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67 Cards in this Set
- Front
- Back
DEFINE DNA |
Deoxyribose nucleic acid located in the nucleus controls all the chemical changes in the cells The kind of cell which is formed ( Muscle, blood, nerve) is controlled by the cell The kind of organism produced is controlled by the cell
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DOUBLE HELIX STRUCTURE |
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NUCLEOTIDE |
Phosphate group -PO4 |
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RIBOSE VS DEOXTRIBOSE |
Ribose is a sugar, like glucose, but with only five carbon atoms in its molecules Deoxyribose is almost the same but lacks one oxygen atom |
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ORGANIC BASES |
Adenine - Thymine/Uracil (2 H bonds)
Cytosine - Guanine (3 H bonds)
PURINES Adenine Guanine PYRIMIDINES
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CHARGAFF'S RULE |
-Adenine must pair with Thymine -Guanine must pair with Cytosine -Their amounts in a given DNA molecule will be about the same |
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DNA CHARACTERISTICS |
STRONG bonds between deoxyribose sugar and phosphates WEAK bond between hydrogen and organic bases Weak bond easily breaks when heat is applied
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WHEN DOES DNA SYNTHESIS OCCUR?
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INTERPHASE, Meiosis
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DNA REPLICATION |
-The DNA begins to separate. -Each strand makes a new partner by adding appropriate nucleotides. -Result is there are now two double-stranded DNA molecules in the nucleus. -So when the cell divides, each nucleus contains identical DNA
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REPLICATION #1 |
-DNA polymerase comes onto the scene -HELICASE: UNWINDS the DNA upstream and then UNZIPS the DNA. - This site is known as the replication bubble. |
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REPLICATION #2 |
- Complementary bases begin adding into both sides of DNA - A binds with T, C binds with G (no other possibility because of the shape of the base). |
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REPLICATION #3 |
- The final job of the polymerase is to PROOFREAD the nucleotides after they are added and clip out any that are incorrectly paired. |
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ENZYMES INVOLVED |
HELICASE: unzips and unwinds DNA PRIMASE: begins synthesis of new strands POLYMERASE: joins new nucleotides to the strand LIGASE: 'glues' new nucleotides together. |
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GENETIC CODE |
The sequence of bases (A,T,G,C) |
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WHAT DOES A TRIPLET CODE FOR? |
Amino Acids. The different amino acids and the order in which they are joined up determines the sort of protein being produced. |
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WHAT DO AMINO ACIDS CODE FOR? |
PROTEINS |
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AMINO ACIDS (list) |
-Serine -Cysteine -Valine (C, A, T) -Glycine -Alanine (C, G, A) |
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WHAT DO PROTEINS MAKE? |
-ENZYMES -They also build the cell structure as well as hormones |
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WHAT MAKES UP A GENE? |
A sequence of triplets in the DNA molecule that codes for a complete protein |
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PROTEIN SYNTHESIS |
- Proteins are synthesised by joining amino acids together - Sequence of amino acids that make up different proteins in known by the DNA - Ribosomes in the cytoplasm are the organelles which put together the amino acids, they need sequence form DNA which cant leave nucleus. - 2 distinct processes involved |
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TRANSCRIPTION |
The part of the DNA molecule that the cell wants information from the make a protein unwinds to expose the bases Free mRNA nucleotides in the nucleus base pair with one strand of unwound DNA molecule |
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TRANSCRIPTION |
mRNA copy is made with the help of RNA polymerase. This enzyme joins up the mRNA nucleotides to make mRNA strand. mRNA strand is a complementary copy of the DNA mRNA molecule leaves the nucleus via a NUCLEAR PORE into the cytoplasm |
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TRANSLATION |
mRNA travels to the ribosome mRNA copy attaches to a small subunit of the ribosome in the cytoplasm or ER Transfer RNA (tRNA) exists in the cytoplasm and attaches to amino acids tRNA molecules 'collect' amino acids CODON: group of 3 nitrogenous bases |
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TRANSLATION |
tRNA bons with mRNA via its anticodon. It has an amino acid attached. A second tRNA bonds with the next three bases of mRNA, amino acid joins onto the amino acid of first mRNA via a PEPTIDE BOND Ribosome moves along. First tRNA leaves the ribosome. A third tRNA brings a third amino acid. Stop condon reached. new polypeptide leaves |
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PLASMID |
PLASMID: A circular piece of DNA that exists apart from the chromosome and replicates independently of it |
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WHAT IS RECOMBINANT DNA? |
-DNA that has been cut from one strand of DNA and then inserted into the gap of another piece of DNA that has been broken. - Host DNA often bacteria - Purpose is so the host can produce many copies -Bacteria reproduces in very short time so it is possible to make millions of copies quickly. |
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HOW IS IT MADE? |
-The required gene is cut from the DNA using a restriction enzyme. -Plasmid is removed from bacteria and cut open using same restriction enzyme. -The cut human gene is then mixed with the plasmid in a test tube. -The cut ends of the plasmid and human gene match beause they were cut by the same enzyme, 'STICKY ENDS' - LIGASE sticks ends |
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RE-INTRODUCING PLASMID |
-The plasmid needs to be reintroduced into bacteria so they can multiply the gene -Can be don by combing in a test tube with CaCl2. The high concentration of calcium ions makes bacterial membranes more porous. -Plasmids can now move back into the cells. -Not all bacteria takes up plasmids so this is why monitoring must happen |
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ISOLATING HOST BACTERIA |
-Only want the recombinant DNA -By having a gene on the same plasmid the gives resistance to an antibiotic, the non hot bacteria can be removed by culturing bacteria in a medium of anitbiotic. -The bacteria containing resistance will survive whilst the ones that are not needed will simply die. |
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POSSIBLE IN ALL CELLS? |
-No, will not work in eukaryotic cells -Other methods are used - VIRAL VECTORS: virus injected into DNA of animal host. -GENE GUN: used to insert genes into plant cell |
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EXAMPLES |
1) Insulin for diabetics 2) Wheat crops that are attacked by insects 3) People sick with cystic fibrosis |
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POLYMERASE CHAIN REACTION |
Enables large amounts of DNA to be produced from very small samples. There is a repeating cycle of: SEPARATION of double DNA strands SYNTHESIS of a complementary strand for each |
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4 MAIN COMPONENTS OF PCR DNA |
1) DNA Template 2) Primers 3) Polymerase 4) Buffer Solution |
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3 STEPS OF THERMAL CYCLING |
1) Denature DNA 2) Primer Annealing 3) Extension |
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DENATURE DNA |
-DNA heated to 95C -Breaks weak hydrogen bonds that hold the DNA strands together -Allowing strands to separate creating single stranded DNA |
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PRIMER ANNEALING |
-Mixture cooled to 45-72C -Allows the primers to bind(anneal) to their complementary sequence in the template DNA. |
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EXTENSION |
-Reaction heated to 72C - optimal temperature for DNA polymerase to act -DNA polymerase extends the primers -Adding nucleotides onto the primer in a sequential manner -Using target DNA as a template. |
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BENEFITS OF PCR |
- Can create many copies from a minimal starting amount. - Paternity Test - Recombinant technology |
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GEL ELECTROPHORESIS |
-Techniques used to separate DNA fragments by size. -The gel (agarose) is subjected to an electric charge. -The DNA (negative charge) migrates towards the positive pole. -Larger DNA fragments move slower through the gel matrix -DNA seen using fluorescent dyes |
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WHO WAS ADOPTED? |
S2 Has alleles not present in either parent |
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GENOME |
-An organisms entire genetic make up -Includes all their chromosomes, genes, and DNA |
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HUMAN GENOME PROJECT |
-Set out to identify all the genes in the human genome (about 25,000) and discover the sequence of base pairs (about 2.8 billion) -99% of the gene-containing part of human DNA had been analysed by 2003. |
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MAPPING |
Identification of genes and their positions in the chromosome. Special staining methods reveal bands in the chromosomes. |
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SEQUENCING |
Aims to fond out the sequence of nucleotides in a stretch of DNA Automated to give results quickly Analysis of small piece of DNA to give results like: GCTTATCGATTCCGAT |
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DNA MICROARRAY |
-Allows simultaneous measurement of the level of transcription for every gene in a genome -Microarray detects mRNA |
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MANUFACTURE MICROARRAY |
-Start with individual genes -Amplify all of them using polymerase chain reaction -"spot" them on a medium -Spotting done by robot -Complex and potentially expensive task |
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DEFINE MEIOSIS |
-The form of cell division by which gametes, with half the number of chromosomes, are produced. -Diploid(2n) - Hapliod(n) -Two divisions (meiosis l and meiosis ll) |
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HOMOLOGOUS CHROMOSOMES |
-Pair of chromosomes that are similar in shape and size. Homologous pairs carry gene controlling the same inheritable traits. -Each locus (position of gene) is in the same position on homologues. |
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INTERPHASE |
-Chromosomes replicate -Each duplicated chromosome consists of two identicle sister chromatids attatched at their centromeres -Centriole pair also replicate -CROSSING OVER occurs |
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PROPHASE l |
-Longest most complex phase (90%) -Chromosomes condense -SYNAPSIS: homologous chromosomes come together to form a TETRAD (two chromosomes or four chromatids) |
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METAPHASE l |
-Shortest phase -Tetrad align on equator -Independent assortment occurs 1. Orientation of homologous pair to poles is random 2. Variation 3. Formula 2n |
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ANAPHASE l |
-Homologous chromosomes separate and move towards the poles. -Sister chromatids remain attached at their centromeres. |
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TELOPHASE l |
-Each pole now has haploid set of chromosomes. -CYTOKINESIS occurs and two haploid daughter cells are formed. |
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MEIOSIS ll |
-No interphase (or very short - no more DNA replication) -Meiosis ll is similar to mitosis |
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PROPHASE ll |
-Chromosomes condense -Synapsis occurs, homologous chromosomes come together to form a tetrad. |
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METAPHASE ll |
-Tetrads align on the equator -Independent assortment occurs: 1.Orientation of homologous pairs to poles is random. 2.Variation |
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ANAPHASE ll |
-Homologous chromosomes separate and move towards poles. -Sister chromosomes separate. |
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TELOPHASE ll |
-Nuclei form -Cytokinesis occurs -Four haploid daughter cells produced gametes - sperm or egg |
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CROSSING OVER |
-The exchange of chromosomal segments between two non-sister chromatids -Occurs at one or more points along adjacent homologoues during synapsis -Points contact each other -DNA is exchanged |
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CROSSING OVER BASICS |
-Genes that are far apart have a greater chance of crossing over -Genes that are closer have a less likely chance of crossing over -Genes that stay together are LINKED |
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KINDS OF CROSSING OVER |
1.Single crossing over - only one chiasma is formed. only one chromatid of each chromosome id involved. 2.Double crossing over - Two chiasma are formed. Formed between the same or different chromatids, so 2 or 3 chromatid may be involved 3.Multiple crossing over - More then one chiasma are formed |
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FACTORS AFFECTING CROSSING OVER |
1.HIGH TEMPERATURE - increase frequency 2.X-RAY - increases frequency 3.AGE - decreases frequency |
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DISCONTINUOUS VARIATION |
-Entirely genetically controlled -cannot be altered by external conditions -You either have the condition or you don't -Example- colour blindness, dwarfisim, albanism, sickle cell anaemia |
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CONTINUOUS VARIATION |
-The situation in which there are a great many intermediates between extremes -Example- different shades of hair colour -Variations under genetic control but there are several pairs of genes involved. (genome AA,Bb) |
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DEFINE MUTATION |
A mutation is a spontaneous change in a gene or chromosome. |
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GENE MUTATION |
-Result of faulty replication of DNA -in a nucleotide is not copied right, the triplet will not code for the right amino acid -protein will not function with wrong amino acid -no protein = no enzyme -no enzyme = no functioning orgamism |
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CHROMOSOME MUTATION |
-Result of: Damage to, or loss of chromosome Incomplete separation of chromosomes doubling a whole set of chromosomes i.e. Down syndrome (47 not 46) Klinefelters syndrome (XXY) |