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39 Cards in this Set
- Front
- Back
Structure of DNA |
•double helix •made of repeating units called nucleotides and link together to form sugar phosphate backbone •nucleotide= deoxyribose sugar, phosphate and base •contains hydrogen bonds between bases •double stranded anti parallel structure • • |
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Base pairing |
Adenine-thymine Guanine-cytosine |
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Deoxyribose at what prime end |
3' end |
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Phosphate at what prime end ? |
5' |
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Type of DNA in prokaryotes |
Circular chromosomal DNA and plasmids |
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Where are circular plasmids found |
Prokaryotes and yeast |
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Where are circular chromosomes found |
Mitochondria and chloroplasts of eukaryotes |
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How are chromosomes arranged in eukaryotes |
Linear chromosomes in the nucleus tightly coiled and packaged with associated proteins |
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How are genotypes determined |
By the sequence of bases |
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Genotype |
Genetic informations of an organism |
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Process of DNA replication |
1. Double helix unwind and weak hydrogen bonds break between base pairs 2.two strands separate, template strands become stabilises and expose their bases at y-shaped replication forks 3. DNA polymerase requires a primer 4.DNA polymerase can only add DNA nucleotides in one direction resulting in one strand being replicated continuously and the other strand replicated in fragments 4. Each fragment has to be primed so DNA polymerase can bind individual DNA nucleotides together 5. Ligase joins the fragments together, this form the lagging strand 6. Each strand twist or into a double helix
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Primer |
A short sequence of nucleotides formed at the 3'end of the parental DNA strand about to be replicated |
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DNA replication requires ? |
•DNA to act as a template • primers • supply of 4 types of nucleotides • enzymes- DNA Polymerase, ligase • ATP |
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Why is DNA replication important ? |
DNA is a molecule of inheritance Ensures an exact copy of a species genetic information is passed from cell to cell during growth and repair and from generation to generation during reproduction |
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PCR |
Technique for the amplification of DNA in vitro |
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Process of polymerase chain reaction |
1. DNA is heated( denaturation 94-96) breaks Hbonds and strands separate 2. Cooling occurs (annealing 50- 65) for primers to bind to complementary target sequence 3. Heat tolerant DNA polymerase replicates the region of DNA by adding nucleotides at the 3'end of original DNA strand 4. Repeated cycles of heating and cooling to amplify this region of DNA |
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Practical applications of PCR |
Tiny quantities of DNA can provide sufficient material for DNA finger printing Paternity testing Diagnosis of genetic disorders |
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Sources of DNA for PCR |
Blood Semen Embryonic cells Viruses Preserved remains of extinct species |
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How is a genotype determined |
Base sequence of the DNA in its genes |
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Phenotype is determined by... |
The proteins produced as the result of gene expression, influenced by intra- and extra- cellular environmental factors |
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What is the switching on of genes controlled by ? |
Transcription and translation. It can also be affected by external environmental factors - only a small no. Of genes in a cell are expressed |
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Gene expression is controlled by |
Regulation of transcription and translation |
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Functions of proteins |
ENZYMES- fold provide shape of active site, they speed up the rate of reactions ANTIBODIES- y- shapes molecules made by white blood cells in response to foreign bodies known as antigens. ( fight off disease) HORMONES- chemical messengers transported in the bloodstream to target tissue. ( e.g. insulin, ADH, HGH) STRUCTURAL PROTEINS- found in cell membrane |
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2 main types of proteins |
Fibrous and globular |
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Structure of mRNA |
Singlestranded, replacement of thymine with uracil and deoxyribose with ribose compared to DNA. |
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Function of mRNA |
mRNA carries a copy of the DNA code from the nucleous to the ribisome |
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What forms the ribisome |
Protiens and rRNA |
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Transcription |
1. Takes place in the nucleus 2.makes mRNA from the base order on DNA 3.the promoter is a region of DNA where transcription is started 4. RNA polymerase is the enzyme which controls transcription |
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Process of transcription: |
1. DNA polymerase moves along the DNA, unwinding and unzipping the double helix and synthesising a primary transcript of DNA from RNA nucleotides by complimentary base pairing ( adenine-uracil, guanine-cytosine) RNA polymerase can only add RNA nucleotides to the 3' end of a growing strand 2. The introns of the primary transcript of mRNA are non-coding regions and are removed in RNA splicing 3. The exons are coding regions and are joined together to form mature transcript. 4.The mature transcript moves out of the nucleus via a nuclear pore into the cytoplasm 5.DNA joins complimentary bases back together with weak hydrogen bonds and winds back I to a double helix |
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Translation |
Takes place in a ribisome Is the translation of mRNA into a polypeptide by tRNA at the ribisome
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Process of translation |
1. A ribisome binds to the 5' end of the mature transcript. This allows the start codon to be in the correct position 2. A molecule of tRNA carrying a specific amino acid becomes attached to the start codon on mRNA. It's anticodon will be complimentary to the codon 3. Weak Hbonds form temporally between the codon and anticodon 4. More tRNA molecules align with their codon 5.peptide bonds form between the amino acids 6.exit of tRNA molecules from the ribisome as polypeptide is formed Start and stop codons exist |
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Purpose of tRNA |
To carry a specific amino acid to the mRNA in the ribisome |
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Structure of tRNA |
Has a triplet anticodon site and an attachment site for a specific amino acid |
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What happens to the tRNA after it has delivered the amino acid to the ribisome |
They are reused, go and collect another amino acid from the cytoplasm |
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How can different proteins be expressed from one gene ? |
Alternative RNA splicing and post transitional modification |
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Alternative RNA splicing |
Different mRNA molecules are produced from the same primary transcript depending upon which segment are treated as introns and exons |
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Post transitional modification |
Protein structure can be modified by cutting and combining polypeptide chains or by adding phosphate or carbohydrate groups to the protein |
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How are proteins held in a three dimensional shape? |
Peptide bonds, hydrogen bonds, folded polypeptide chains and interactions between individual amino acids |
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State the importance of DNA replication to cells |
To ensure each cell has identical DNA |