nucleotides to the parent
strands and checks the strand for errors
• Each double helix now has 1 old strand & 1 new
strand
•This is called SEMI-CONSERVATIVE
• If the original strand of DNA is ATTGCACT, what is
the complementary strand…?
• The tips of chromosomes
are called telomeres
• Genes are not found in this
region of the chromosome
•These areas are difficult to
replicate, so an enzyme –
telomerase – adds short,
repeated sequences to the
ends
1. Label ONE strand of your DNA with any
sequence of your choosing
2. Label the opposite strand, following the
base-pair rules
3. What’s the 1st step in DNA replication
- The DNA “unzips” – crease your paper and
“unzip” your DNA
4. What’s the 2nd step in DNA replication?
- DNA Polymerase adds nucleotides
- Lay your strands about 2” apart on a
piece of paper
- Next to each original strand, write the
NEW complementary DNA sequence
- You should now have 2 identical doublestranded molecules of DNA…yes?
DNA holds the directions for protein synthesis
Protein synthesis is the making of proteins
A gene is a sequence of DNA that carries the
code for making one protein
Protein Examples
Hemoglobin is a protein in your blood
that transports oxygen
Collagen is a proteins that makes your
cartilage and tendons
Keratin is a protein that makes
up your hair & fingernails
Enzymes that break down your food are proteins
Everything in you is made of or
by proteins!
RNA is like DNA except…
DNA – Deoxyribonucleic
acid
RNA – Ribonucleic Acid
* 2 strands vs. 1 strand
Nitrogen
Bases
* Thymine vs. Uracil
(others are the same)
Sugars
&
Phosphates
* Deoxyribose vs. Ribose
* Nucleus vs. Cytoplasm
RNA
DNA
Types of RNA
1. mRNA – “messenger” RNA
- Carries copies of instructions from DNA for
making amino acids into proteins
2. tRNA – “transfer” RNA
- Transfers each amino acid to the ribosome as
specified by the code on mRNA
3. rRNA – “ribosomal” RNA
- Makes up part of the ribosome, where
proteins are made
•
Both DNA and RNA are involved in
protein synthesis
2 parts of protein synthesis:
1. Transcription – DNA is converted to RNA
-
Occurs in the nucleus
2. Translation – RNA is converted to a
protein
-
Occurs in the cytoplasm
• Transcription (the 1st part of
Protein Synthesis)
• Converts DNA to RNA
• DNA (in the nucleus) needs to
send a code to the ribosome (in
the cytoplasm)
• Problem: DNA can’t fit through
the nuclear pores
• A special “messenger” is
used to copy and carry the
code…
Transcription Cont’d
• messenger RNA (mRNA) goes
into the nucleus and copies the DNA
• Uses enzyme – RNA Polymerase
• The next step is that mRNA moves
from the nucleus to the cytoplasm
and to the ribosome
• RNA has 1 different base pair!
DNA – ATCG
mRNA – UAGC
nd
(2
Translation
part of protein
synthesis)
• Amino acids – building blocks of proteins,
carried to ribosomes by ______________
tRNA
Amino Acids
• Polypeptides – long chains of ____________
3 nucleotide bases in mRNA which
• Codon – group of ____
carries code for making _______________________
ONE amino acid
• Ex:
AUG - Methionine
3
• Anticodon – group of _____
nucleotide bases in tRNA
codon
which is complementary to one ___________________
Translation Cont’d
• mRNA
____________ attaches to the ribosome
• tRNA
____________ carries amino acids to the
ribosome and matches them to the coded
mRNA message (codon)
• Amino acids bond together, forming a long
Polypeptide chain
chain called a ____________________
• Finally, polypeptides fold into various
types of proteins and there you have it!
Translation (the 2nd part of Protein Synthesis)
• Translation – a process that converts mRNA into a protein
• Occurs on the ribosome in the cytoplasm of a cell
• ______________
- building blocks of proteins; join together
Amino acids
into long chains called polypeptides
Codon
• ____________
- a sequence of 3 bases on mRNA that codes
for a single amino acid
Anticodon
• _____________
– sequence of 3 bases on tRNA that is
complementary to one mRNA codon
“UCU” is the
codon that makes
an amino acid
called SERINE
• Another form of RNA called
transfer RNA (tRNA) carries
amino acids to the ribosome
and matches them to the
coded mRNA message
•The tRNA lines up with 3
bases in mRNA (codon)
•tRNA anticodon GAA
•mRNA codon CUU
•tRNA drops off the amino acid in the correct spot
mRNA attaches to the ribosome
Any change in the DNA structure (specifically the order
of nitrogen bases) is a mutation.
Mutations can be helpful, harmful, or neutral.
Helpful – can create diversity in a population
Harmful – can cause things like cancer
Neutral – can have absolutely no effect
at all
A mutagen is something that causes
mutations in the DNA (for example:
smoking, radiation from the sun etc)
Slooze Worm
An insertion mutation is when a nitrogen base is added to the existing DNA
A deletion mutation is when a nitrogen base is subtracted from the DNA
A substitution mutation is when one nitrogen base is put in place of another.
If our DNA was AATTGGCC
An insertion would be AATTAGGCC
A deletion would be AATGGCC
A substitution would be AAATGGCC
Gene Sequencing – Determining the order of nucleotide bases within a gene
DNA Fingerprinting – technique used in criminal investigations. DNA
Fingerprinting takes the DNA out of a cell and separates it. This will allow
investigators to distinguish body cells of different individuals (since they
are unlikely to have the same DNA)
Cloning – take the DNA out of one of your cells then take the DNA out of a
zygote (fertilized egg). Put the DNA from your cell into the zygote.
Genetic engineering is the
process of moving genes
from the chromosomes of
one organism to those of
another organism.
Recombinant DNA is
formed by joining DNA
molecules.from two
different organisms
What would represent the strand of DNA from which the mRNA strand in the
diagram was made?
A.CUCAAGUGCUUCB.GAGUUCACGAAG
C.GAGTTCACGAAGD.AGACCTGTAGGA
What is the amino acid sequence in the portion of the protein molecule coded
for by the piece of mRNA shown in the diagram?
A. Ser-Tyr-Arg-GlyB.Leu-Lys-Cys-PheC.Val-Asp-Pro-HisD.Pro-GluLeu-Val