Download presentation
Presentation is loading. Please wait.
1
Protein Synthesis
2
Where is DNA found. What organelle makes proteins
Where is DNA found? What organelle makes proteins? Where are these organelles found? How does the information from DNA get to those organelles?
3
Protein Synthesis Overview
The information in DNA is used to make proteins. These proteins are used for a variety of purposes within the body. (do you remember why our body needs protein?)
4
However there is a problem. The DNA never leaves the nucleus
However there is a problem. The DNA never leaves the nucleus. But the ribosomes, (remember? they make proteins) are in the cytoplasm. How can the information get from the nucleus to the ribosomes in the cytoplasm? The solution is that the cell makes a temporary copy of the DNA. The temporary copy is called RNA.
5
RNA RNA stands for ribonucleic acid
Found in both the nucleus and cytoplasm Role: create a temporary copy of the instructions in DNA to send to the ribosome
6
RNA Structure Single stranded Like DNA, RNA is made of nucleotides
RNA nucleotides consist of: 1. Phosphate (acid) 2. Ribose (sugar) 3. Nitrogenous base
7
Nitrogen Bases 1. Adenine (A) 2. Uracil (U) – replaces thymine
3. Cytosine (C) 4. Guanine (G)
8
3 Types of RNA 1. mRNA rRNA tRNA
9
Messenger RNA (mRNA) Acts as a messenger, carries a copy of the directions from the DNA in the nucleus to the ribosome in the cytoplasm
10
2. Ribosomal RNA (rRNA) Part of the ribosome The ribosome is made up of proteins plus rRNA.
11
3. Transfer RNA (tRNA) Remember:
Ribosomes make proteins, which are made of amino acids tRNA brings those amino acids to the ribosome to be assembled into the correct order Anti-codon
13
Draw DNA & RNA with their 4 bases in your notebook.
14
DNA and RNA Similarities Differences Differences
15
The Central Dogma of Biology
16
2 Steps: 1. Transcription 2. Translation Protein Synthesis
Stated Clearly Video 2 Steps: 1. Transcription 2. Translation
18
Step 1: Transcription Transcription is the first step in protein synthesis. Purpose: to make RNA, a copy of the information in DNA. Location: in the nucleus. To get started you need: DNA Free RNA nucleotides RNA polymerase
20
Step 1: Initiation RNA polymerase attaches to a promoter region of DNA Promoter= specific sequence of DNA
21
Step 2: Elongation RNA polymerase opens the DNA helix. It makes a little bubble. One strand will act as a template. RNA polymerase moves down the DNA molecule attaching complementary RNA nucleotides as it goes.
22
Step 2: Elongation Everything is the same as DNA replication except: The DNA A pairs with RNA U
23
Match the DNA bases to the RNA bases
G C RNA
24
Step 3: Termination Transcription stops when RNA polymerase reaches the terminator region of DNA. Terminator signals end of the gene.
25
RNA polymerase then detaches from the DNA
Step 3: Termination RNA polymerase then detaches from the DNA mRNA sent out of nucleus to cytoplasm after mRNA editing Stated Clearly Video Transcription Video Animation
26
Summarize Transcription in your notebooks (bullet points)
Check your summary with a partner when finished.
28
mRNA Editing Occurs directly after Transcription Aka RNA splicing- essentially cutting and pasting of the mRNA DNA & RNA contain portions called introns and exons
29
mRNA Editing EXONS: pieces of DNA that are expressed- used to make proteins these are kept in mRNA INTRONS: Not used to make proteins: Removed from mRNA
30
mRNA Editing Finally: A cap and a tail are added to the ends of the mRNA Purpose: Facilitates export out of nucleus Protects from attack by enzymes Helps ribosomes bind to it
31
Answer these questions in your notebook:
What are introns and exons? Introns are pieces of DNA that do not code for proteins. Exons code for proteins Are introns or exons important for protein synthesis? Exons are necessary for protein synthesis- exons give us instructions to make proteins Why do we edit the mRNA after copying DNA? We edit out the introns because we only want the parts of the DNA that tell us how to make proteins. For protein synthesis, the introns are useless.
33
Step 2: Translation Location: In ribosomes in the cytoplasm
Purpose: To make proteins How It Works: The mRNA (copy of the DNA info) created in the nucleus moves to the ribosome in the cytoplasm Ribosome reads the mRNA which tells the ribosome which amino acids to put together to make a protein
34
How do we read mRNA?: mRNA contains codons- every 3 bases on mRNA = 1 codon These codons code for (give instructions for) a certain amino acid There are multiple codons for 1 amino acid tRNA reads these codons and carries the necessary amino acid to the ribosome
35
Translation- Step 1. Initiation
2 ribosomal subunits attach to the mRNA There is a START codon on mRNA which tells the ribosome to start bringing amino acids to it.
36
Translation Mechanism
MET This process continues until a stop codon is reached, at which point the mRNA strand, tRNA units, and rRNA subunits all are released. MET ISO PRO A U G C tRNA U A U tRNA U A C tRNA U A C tRNA U A U tRNA G G G Start Codon (Methionine) Large Ribosomal Subunit (rRNA) E Site A Site P Site mRNA A U G C Small Ribosomal Subunit (rRNA)
37
Step 2: Elongation mRNA= has codon
A. Codon recognition occurs mRNA= has codon tRNa = has anti-codon which matches the mRNA codon tRNA with anti-codon that matches the mRNA START codon attaches to ribosome, bringing an amino acid with it Another tRNA attaches to ribosome
38
Step 2: Elongation B. Peptide Bond Formation
Ribosome forms a peptide bond between the amino acids from tRNA to start a chain Old tRNA leaves ribosome while new one attaches- continues until STOP codon reached
41
Step 3: Termination STOP codon is reached
STOP codon tells tRNA to stop binding to ribosome Ribosome pulls away from mRNA Translation complete- ending with a complete protein Translation Animation
42
Post-Translation . . . The new protein is released. The string of amino acids fold- up into the shape of the protein. Protein sent to Golgi for packaging and shipping
43
Summarize Translation in your notebooks (bullet points)
Check your summary with a partner when finished.
48
Practice Creating Proteins
Using the chart on your guide, find the amino acid sequence created from the following strands of DNA:
49
Genetic Mutations Mutation = Changes in the DNA sequence
Mutagenesis – the production of mutations Mutagen – something that causes mutations A physical or chemical agent such as x-rays, high-energy radiation, chemicals Spontaneous – occur during replication or other similar processes Genetic mutations
50
Gene Mutation
51
Two types of Mutations Point mutation (results from substitutions)
Gene mutations – within a single gene Point mutation (results from substitutions) Ex: TAC changes to AAC Genetic disorder ex: Sickle cell anemia, Cystic Fibrosis Silent mutation – diff codon, but same amino acid Frameshift mutation (results from insertions/deletions) Ex: insert a T after first T so TAC – GCC changes to TTA – CGC - C
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.