DNA and protein synthesis.pptx
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Captioning Statement Video and audio content at the University uses closed captions generated by automatic speech recognition (ASR). The ASR process is based on machine learning algorithms which automatically transcribe voice to text. According to our technology providers this process is approximate...
Captioning Statement Video and audio content at the University uses closed captions generated by automatic speech recognition (ASR). The ASR process is based on machine learning algorithms which automatically transcribe voice to text. According to our technology providers this process is approximately 70-90% accurate depending on the quality of the audio, and consequently video and audio closed captions may include some transcription errors. It is therefore important to recognise that the original recording is the most accurate reflection of the content, and not the captions. If you require accurate captions as part of your reasonable adjustments, please contact the Inclusion Centre to discuss your requirements 26/04/24 1 DNA and Protein synthesis NU1303/NU1401 This topic relates to: Learning outcome: 1 Describe anatomy, physiology and homeostatic mechanisms of human development from conception to old age. Formative and summative assessment Any topic within this module could potentially have a question(s) in the exam paper Links with other topics in the module The cell is the fundamental building block of the whole body. This links with genetics, homeostasis, endocrinology. Links with other modules and stages It is important to understand the cellular level of life for pathophysiologies and psychopathophysiologies. Links to nursing and paramedic practice Many pathophysiologies/psychopathophysiologies and their treatment are linked to the cellular level. 26/04/24 3 Chapter 4 CHARLES J. WELSH 2021 HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fourteenth Edition 26/04/24 4 4.5: DNA (Deoxyribonucleic Acid) Deoxyribonucleic acid (DNA): Contains the genetic code, the instructions needed for the synthesis of each protein (including enzymes) required by the cell Genetic Information: A gene is a portion of a DNA molecule that contains the genetic information for making a single protein The complete set of genetic instructions for an organism is the genome The portion of the genome that encodes proteins (only about 1.5%) is the exome The rest of the genome regulates the activation of genes for protein synthesis DNA Molecules DNA molecules consist of building blocks called nucleotides The nucleotides of DNA form 2 sugar-phosphate backbones, with bases extending into the interior of the DNA molecule, which gives DNA a twisted ladder-like appearance The bases found in DNA nucleotides are adenine (A), guanine (G), cytosine (C), and thymine (T) The bases are joined to each other by weak hydrogen bonds The nucleotides of one DNA strand exhibit complementary base pairing with those in the other strand (adenine pairs only with thymine; cytosine only with guanine) The DNA molecule twists to form a double helix, and may be millions of base pairs long DNA Structure DNA Replication 1 Each new cell must be provided with an exact replica of the parent cell's DNA DNA replication (copying) occurs during interphase: The DNA double helix separates by breaking the hydrogen bonds between the base pairs Double helix unwinds and strands come apart DNA polymerase brings new nucleotides to each strand, which form complementary pairs with the original strands Other enzymes join the sugar-phosphate backbones together Each new DNA molecule consists of one parental strand and one newly-synthesized strand DNA Replication 2 4.6: Protein Synthesis DNA supplies genetic instructions for making proteins The genetic code is the sequence of base pairs in a gene that specifies the order of amino acids to make a particular protein An amino acid is represented by a specific sequence of 3 nucleotides on DNA In the genetic code, nucleotide sequences also represent “start” and “stop” messages for each gene The process of protein synthesis requires two sequential steps: transcription and translation Transcription 1 DNA molecules cannot leave the nucleus, but protein synthesis occurs in the cytoplasm Therefore, the genetic information is copied onto a molecule of RNA, which is shorter than DNA and can leave the nucleus RNA molecules differ from DNA in the following ways: they are single-stranded, contain ribose rather than deoxyribose, and contain uracil instead of thymine The synthesis of messenger RNA (mRNA) molecules in the nucleus, in a sequence complementary to the DNA template strand, is called transcription Transcription 2 The enzyme RNA polymerase directs the synthesis of mRNA, according to the rules of complementary base pairing RNA polymerase also recognizes the beginning and end of a particular gene, and which DNA strand is the proper one to copy When the enzyme reaches the end of the gene, it releases the new mRNA strand; this completes the process of transcription A Comparison of DNA and RNA Molecules TABLE 4.1 A Comparison of DNA and RNA Molecules DNA RNA Main location Part of chromosomes, in nucleus Cytoplasm 5-carbon sugar Deoxyribose Ribose Basic molecular structure Double-stranded Single-stranded Nitrogenous bases included Adenine, thymine, cytosine, guanine Adenine, uracil, cytosine, guanine Major functions Replicates prior to cell division; contains information for protein synthesis mRNA carries transcribed DNA information to cytoplasm and acts as template for synthesis of protein molecules; tRNA carries amino acids to mRNA Complementary Base Pairs TABLE 4.2 Complementary Base Pairs Complement ary strands of a DNA molecule Complement ary strands of a DNA molecule Transcribed Complementa strand of ry strand of DNA mRNA A T A U T A T A C G C G G C G C Translation 1 Each amino acid corresponds to a three-base sequence of DNA nucleotides; in the complementary mRNA, this sequence is called a codon One codon represents a “start” message (at the beginning of a gene), and three represent “stop” messages (to signal the end of a gene) mRNA moves out of the nucleus and associates with a ribosome in the cytoplasm, where the protein will be constructed in a process called translation In the cytoplasm, another type of RNA, transfer RNA (tRNA), has a three-base sequence of nucleotides called the anticodon, which is complementary to nucleotides of the messenger RNA codon Translation 2 The ribosome holds the mRNA in position, while the tRNA carries in the correct amino acid in sequence, with anticodons matching up to codons Since there are 20 different types of amino acids, there are different types of tRNA for each amino acid The ribosome contains enzymes needed to join the amino acids together by dehydration synthesis As the amino acids are joined to each other, the new protein molecule folds into its unique shape, or conformation Codons (mRNA Three-Base TABLE 4.3 Codons (mRNA Three-Base Sequences) Sequences) SECOND LETTER U SECOND LETTER C SECOND LETTER A SECOND LETTER G FIRST LETTER U UUU: phenylalanine (phe) UCU: serine (ser) UAU: tyrosine (tyr) UGU: cysteine (cys) THIRD LETTER U FIRST LETTER U UUC: phenylalanine (phe) UCC: serine (ser) UAC: tyrosine (tyr) UGC: cysteine (cys) THIRD LETTER C FIRST LETTER U UUA: leucine (leu) UCA: serine (ser) UAA: STOP UGA: STOP THIRD LETTER A FIRST LETTER U UUG: leucine (leu) UCG: serine (ser) UAG: STOP UGG: tryptophan (trp) THIRD LETTER G FIRST LETTER C CUU: leucine (leu) CCU: proline (pro) CAU: histidine (his) CGU: arginine (arg) THIRD LETTER U FIRST LETTER C CUC: leucine (leu) CCC: proline (pro) CAC: histidine (his) CGC: arginine (arg) THIRD LETTER C FIRST LETTER C CUA: leucine (leu) CCA: proline (pro) CAA: glutamine (gln) CGA: arginine (arg) THIRD LETTER A FIRST LETTER C CUG: leucine (leu) CCG: proline (pro) CAG: glutamine (gln) CGG: arginine (arg) THIRD LETTER G FIRST LETTER A AUU: isoleucine (ile) ACU: threonine (thr) AAU: asparagine (asn) AGU: serine (ser) THIRD LETTER U FIRST LETTER A AUC: isoleucine (ile) ACC: threonine (thr) AAC: asparagine (asn) AGC: serine (ser) THIRD LETTER C FIRST AUA: isoleucine (ile) ACA: threonine AAA: lysine (lys) AGA: arginine THIRD Protein Synthesis Protein Synthesis on the Ribosomes Translation 3 Correct protein folding is required for good health, and the functioning of the protein Misfolded proteins are either refolded or destroyed by spool-shaped structures called proteasomes A gene that has been transcribed and translated into a protein is said to be expressed Gene expression is the basis for cell differentiation
