Protein Synthesis and DNA Replication PDF

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Summary

Summary of Protien Synthesis and DNA replication...

Description

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NUCLEIC ACIDS

o C, H, O, N, P o Nucleotides monomer unit of nucleic acids. o All bonds are covalent bonds. o

Nitrogenous Base Pentose sugar (5 carbon sugar – deoxyribose or ribose in RNA) Phosphate group Nucleic Acid DNA Contains genetic material inherited from generation to generation. Codes for protein synthesis. Bases work in triplets. Polypeptide determined by code in the DNA. Is universal therefore can be used inter-

Description -

Deoxyribose sugar Double stranded , bases held by hydrogen bonds Double helix strands twist around each other. Spiral. Inheritable genetic material Strands are anti-parallel. One side, nucleotides join 3 prime to 5 prime, and other side is 5 prime to 3 prime. This plays a role in determining complementary base pairing.

Complementary Bases A–T G–C

species. RNA

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Makes a copy of information in the DNA which is then used to make proteins.

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A–U Ribose sugar Single stranded but can fold over G – C itself to look like double stranded. Uracil and adenine

mRNA (messenger) Makes complementary copy of code in DNA. tRNA (transfer) Bring specific amino acids to ribosome and translate code on mRNA

rRNA (ribosomal) forms ribosomes

More energy to separate guanine and cytosine

Protein Synthesis 1. Genetic code in DNA copied into mRNA molecule. 2. Base sequence in coding strand of DNA is copied to mRNA using complementary bases (by transcription) 3. Triplets of bases in DNA transcribed into codons in mRNA - each codon codes for specific amino acid in polypeptide product. 4. mRNA molecules translated at ribosomes by tRNA.

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CHAPTER 11 – DNA/RNA

DNA (deoxyribonucleic acid) o Contains inheritable genetic material that codes for proteins. - Monomer unit: Nucleotides which contain CHONP and Phosphate group, Pentose Sugar, Nitrogenous base. Base Pairings: GC, AT -

Purine Bases: Guanine and Adenine Pyrimidine Bases: Cytosine and Thymine/Uracil

RNA (ribonucleic acid) o Largely involved in protein synthesis.  Usually single stranded  Ribose sugar and Uracil replaces Thymine.  Viruses can have double stranded RNA. Base Pairings: AU, GC mRNA: Carriers genetic material to ribosomes for protein synthesis. rNA: Forms part of ribosome. tRNA: Assists in protein synthesis by transferring amino acids to ribosomes.

Nucleotide Structure

 Nitrogenous base: holds the complementary base pairings.  Pentose sugar: 5 carbon deoxy- or ribose sugar

 Phosphate: Carbon attaches to 5 prime carbon. Phosphate of next nucleotide binds to 3 prime carbon  Hydrogen bonds between base pairs. Antiparallel strands: DNA base pairings run in opposite directions from each other - 5 prime and 3 prime as opposed to 3 prime and 5 prime.

Hybridization o When you create dna from two separate sources and stick together.  Similar code and base pairing.  Complementary base sequences.

Apoptosis o Programmed cell death.  If undeveloped, too many cells or not useful  Triggered by Tc cells and Natural Killer cells  Compartments of cytoplasm and membrane from cell. Phagocytes come and engulf the leaked contents

ATGCCGTTAGCTAAGGTC (template – read by enzymes that make mrna that is complementary ) TACGGCAATCGATTCCAG (coding strand – complementary to template and goes from 5’ – 3’. Has same sequence as mRNA except it contains T whilst mRNA contains U)

Transcription(nucleus) DNA to mRNA o Creation and modification of complementary mRNA sequence of DNA from a DNA template strand.  RNA polymerase attaches to and moves along DNA, creating pre-mRNA)  Upstream to downstream of gene

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Proteins upstream of gene regulate gene expression mRNA engages with ribosomes to begin translation in protein synthesis. Complementary mRNA sequence to template strandUACGGCAAUCGAUUCCAG

Post-Transcriptional Modification

o Pre-RNA is modified to form a mature mRNA  Exon: coding region of gene. Contains info made into protein via transcription. 

Introns: Non-coding DNA is removed through splicing. This allows exons to bind to form final mRNA which carries correct order of nucleotides for protein to be formed.

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5’ cap is added: proteins that help mRNA leave the nucleus. Poly(A – ADENINE) added to 3’ end of mRNA (enzymes)

UACGGCAAUCGAUUCCAG (pre mRNA) UAC GGC AAU CUC CAG (mature mRNA) TYR – GL Y – ASN – LEU – GLN (amino acid chain)  Making more stable 1. Methylated cap added to 5’ end to enable translation of the mRNA at ribosome. Plays a role in ribosomal recognition of mRNA during translation into protein. 2. Poly-A-Tail (containing Adenine nucleotides) added to 3’ end to make mRNA resistant to degradation. Enables mRNA to exit nucleus. Translation Synthesis of polypeptide using mRNA as a template.  Occurs in the cytoplasm.  Necessary components: Mature mRNA, ribosome, tRNA (amino acid complexes)  Mature mRNA template to amino acid

1. mRNA moves through ribosome and read in groups of 3 nucleotides (codons) 2. tRNA carry an anticodon which binds to codon. It carries a specific amino acid which is put in correct position in growing polypeptide. Codon = 3 base in mRNA // 3 bases in DNA or RNA, each codon corresponds. Anticodon = complementary to codon and is attached on tRNA only. Amino acid to ribosome (tRNA) single stranded. tRNA is complementary to mature mRNA codon complementary to mature mRNA to a single amino acid. 64 codons – 64 in DNA and RNA each Multiple codons can go to 1 amino acid

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CHAPTER 11 – DNA Replication

Enzyme makes complementary base pairing DNA Replication o Semi conservative: molecule we use to copy or use as template is used as part of a new molecule. Half is from strand half Is the new synthesized molecule. o Occurs during synthesis phase of cell cycle.

Components of DNA Replication  DNA Polymerase - Makes a polymer – DNA  Okazaki fragments – short, new DNA sections, complementary to lagging template strand. Joined by DNA ligase.  Helicase – BREAK HYDROGEN BONDS ACROSS DOUBLE STRANDED DNA INTO TWO SINGLE STRANDED dna AND CREATING REPLICATION FORK(GOING UP AND GOING DOWN)

 Dna ligase sticks fragments together and adds  DNA polymerase  Lagging strand: Complementary to okazaki fragments. Replicates them into leading strand. (discontinuous)  Leading strand: continuous replication (from 3’ to 5’ direction)  RNA Primer Process o Involves many enzymes that have specific roles. - Requires energy 1. DNA helicase assists in the separation of the two DNA strands (Structure R – parent strand; Structure S – template strand) of the double helix at replication origins, which results in the formation of replication forks (Feature Q). 2. DNA polymerase moves along Structure R (parent strand) starting at the 3’ end and moving toward the 5’ end / Feature Q; Structure U (the leading strand of daughter DNA) is formed. Simultaneously, Structure T (Okazaki fragments) forms, moving away from Feature Q. 3. Fragments of Structure T (Okazaki fragments) are joined by DNA ligase to form a continuous strand, hydrogen bonds form between parent–daughter strands producing two semi-conservative strands of DNA.

PROKARYOTES – DNA circular Adds complementary nucleotides to form dsDNA Adds nucleotides from 3’ growing end and travel to 5’ (it forms 5’ to 3’)

How many DNA molecules after a number (n) of divisions? o 2 to the power of (n)

Types of DNA Mutations

Substitutions (Missense)  Nucleotide transforms codon into stop codon – premature termination of translation affecting formation of proteins. Silent Substitution  Change in nucleotide base has no outward effect. Insertion/Deletion  Also called frame-shift mutation.  Affects every codon in a genetic sequence....