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39 Cards in this Set
- Front
- Back
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Gene Definition |
A section of DNA that contains the coded information for making polypeptides and functional RNA Coded information is in the form of bases along the DNA molecule |
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Why Must There be a Minimum of Three Bases that Coded for Each Amino Acid? (4) |
• Only 20 different amino acids regularly occur in proteins • Each amino acid must have its own code of bases on the DNA • Only 4 different bases are present in DNA • Three bases produce 64 (4 cubed) different codes, more than enough for 20 |
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3 Main Features of the Genetic Code |
• Degenerate Code - Most amino acids are coded for by more than one triplet • Non Overlapping - Each base in the sequence is read only once • Universal - (few exceptions) Each triplet codes for the same amino acid all organisms |
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Locus Definition |
The particular position in which the gene is located on a DNA molecule |
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Other Features of the Genetic Code (4) |
• A few amino acids are coded for by only one triplet • Most amino acids are coded for by between two and six triplets each • Start of the DNA sequence that codes for a polypeptide is always the same triplet (codes for methionine) & it may be later removed if doesn’t form part of final polypeptide • Three triplets don’t code for anything and are called ‘stop codes’ |
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Exons & Introns Definitions |
Exons - coding sequences Introns - noncoding sequences |
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Differences between DNA in Prokaryotic and Eukaryotic Cells |
• Pro - DNA molecules are shorter, circular, and aren’t associated with protein molecules so no chromosomes • Euk - DNA molecules are longer, linear, and occur in association with proteins called histones to form chromosomes & mitochondria and chloroplast have DNA like pro |
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Chromosomes Process (5) |
• When they first become visible at the start of cell division where they appear as two threads joined by single point • Each thread is called a chromatid as DNA has already replicated to give two identical molecules • DNA in chromosomes is held by histones • The length of DNA found un each cell is coiled and folded • Rest of time they’re scattered throughout nucleus |
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DNA Structure Inside Chromosome (2) |
Double helix which is wound around histones to fix it in position, and this is coiled which is then looped and further coiled before being packed into chromosome Chromosomes contains single molecule of DNA that has many genes along its length and each occupies specific position (locus) along molecule |
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Homologous Chromosomes and Pairs |
One of each pair of complete set of chromosomes is provided by the mother in the egg (maternal chromosomes) and the other by the father in the sperm (paternal chromosomes) Total known as the diploid number (45 in humans) |
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What is a Homologous Pair Always? |
Two chromosomes that carry the same genes but not necessarily the same alleles of the gene |
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Allele Definition |
One of a number of alternative forms of a gene |
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What Happens When the Alleles Inherited by Each Parents are Different? |
Each allele has a different base sequence and so a different amino acid sequence which means it produces a different polypeptide |
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What Happens to Any Change in the Base Sequence of a Gene? |
Produces a new allele of that gene (mutation) and results in a different sequence of amino acids being coded for leading to the production of a different protein which may not function properly or work at all |
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Role of mRNA (2) |
Transfers the DNA code from the nucleus to the cytoplasm acting like a ‘messenger’ Leaves the nucleus through the nuclear pores and enters the cytoplasm, where the coded information contained is used to determine the sequence of amino acids in the protein synthesised there |
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Role of mRNA (2) |
Transfers the DNA code from the nucleus to the cytoplasm acting like a ‘messenger’ Leaves the nucleus through the nuclear pores and enters the cytoplasm, where the coded information contained is used to determine the sequence of amino acids in the protein synthesised there |
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Genome Definition |
Complete set of genes in a cell including those in the mitochondria and chloroplasts |
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Role of mRNA (2) |
Transfers the DNA code from the nucleus to the cytoplasm acting like a ‘messenger’ Leaves the nucleus through the nuclear pores and enters the cytoplasm, where the coded information contained is used to determine the sequence of amino acids in the protein synthesised there |
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Genome Definition |
Complete set of genes in a cell including those in the mitochondria and chloroplasts |
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Proteome Definition |
The full range of proteins produced by the genome (complete proteome) or, the proteins produced by a given type of cell under a certain set of conditions |
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Messenger RNA (4) |
•Long, single strand of RNA (single helix) • Created by transcription • Within the cytoplasm it associates with ribosomes and acts as a template for protein synthesis • Posses information in the form of codons (three bases that a complementary to a triplet in DNA) |
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Transfer RNA (5) |
• Relatively small molecule that’s made up of around 80 nucleotides • Single stranded and folded into clover shape • One end extends beyond the other where an amino acid can easily attach • Anticodon is on the other end (sequence of three organic bases) • Each tRNA is specific to one amino acid and has an anticodon that is specific to that amino acid
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What Happens to the Anticodon and Codon during Protein Synthesis? |
An anticodon pairs with the three complementary bases that make up the codon on mRNA |
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Role of tRNA & Why its Well-Suited |
Its end chain for attaching amino acids and its anticodon for complementary base pairings with the codon of the mRNA is structurally suited to its role of lining up amino acids on the mRNA template during protein synthesis |
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Role of tRNA & Why its Well-Suited |
Its end chain for attaching amino acids and its anticodon for complementary base pairings with the codon of the mRNA is structurally suited to its role of lining up amino acids on the mRNA template during protein synthesis |
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Codon Definition |
A sequence of three adjacent nucleotides in mRNA that codes for one amino acid |
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Role of tRNA & Why its Well-Suited |
Its end chain for attaching amino acids and its anticodon for complementary base pairings with the codon of the mRNA is structurally suited to its role of lining up amino acids on the mRNA template during protein synthesis |
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Codon Definition |
A sequence of three adjacent nucleotides in mRNA that codes for one amino acid |
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Anticodon Definition |
A sequence of three adjacent nucleotides on a molecule of tRNA that is complementary to a particular codon on a mRNA molecules |
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Process of Polypeptide Synthesis (4) |
•DNA provides the instructions in the form of a long sequence of bases • A complementary section of this sequence is made in the form of pre-mRNA (process if transcription) • This pre-mRNA is spliced to form mRNA • The mRNA is used as a template to which complementary tRNA molecules attach and the amino acids carried are linked to form a polypeptide (process called translation) . |
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Process of Polypeptide Synthesis (4) |
•DNA provides the instructions in the form of a long sequence of bases • A complementary section of this sequence is made in the form of pre-mRNA (process if transcription) • This pre-mRNA is spliced to form mRNA • The mRNA is used as a template to which complementary tRNA molecules attach and the amino acids carried are linked to form a polypeptide (process called translation) . |
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What is Transcription? |
The process of making pre-mRNA using part of the DNA as a template |
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Process of Polypeptide Synthesis (4) |
•DNA provides the instructions in the form of a long sequence of bases • A complementary section of this sequence is made in the form of pre-mRNA (process if transcription) • This pre-mRNA is spliced to form mRNA • The mRNA is used as a template to which complementary tRNA molecules attach and the amino acids carried are linked to form a polypeptide (process called translation) . |
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What is Transcription? |
The process of making pre-mRNA using part of the DNA as a template |
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Transcription Process (5) |
• Enzyme acts on a specific region of the DNA causing the two strands to separate and expose the nucleotide bases • Nucleotide bases on the template strand pair up with their complementary nucleotides • Enzyme RNA polymerase moves along the strand and joins the nucleotides to form a pre mRNA molecule • As the RNA polymerase adds the nucleotides one at a time to build a strand of pre-mRNA, the DNA strands rejoin behind it • When the RNA polymerase reaches a ‘stop’ triplet code, it detaches, and the production of pre-mRNA is complete |
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Splicing of pre-mRNA (2) |
Occurs in Eukaryotic cells The bade sequences corresponding to the introns are removed and the functional exons are joined together |
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Splicing of pre-mRNA (2) |
Occurs in Eukaryotic cells The bade sequences corresponding to the introns are removed and the functional exons are joined together |
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Translation Process (5) |
• mRNA binds to ribosome • The tRNA molecule with the complementary anticodon pairs with the next codon on the mRNA • Ribosome moves along the mRNA, bringing together two tRNA molecules at a time which pair with the corresponding codons • The two amino acids on the tRNA are joined by a peptide bond using an enzyme and hydrolysed ATP • Continuously moves along mRNA to next codon until reaches a stop codon where it detaches and chain is complete |
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Last Step of Assembling a Protein (3) |
• Polypeptide is coiled or folded to produce its secondary structure • Secondary structure is folded, producing tertiary structure • Different polypeptide chains, along with non-protein groups, are linked to form quaternary structure |
