Bacterial DNA replication Flashcards Preview

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Flashcards in Bacterial DNA replication Deck (15):
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1. What is the genome, genotype and phenotype of an organism ?

Genome= All of the DNA present in a cell
Genotype= Specific set of genes that an organism possesses
Phenotype= The observable characteristics of an expressed genotype

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2. What is meant by semiconservative replication?

Daughter cells will possess one newly formed strand of DNA and one original strand.

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3. What is meant by bidirectional replication in bacterial cells?

DNA in bacteria (and archaea) is circular. Therefore replication will occur in both directions from an origin point.

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4. How does DNA polymerase work and what does it require?

It catalyzes the synthesis of a complementary strand of DNA in a 5' to 3' direction. It requires a template strand to direct complimentary synthesis, a primer (short length) and dNTPs (deoxynucleotide triphosphates). Forms phosphodiester bonds between bases.

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5. Name 2 other enzymes in =volved in replication and their functions

DNA gyrase: topoisomerase enzyme (undercoiling and overcoiling of DNA), also can negatively supercoil
Primase: synthesises short complimentary strands of RNA to act as primers needed for DNA polymerase.

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6. What are catenanes and how are they resolved?

When two circular dna strands are linked after replication. Topoisomerases decatenate the strands by temporarily breaking them.

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7. What is the function of a template strand?

Acts as a template for the formation of RNA in transcription. (complimentary is called the coding strand as rna will be a replica of this)

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8. What is meant when it is said that bacterial mRNA is Polycistronic ?

Each mRNA molecule codes for more than one polypeptide.

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9. What are the functions of 16s and 23s rna in translation ?

Initiation
16s: binds to the dalgarno sequence on mRNA for protein synthesis
23s: this ribozyme catalyses the peptide bond formation.

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10. What molecule initiates translation ?

N-fromylmethionine = initiator tRNA

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11. What are the three phases of elongation in translation ?

1. Aminoacyl- tRNA binding
2. Transpeptidation reaction
3. Translocation

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12. What are the three sites involved in elongation ?

Peptidyl (donor;p), Aminoacyl (acceptor A) and Exit site (E)

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13. What are stop codons and give the three possible examples?

Stop codons are where termination is initiated in translation. UAA UAG UGA

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14. What is the function of release factors (RF's) and how many are there in bacteria ?

They recognise the presence of stop codons. There are 3 in bacteria.

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15. What are chaperone and secretory systems used for in protein maturation ?

Chaperone molecules assist in the folding of proteins. Secretory systems are used if the protein needs to be exported outside of the cell.