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45 Cards in this Set
- Front
- Back
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DNA Nucleotides are made up of... |
Deoxyribose sugar Phosphate Base |
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Bases and their complementary partners |
Adenine - Thymine Guanine - Cytosine By hydrogen bonds and double stranded antiparallel structure, with deoxyribose and phosphate at 3' and 5' ends of each strand respectively, formed a double helix |
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DNA is short for... |
Deoxyribose nucleic acid
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Prokaryotes |
Organisms which do not contain a nucleus |
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Features of Prokaryotic genome |
One double stranded, circular chromosome Some have extra circular pieces of DNA called plasmids, consist of DNA sequences genes which are not essential for the existence of the organism but which may be useful for its survival Bacteria - DNA packaged tightly, sometimes along a few associated proteins |
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Eukaryotes |
Their genetic material is inside a nucleus |
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Four groups which make up eukaryotes |
Fungi, protocists, plants, animals |
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Features of a eukaryotic genome |
Several linear chromosomes contained within the nucleus: Mitochondrial and chloroplast DNA Chromosomes in M and C are circular and not wrapped around protein Yeast - they contain plasmids similar to those found in bacteria |
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Replication of DNA stages |
Double stranded DNA to be replicated unwinds The two strands begin to separate (hydrogen bonds break) New nucleotides line up next to complementary bases on the original (template) strands. Hydrogen bonds form between bases. Sugar-phosphate bonds form between neighbouring nucleotides. When the complete DNA molecule has split apart, the result is two identical copies of the parent molecule |
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semi-conservative |
each new molecule of DNA is composed of 1 old strand and 1 new strand |
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DNA polymerase |
forms bonds between nucleotides and links them to the growing DNA strand. Can only start the process if there is a section of double stranded Nucleic Acid present |
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Primers |
Piece of single stranded DNA complementary to a specific target sequence at the 3' end of the DNA strand to be replicated bind to the template and provide DNA polymerase with a double stranded section to which it can add new nucleotides |
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Primers are needed for DNA replication because... |
Needed as the starting block for a new strand for DNA polymerase |
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DNA Ligase |
join fragments of DNA together |
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What are the requirements for DNA replication |
DNA template: provides the code to copy Supply of DNA nucleotides: to produce the new strand of DNA ATP: to provide the enzymes with energy to unwind the DNA Enzymes: DNA P: adds free nucleotides to the new DNA strand in the 5' to 3' end Ligase: join up fragments Primers: TO allow attachment of DNA polymerase |
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Directionality of replication |
strands can only be synthesised in one direction |
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PCR |
method used to produce multiple copies of (amplify) particular DNA sequences (target sequences) which are in short supply |
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Details of the PCR procedure |
At 92 degrees the DNA denatures, hydrogen bonds break and DNA strands separate At 50 - 65 degrees primers bind to DNA strands At 72 degrees Polymerase builds into DNA strands |
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Why must a heat tolerant DNA polymerase be used to replicate the DNA |
Doesn't denature at high temperatures in the PCR process |
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Pratical applications of PCR |
Forensics Paternity tests |
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Positive control |
Give the desired outcome of the experiment |
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Negative control |
Shouldn't give the desired outcome and if results are obtained suggests that something is wrong with the experimental procedure |
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Cells Phenotype |
A cells physical and chemical state is determined by the proteins that are synthesised when the genes are expressed |
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Gene expression |
Controlled by the regulation of transcription and translation Affected by environmental factors acting inside and outside the cell meaning only a fraction of the genes in a cell are expressed |
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Cells genotype |
Is determined by the sequence of the DNA bases in its genes |
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Intracellular signals |
The end product of a chemical reaction switches off an enzyme needed for the reaction to occur |
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Extracellular signals |
Hormones such as insulin switch on genes e.g. to lower blood sugar |
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Why the genetic code is important |
Gene (unit of information) - Amino Acids (building blocks) - Polypeptide (chain of hundreds of amino acids) - protein (large molecule made of folded polypeptide chain/s) |
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RNA nucleotide is made of... |
Base, Ribose sugar and phosphate |
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Differences between RNA and DNA |
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mRNA |
carries the message from nucleus to the cytoplasm |
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rRNA |
combines with protein to form the ribosome |
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tRNA |
brings the amino acids to the ribosomes for assembly into a polypeptide chain Folds back on itself due to base pairing so that 3 exposed bases project from one end of it. |
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process of Transcription |
A section of DNA uncoils and hydrogen bonds break An RNA primer binds to one end of the gene Complementary RNA nucleotides on the template strand The RNA nucleotides bond to one another to form a strand of mRNA The strand mRNA is released and leaves the nucleus through a pore The process is catalysed by RNA polymerase |
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Introns |
of the primary transcript of mRNA are non-coding and are removed in RNA splicing |
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Exons |
Coding regions and are joined together to form mature transcript |
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process of Translation |
tRNA carrying the amino acid specific to its anti-codon pairs up with complementary codon. This is repeated for a second tRNA molecule. The ribosome helps the tRNA bind to mRNA A peptide bond joins the two amino acids together - the first tRNA is released and the ribosome moves along a colon. This process is repeated until a polypeptide chain of about 4000 amino acids has been made |
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triplet of bases known as |
anticodon site |
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What makes up a transfer RNA molecule |
Amino acid attachment site, Hydrogen bond and anticodon |
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Ribosome |
The site of protein synthesis |
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Structure and function of ribosomes |
Small, roughly spherical structures found in all cells Enzymes essential for protein synthesis Function: to bring tRNA molecules (bringing amino acids) into contact with mRNA. 1 binding site for mRNA and 3 binding sites for tRNA |
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Cleavage |
cutting and combining polypeptide chains A single polypeptide chain may need to be cut by enzymes to become active |
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Molecular addition |
Addition of carbohydrate or phosphate groups to the protein A proteins structure may be modified by adding a carbohydrate or a phosphate group to it |
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Cleavage and molecular addition are examples of... |
Post translational modification |
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4 levels of protein structure |
Primary: Secondary: Keratin - strong inelastic Tertiary: any enzyme: very specific shape Quaternary: Haemoglobin: association of oxygen under differing conditions |
