DNA, Genes And Protein Synthesis

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What is a gene?
A gene is a section of DNA that contains the coded information to make polypeptides and functional RNA.
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What make up proteins?
Polypeptides make proteins, so genes determine the proteins of an organism.
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What are enzymes?
Enzymes are proteins. They control chemical reactions so are responsible for an organisms development
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What is Locus?
The position of gene on a DNA molecule/chromosome
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A gene is a base sequence of DNA that codes for?
The amino acid sequence of a polypeptide or functional RNA (rRNA and tRNA)
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How many bases code for an amino acid?
Three
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How many amino acids reguarly occur?
20
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Name the 4 DNA bases?
Adenine, thymine, guanine and cytosine
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What are the three bases together called?
Triplet
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Is the code overlapping or non-overlapping?
Non-overlapping
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What are coding sequences called?
Exons
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What are non-coding sequences called?
Introns
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What are the differences between Prokaryotic and Eukaryotic cells?
Prokaryotic cells have shorter DNA that forms a circle. they are also not associated with protein synthesis so do not have chromosomes. Eukaryotic cells have a longer DNA molecule in a line, that combine with histones to form chromosomes.
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How are chromosomes formed?
A DNA, a molecule formed of nucleotides, DNA combines with histones, the DNA histone complex becomes coiled. The coils then fold to form loops. The loops then coil and pack together to form a chromosomes.
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What is a homologous pair?
A pair of chromosomes that have the same gene loci, so determine the same features.
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What is the diploid number?
The total number of chromosomes in an organisim.
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What is an allele?
One of a number of alternative versions of a gene.
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What is a mutation?
A sudden change in the amount or arrangement of the genetic material of a cell.
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Where does the synthesis of proteins occur?
The cytoplasm
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How does mRNA leave the nucleus?
Through the nuclear pore into the cytoplasm
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What does the word 'codon' refer to?
The sequence of three bases on mRNA that codes for a single amino acid
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What does Genome mean?
The complete set of genes in a cell, including those in mitachondria and chloroplasts.
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What is a Proteome?
The full range of proteins produced by the genome. This can be reffered to as the complete proteome.
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What is RNA?
A polymer made up of repeating mononucleotide sub units.
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What is RNA made of?
A pentose sugar (ribose sugar), a phosphate group and a nitrogenous base.
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What is the structure of mRNA?
A long strand arranged in a single helix.
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How does mRNA leave the nucleus?
Via the nuclear pore in the nuclear envelope and enters the cytoplasm where it associates with ribosomes.
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What is the function of mRNA?
It acts as a template for protein synthesis - because it possesses information in codons. The codons determine the amino acid function.
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What is the structure of tRNA?
A relatively small molecule made up of around 80 nucleotides. It is a single stranded chain folded into a clover leaf shape.
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What are the functions of mRNA?
Each type of tRNA binds to a specific amino acid and many are coding triplets. tRNA is however specific to one amino acid which its anti codon is specific to.
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What organic bases pair together?
Adenine and Thymine or Uracil and Cytosine with Guanine
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What is pre-mRNA and what is it used for?
A complementary section of a long sequence of bases that is used in transcription. It is spliced to form mRNA.
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What is Transcription?
The process of making mRNA using part of DNA as a template.
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What is the first step of transcription?
1. RNA polymerase attatches to DNA double helix at the begining of a gene.
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What is the second step of transcription?
Hydrogen bonds between two DNA strands break, meaning the strands are seperated. The DNA molecule uncoils to expose bases.
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What are the third and fourth steps of transcription?
One of the strands is a template for mRNA. RNA polymerase lines up free nucleotides alongside free bases, the bases and nucleotides are attracted so coplementary base pair so the mRNA is a complementary copy.
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What is the fifth step of transcription?
Once RNA nuclotides have paired with the DNA bases, they are joined together by RNA polymerase to form mRNA.
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What is the sixth step of transcription?
RNA polymerase moves along DNA, seperating strands to make mRNA.
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What are the seventh and eighth step?
Hydrogen bonds between uncoiled DNA reform so the strands recoild into a double helix. Then when RNA reaches a particular sequence a stop codon cause mRNA to stop being produced and the sequence breaks off.
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What is the final step of transcription?
mRNA moves out of the nucelus through the nuclear pore and attatches to a ribsome in the cytoplasm.
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What is Translation?
Where amino acids are joined together to make a polypeptide chain.
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What is the first stage of translation?
mRNA attatches itself to a ribosome and tRNA carries amino acids to it.
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What is the second stage of translation?
tRNA carrying an amino acid with an anticodon, this is complementary to the first RNA codon by specific base pairing.
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What are the third and fourth stages of translation?
A second tRNA molecule attatches to the next codon on the mRNA. The two amino acids attached to tRNA are joined by a peptide bond. The first tRNA molecule moves away leaving an amino acid.
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What is the fifth stage of translation?
A third tRNA molecule binds to the next mRNA codon. Its amino acid binds to the previous and the second tRNA molecule moves away.
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What is the sixth stage of translation?
The process continues to form a polypeptide chain until there is a stop codon.
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What is the final stage of translation?
The polypeptide chain moves away and the process is complete.
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Card 3

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Card 4

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Card 5

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