Download DNA, RNA, Protein Synthesis - Social Circle City Schools

DNA, RNA, and
Protein Synthesis
What is DNA?
• DNA- Deoxyribonucleic Acid
• Function is to store and transmit hereditary
information.
• In prokaryotes- located in the cytoplasm
• In eukaryotes- located in the nucleus
Structure of DNA
• DNA is a DOUBLE HELIX- 2 strands wound
around each other like a twisted ladder.
• Strands are held together by weak hydrogen
bonds.
• The building blocks of DNA are called
NUCLEOTIDES (made up of 3 things):
– Sugar (deoxyribose)
– Phosphate
– Nitrogen base
Make up the backbone
or sides of the DNA
ladder
Four Nitrogen Bases
•
•
•
•
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Chargaff’s Rules
• A and T always bond together
• C and G always bond together
Coloring sheet
• coloring sheet.docx
DNA History
• Frederick Griffith (1928): discovered the molecular
nature of genes while studying how bacteria make
people sick.
History continued
• Oswald Avery (1944): discovered that
DNA is the nucleic acid that stores and
transmits the genetic information from one
generation to the next.
History continued
• Hershey and Chase Experiment (1952):
concluded that the genetic material of
bacteriophage (virus that infects a
bacteria) is DNA and not protein.
History continued
• Rosalind Franklin (1952): used x-ray
diffraction to show that DNA strands are
twisted into a helix shape.
History continued
• Watson and Crick (1953): credited with
the discovery of DNA as a double helix.
Wanna see something…
• cheek cell- studentcopy.docx
DNA Replication- copying the DNA
for Cell Division
• In order for a cell to divide it must make a
copy of its chromosomes- the DNA is
inside the chromosomes.
Process of DNA Replication
• Enzymes (RNA polymerase) “unzips” molecule
of DNA at the hydrogen bonds between the
nitrogen bases.
• Nitrogen bases that are floating around in the
nucleus base pair with the unzipped DNA to
make 2 new strands:
– Each new strand contains an original strand and a
new strand of DNA.
• Example –
TACGTT original strand
ATGCAA compliment strand
Watch This!!
• Replication
• We do this for Mitosis!! We can also use
this in Meiosis to copy the information to
be passed on!
Steps of Replication
• 1. Unwinding of DNA using the enzyme
Helicase which unwinds and unzips the H
bonds while proteins attach to the strand
to keep it unzipped.
• RNA primase (another enzyme) adds
short RNA segments to the DNA strand
Step 1
Step 2
• Base pairing- enzyme DNA polymerase
catalyzes the addition of appropriate
nucleotides following Chargaff’s rules
•
A–T
•
C–G
• Okazaki Fragments attach short portions
at a time
Step 2
Step 3
• Joining- DNA polymerase reaches the
RNA primer and removes the primer and
fills in DNA nucleotides and DNA ligase
links the sections
Step 3
PRO VS EU
TADA!!!
• You have a copy of your DNA!!!!
So then what?
• Your cell has to function and go through
daily living called its metabolism.
• To do that we have to make
• PROTEINS!!!!!!
Proteins
HOW? RNA- ribonucleic Acid
• Function of RNA is protein synthesis- to
make proteins.
• Made up of nucleotides
– Sugar (ribose), phosphate and a nitrogen
base
• Single stranded instead of double
stranded
• Contains uracil instead of thymine
• Located in the cytoplasm not the nucleus.
3 types of RNA
3 Types of RNA
• Messenger RNA (mRNA): goes into the
nucleus and reads DNA “code” then
carries it to ribosome.
• Ribosomal RNA (rRNA): makes up the
ribosome where proteins are made.
• Transfer RNA (tRNA): transfers each
amino acid to the ribosome as coded by
mRNA (from DNA).
Protein Synthesis
• Making proteins using the DNA code.
• Proteins are enzymes that regulate all
chemical processes of living
organisms.
• Proteins are made on RIBOSOMES!
• Made by joining amino acids into long
chains called polypeptides.
• There are 20 different amino acids.
Amino Acids
Codons and Amino Acids
• Codon - genetic code for an amino acid
that is 3 letters (nitrogen bases) long.
– Example: UCGCACGGU
UCG CAC GGU
• These codons represent the amino acids.
• There are stop and start codons.
• AUG means “start.”
• UAA, UAG, UGA are “stop” codons
Steps of Protein Synthesis
Step 1- TRANSCRIPTION: decoding DNA into
RNA
a. Enzyme called RNA polymerase separates
DNA into a single strand (serves as the
template for mRNA).
b. mRNA goes into the nucleus to decode the
DNA (uracil subs for thymine).
c. mRNA carries the sequence to the
ribosome.
Transcription
Step 2 - Translation
Step 2- TRANSLATION: decoding mRNA to
make a protein
a. tRNA is called the anti-codon. It attaches
to the mRNA to pick up the amino acids
and carry them to the ribosome.
b. The mRNA sequence is used as the code to
find amino acids.
c. Amino Acids combine until a STOP codon is
reached. A protein is made!
Translation
video
• Cartoon
• 3D
• sentence decoding lab.doc
Mutations
• Mutations – Change in DNA sequence that
affects genetic information.
Gene Mutations
• Point Mutations: mutations that affect only one
nucleotide. One nucleotide is substituted for
another.
• Frameshift Mutation: deleting a nucleotide or
inserting a new nucleotide. This shifts the
reading of the Genetic code.
Chromosomal Mutations
• Chromosomal Mutations – changes in the
number or structure of chromosome.
– Deletion- loss of part of chromosome.
• Ex: ABC-DEF changes to AC-DEF
– Duplication- sequence of chromosome is
repeated.
• Ex: ABC-DEF changes to ABBC-DEF
– Inversion – reverse of usual direction
– Translocation – one part breaks off and
attaches to another.