What is the function of DNA Making proteins

What is the function of DNA?

• Making proteins • When genes are expressed, proteins are synthesized • It involves two stages – transcription and translation

Learning Outcomes • Explain the processes involved in transcription • The different nucleic acid needed and its structure • Explain the difference between primary and mature transcript

DNA recap. . answer these. . . 1. 2. 3. 4. 5. 6. An examples of? MY LOPER Made up of? Different types of bases? Number of strands? Held by? What is the triplicate code?

DNA and RNA are polymers of nucleotides DNA is a nucleic acid, made of long chains of nucleotides Phosphate group Nitrogenous base Sugar Phosphate group Nitrogenous base (A, G, C, or T) Nucleotide Thymine (T) Sugar (deoxyribose) DNA nucleotide Polynucleotide Sugar-phosphate backbone

• DNA has four kinds of bases, A, T, C, and G Thymine (T) Cytosine (C) Pyrimidines Adenine (A) Guanine (G) Purines Figure 10. 2 B

DNA recap. . answer these. . . 1. An examples of? Polymer 2. Made up of? Nucleotides (deoxyribose, phosphate and base) 3. Different types of bases? Arginine, Thymine, cytosine, guanine 4. Number of strands? 2 5. Held by? Weak hydrogen bonds between strands, covalent bonds between nucleotides (deoxyribose 3’ and 5’) 6. Triplicate code? 3 bases code for an amino acid

RNA • RNA is ribonucleic acid. • It provides a bridge between DNA and protein synthesis. • Like DNA, RNA is also made up of nucleotides. What is a nucleotide? • However the nucleotides in RNA are slightly different! Spot the differences. . .

• RNA is also a nucleic acid – different sugar (ribose – still pentose) – U (uracil) instead of T – Single strand, usually Nitrogenous base (A, G, C, or U) Phosphate group Uracil (U) Sugar (ribose)

RNA The three types of RNA are: – messenger RNA (m. RNA) – ribosomal RNA (r. RNA) – transfer RNA (t. RNA) m. RNA is: – Formed from the DNA in the nucleus. – Small enough to fit through the pores in the nuclear membrane.

m. RNA comtinued. . – – Found in the nucleus and cytoplasm. A “bridge” molecule between DNA and protein. Made by a process called transcription. Made of thousands of bases in 3 s called codons – Transcribe the m. RNA, and split into codons.

m. RNA comtinued. . – – Found in the nucleus and cytoplasm. A “bridge” molecule between DNA and protein. Made by a process called transcription. Made of thousands of bases in 3 s called codons U GUACU GUGC UG

r. RNA – Make up ribosomes with proteins. – Made in nucleolus of nucleus and passed out into cytoplasm via the nuclear pores. – Remain as free ribosomes or attached to endoplasmic reticulum.

t. RNA – – Found only in the cytoplasm. Only 3 bases exposed in 3 D structure General structure of “cloverleaf” Made of two ends • 1 is the anti-codon which binds to a specific m. RNA codon. • 1 is the amino acid binding site.

t. RNA – Specific to an amino acid. – Degenerative code (as more than one codon for an amino acid)

Amino acids – all similar structure with an amino group and a carboxyl acid group, “R” group changes

RNA SUMMARY • 3 types; m. RNA (messenger), r. RNA (ribosomal) and t. RNA (transfer) • m. RNA; carries a copy of the DNA code from the nucleus to the ribosome in the cytoplasm • r. RNA; formed at the ribosome alongside protein • t. RNA; carries an amino acid to the ribosome in the cytoplasm

Gene 1 Gene 3 Process to protein. . DNA molecule Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Polypeptide Amino acid

Transcription • Watch these videos and place the statements in order. . Higher education Scotland Crash course 2. 21 -7. 04. Mc. Graw Hill DNALC

Transcription produces genetic messages in the form of m. RNA nucleotide RNA polymerase 3’ 5’ Direction of transcription Template strand of DNA Newly made RNA

DNA vs RNA • Compare the 2 nucleic acid types.

RNA vs. DNA • RNA contains the sugar ribose; DNA contains deoxyribose. • RNA contains the base uracil; DNA contains thymine instead. • RNA is usually single stranded; DNA is usually double stranded. • RNA is short: one gene long at most; DNA is long, containing many genes.

RNA vs. DNA

RNA 1. Complete the following table to compare RNA and DNA RNA DNA Number of strands 1 2 Found in…. . Nucleus & cytoplasm Nucleus only Sugar present ribose deoxyribose Organic bases G, C, A & URACIL G, C, A & T Number of types 3 1 Length of strand Short Long

Transcription Test 1. How many bases in the genetic code correspond with an amino acid? 2. Draw the section of the m. RNA strand that would be transcribed from section X on the DNA shown. A T G G G C A T A C C C G T A T C G 3. Which enzyme would direct this process? 4. What is the difference between an intron and an exon? 5. What happens to primary transcript of m. RNA? 6. What is the name of this process?

Transcription Test 1. 2. 3. 4. 3, triplicate code Top one, 3’ to 5’ U A C C C G U A U G RNA polymerase Exon is expressed as it is the coding region, intron is non-coding region – polypeptide is fragmented 5. From primary transcript Introns are removed and exons are spliced together to form mature m. RNA 6. RNA splicing

Remember RNA? or ID badges 1. How many types? 2. Location? 3. What are each of their structures (and label within) and functions? 4. Any specific names gives? Lengths?

Remembering RNA. . . http: //www. mfpl. ac. at/rna-biology/rna-history/

RNA m. RNA t. RNA r. RNA Location Nucleus and cytoplasm Cytoplasm Ribosome Lengths Longer 3 bases exposed N/A Structure Codon (from DNA template), made up of introns/exons (exons spliced for mature m. RNA Cloverleaf, 1 Part of ribosome leaf Anticodon with protein (against m. RNA), stalk is amino acid

Learning Outcomes • Review the process of transcription • Describe the process of translation DNA molecule Gene 1 Gene 3 Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Polypeptide Amino acid

Translation Occurs in cytoplasm (mature m. RNA transcript through nuclear pore) on the ribosome (enzymes needed for protein synthesis). 5’ 3’ • Site E; releases (discharges) t. RNA after amino acid (aa) part of polypeptide • Site P – next t. RNA held by H bond to m. RNA • Site A – holds next t. RNA with its aa then peptide linked to previous aa (P)

Translation. . .

Translation • Occurs in cytoplasm (mature m. RNA transcript through nuclear pore) on the ribosome.

Translation 1. A ribosome attaches to the m. RNA at an initiation codon (AUG). The ribosome encloses two codons. 2. met-t. RNA diffuses to the ribosome and attaches to the m. RNA initiation codon by complementary base pairing 3. The next amino acid-t. RNA attaches to the adjacent m. RNA codon (leu in this case) - The codon and anticodon bases matching up

4. The bond between the amino acid and the t. RNA is cut and a peptide bond is formed between the two amino acids. 5 The ribosome moves along one codon so that a new amino acidt. RNA can attach. The free t. RNA molecule leaves to collect another amino acid. The cycle repeats from step 6. The polypeptide chain elongates one amino acid at a time, and peels away from the ribosome, folding up into a protein as it goes. This continues for hundreds of amino acids until a stop codon is reached, when the ribosome falls apart, releasing the finished protein.

Steps in translation SUMMARY 1. Initiation – needs start codon (AUG, for methionine) in P site with anti codon? 2. Elongation – complementary t. RNA bring correct amino acids which are added through a peptide bond 3. Termination A stop codon (AUU, AUC or UGA) which has a release factor which frees the polypeptide from ribosome.

Translation • Multiple translation can occur with many ribosomes reading the same m. RNA – the ribosomes on the same m. RNA are called - polysomes or polyribosome • Translation requires ATP!

What’s happening?

Now explain the WHOLE process

Animate/Model/Demonstrate • Can you animate it? • Anyway possible – here is my original. . .