DNA, RNA and PROTEIN SYNTHESIS sections 12.3 and 12.4
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Transcript of DNA, RNA and PROTEIN SYNTHESIS sections 12.3 and 12.4
DNA, RNA and
PROTEIN SYNTHESIS
sections 12.3 and 12.4
What is protein synthesis?
What is the relationship between
DNA and RNA
and protein synthesis?
What functions do proteins
perform in living things?
Ribonucleic Acid (RNA)…
• organic compound (contains C+H)• polymer - composed of monomers called nucleotides• composed of a SINGLE STRAND of nucleotides • carries out protein synthesis (the making of proteins)
3 types of RNA…. messenger RNA (mRNA) transfer RNA (tRNA) ribosomal RNA (rRNA)
Ribonucleic Acid (RNA)
RNA takes on 3 different shapes.
All are used in protein synthesis.
Transfer RNAMessenger RNA
Ribosomal RNA
RNA nucleotide has 3 parts…
1. a ribose sugar covalently2. a phosphate group bonded3. a nitrogen base
of which there are 4 kinds - A, U (uracil), C,G
In RNA – uracil takes the place of thymine
In RNA…. A pairs with U C pairs with G
RNA nucleotide structure:
Phosphate GroupNitrogen Base (A, U, C, G)
Ribose Sugar
RNA nucleotide structure:
PHOSPHATE GROUP
RIBOSE SUGAR
NITROGEN BASE
(A, U, C, G)
RNA differs from DNA:
RNA has… 1. ribose sugar
(instead of deoxyribose) 2. a single strand of nucleotides
(instead of a double helix) 3. the N base uracil
(instead of thymine)
Transcription…the process of making RNA from DNA
template2 steps:
1. an enzyme separates N-bases of DNA
2. a complementary RNA chain is made
the RNA breaks away and
the DNA reforms
3 products: mRNA, tRNA, rRNA
Messenger RNA (mRNA)
• linear form
• carries the message from nucleus to a ribosome (site of protein synthesis)
mRNA
3 N bases = codon
each codon codes for a specific amino acid
Transfer RNA (tRNA)
• “t” shaped
• transfers amino acids to the site of protein synthesis (ribosome)
tRNA
3 N bases = anticodon
anti-codons align with codons on mRNA
Ribosomal RNA (rRNA)
• globular form
• makes up ribosomes
• this is where protein synthesis occurs
rRNA
Importance of Protein…
Your body uses the proteins you eat (the amino acids you ingest)
to make specialized proteins
that have specific jobs!!!
LIKE…. Insulin, Actin, Hemoglobin, Collagen and Elastin, Pepsin and Trypsin and other enzymes, Antibodies and many, many more…..
You need protein !!!!
PROTEIN TYPES FUNCTIONS EXAMPLE
enzymes catalyze specific reactions TRYPSIN PEPSIN
S structural proteins
strengthen cells COLLAGEN
storage proteins store nutrients ALBUMIN in egg white
transport proteins transport substances HEMOGLOBIN transports oxygen RBC’s
regulatory proteins control cell actions INSULIN hormone important in regulation
of blood sugar
motile proteins involved in cell movement ACTINprotein in muscle cells important
in contraction
protective proteins defend cells ANTIBODIES produced by some types of WBC’s
Proteins are the MOST VERSATILE cellular components
Translation….the making of proteins from the information encoded in DNA
this process makes ALL types of proteins
amino acids polypeptide chain proteinoccurs at a ribosome (site of protein synthesis)
In this process all 3 types of RNA are used . . . . . mRNA carries the instructions for making a protein tRNA transfers amino acids (materials) to the ribosome rRNA assists in the binding of mRNA and tRNA
Steps in Translation
1. mRNA leaves nucleus and goes to ribosome
2. tRNA carries amino acids to ribosome
3. codons (on mRNA) + anticodons (on tRNA) align and bring amino acids into their correct sequence
4. When100 amino acids are assembled = polypeptide chain
5. polypeptide chains will detach and wrap with other chains to form a protein
* process only begins with a start (AUG) codon
* process will only stop with a stop codon (UGA, UAG,…)
A look at translation…
Let’s look at it again
RNA Editing –
RNA molecules require a bit of editing before they are ready to go into action
Introns – a non-coding sequence of RNA
(does not code for a protein)
“a deleted sequence of RNA”
Exons – an expressed sequence of RNA
Introns – Deleted sequence of RNA Exons – Expressed sequence of RNA
The Genetic Codeamino acids polypeptide chains proteins
the genetic code is read 3 letters at a time
example - AUG, CAA, UCG, ACC, GAC
each sequence of 3 letters “codes” for
a specific amino acid
as amino acids are put into a specific order
they produce a specific type of protein
MUTATION = a change in the DNA (nucleotide) sequence
mutations may be helpful, harmful or have no affect at all mutagens – substances which cause mutations body cell mutation versus sex cell mutation
Mutations are of 2 kinds:• GENE MUTATIONS• CHROMOSOME MUTATIONS
GENE MUTATIONS• a mutation in a single gene• it may involve 1 or several nucleotides
GENE = REGION/SEGMENT OF DNA THAT CODES FOR A PARTICULAR TRAIT
POINT MUTATIONS
mutations that affect 1 nucleotide
substitution, insertion (addition) or deletion
original sequence ACC,UUA,GAC…
substitution ACG, UUA, GAC…
insertion ACC, CUU, AGA, C…
deletion _CCU, UAG, AC…
FRAMESHIFT MUTATIONS
a point mutation caused by the INSERTION or DELETION of a single nucleotide
results in a shift of the “frame of reference” in the reading of the N base sequence
original sequence ACC,UUA,GAC…
insertion ACC, CUU, AGA, C…
deletion _CCU, UAG, AC…
CHROMOSOME MUTATIONS
– involve segments or whole chromosomes
types of chromosome mutations include: deletion, inversion, translocation, nondisjunction
we have already studied these
Gene Regulation the ability to control (regulate) which genes are
transcribed (“turned on”) different genes may be transcribed (“turned on”) at
different times during an organism’s life a gene is expressed or “turned on” only if
transcription occurs
OPERON – segment of DNA that contains the genes for the proteins to be transcribed
OPERATOR – segment of DNA that acts as an on/off switch for transcription
Special Genes
Hox Genes (or homeobox genes) genes that determine the basic body plan of an
organism control what body part will develop in a given
location control DIFFERENTIATION - process through which
the cells become specialized in structure and function
a mutation in one of these genes can completely change the organs that develop in specific parts of the body
Special GenesOncogenes – genes that promote uncontrolled cell division which may
lead to cancer – genetic mutations may result to the activation of oncogenes
Tumor Suppressor Genes – genes that act to prevent DNA damage and inhibit uncontrolled cell division which may prohibit cancer development
ONCOGENES AND TUMOR SUPPRESSOR GENES ARE THOUGHT
TO BE IN A PERPETUAL TUG-OF WAR
Remember, a gene is not “turned on” until it goes through transcription
To summarize:
1. TranscriptionDNA RNA
2. TranslationRNA Protein