Question

Please help compare and contrast the page attached, thanks!

Assignment: Bacteria versus Eukaryotes

In the space below, compare and contrast the processes of DNA replication, transcription and translation in bacteria and eukaryotes.

DNA replication:

Bacteria                                                             Vs.                                                        Eukaryotes

Transcription:

Bacteria                                                             Vs.                                                        Eukaryotes

Translation:

Bacteria                                                             Vs.                                                        Eukaryotes

Answer 1

DNA REPLICATION:

BACTERIA: DNA replication occurs inside the cytoplasm. There is only one origin of replication per molecule of DNA. Divides by Binary fission. Origin of replication is about 100-200 nucleotides or more in length. Replication occurs at one point in each chromosome. Only one replication fok is formed. Only have one origin of replication. Initiation is carried out by protien DnaA and DnaB DNA gyrase is needed.

EUKARYOTES: DNA replication occurs inside the nucleus. Have many origins of replication in each chromosome. Divides by mitosis Each origin of replication is formed of about 150 nucleotides. Replication occurs at several pointa smultaneously in each chromososme. Multiple replication forks are formed simultaneously in each chromosome. Has multipleorigins of replication. Initiation is carried out by the Origin Recognition Complex. DNA gyrase is not needed.

TRANSCRIPTION:

BACTERIA: Coupled transcription-translation is the rule. Ocurs in cytoplasm There is no definite phase for its occurance A single RNA polymerase synthesises all the three types of RNA(mRNA,tRNA,rRNA) RNAs are released and processed in the cytoplasm. Initiation of transcription does not need any protiens or initiation factors. Pre RNA molecules are released and processed in cytoplasm. RNA polymerases are complexes of five polypeptides. Transcriptional unit has one or more genes The 23s,16s and 15s rRNAs are formed from a single primary transcript.

EUKARYOTES: Coupled transcription translation is not possible. Occurs in the nucleus. Takes place in the G1 and G2 phases of cell cycle. The RNA polymerasesI,II and III synthesizes rRNA,mRNA and tRNA respectively. RNAs are released and processed in the nucleus. Initiation of transcription requires protiens and transcription factors. Pre RNA are released and processed in the nucleus. RNA polymerases are complex to 10-15 polypeptides. Transcriptional unit has only one gene. The 28S,18S,5.8S and 5S rRNAs are formed from two primary trancripts.

TRANSLATION:

BACTERIA: It occurs on 70s ribosomes. It is a continuous process as both transcription and translation occur in cytoplasm. mRNA is polycistronic. First aminoacid take part is fmet. Initition codon is usually AUG, occasionally GUG or UUG. It is a faster process adds about 20 aminoacids per second. It requires three initiation factors IF1,IF2,IF3. After translation, formyl group from first formylated methionine is removed,retaining methionine in polypeptide chain. It requires two release factors RF1(for UAG and UAA) and RF2(for UAA and UGA) in the termination. mRNA life is short(seconds to minutes) as mRNA is less stable.

EUKARYOTES: It occurs on 80s ribosome. It is a discontinuous process as trnscription takes place in nucleus and translation in cytoplasm. mRNA is monicistronic. First aminoacidis met(methioine). Initiation codon is AUG. Occasionally GUG or CUG. It is a slower process that adds one aminoacid per second. It requires a set of 9initiation factors eIF1,2,3,4A,4B,4C,4D,5,6. The whole of initiating methionine is removed from the polypeptide chain. It requires single release factor eRF1. mRNA has a life of few hours to few days.It is quite stable.