SABS I Lecture 5: Basic Cell Genetics and Molecular Biology

replication

DNA to synthesis of DNA

transcription

DNA to synthesis of RNA

translation

RNA to synthesis of protein

central dogma

DNA to RNA to protein

- RNA viruses replicate their RNA

- Retroviruses use reverse transcriptase to make DNA from RNA

two exceptions to the central dogma and what they do instead

binary fission

most bacteria replicate using this method

mitosis

cell replication in which 2 daughter cells have genetically identical information

meiosis

cell replication in which 4 daughter cells have half the genetic information with a mixture of genes in each

cytoplasm

where chromosomal replication occurs in prokaryotes

one circular chromosome with single origin of replication (oriC)

chromosome type and origin of replication in prokaryotes for chromosomal replication

several linear chromosomes with multiple origins of replication per chromosome

chromosome type and origin of replication in eukaryotes for chromosomal replication

DNA polymerases I and III (III is primary DNA polymerase)

DNA polymerases for prokaryotes in chromosomal replication

multiple DNA polymerases

DNA polymerases for eukaryotes in chromosomal replication

yes

Is a gyrase (topoisomerase) required in chromosomal replication of prokaryotes?

no

Is a gyrase (topoisomerase) required in chromosomal replication of eukaryotes?

rapid - 2000 bp/sec

speed of chromosomal replication in prokaryotes

slow - 100 bp/sec

speed of chromosomal replication in eukaryotes

- template recognition

- initiation

- elongation

- termination

four steps of chromosomal replication

bidirectional

one starting point and moves outward in two opposite directions at the same time; chromosomal replication is this

semiconservative

original strand with a new complimentary strand; chromosomal replication is this

sugar and phosphate backbone

backbone of DNA

- guanine

- cytosine

- thymine

- adenine

4 bases in DNA

5' to 3'

DNA replication direction

leading strand

synthesized continuously in the 5' to 3' direction

lagging strand

synthesized in Okazaki fragments which are connected by DNA ligase

prokaryotes

in _______________, transcription occurs simultaneously with translation

eukaryotes

in ______________, transcription is independent of translation

cytoplasm

where transcription occurs for prokaryotes

nucleus

where transcription occurs for eukaryotes

1

How many RNA polymerases do prokaryotes use for transcription?

3

How many RNA polymerases do eukaryotes use for transcription?

no

Is the transcript modified in prokaryotes during transcription and how?

yes, 3' and 5' modifications and splicing into mature mRNA

Is the transcript modified in eukaryotes during transcription and how?

5' to 3'

direction of reading of codons in translation

genetic code

a code that is universal, redundant, and has nonsense (stop) codons

70S ribosomes with 30S and 50S subunits

ribosomes and subunits in prokaryotes for translation

80S ribosomes with 40S and 60S subunits

ribosomes and subunits in eukaryotes for translation

3 types: 5S, 16S, 23S

types of rRNA in prokaryotes for translation

4 types: 5S, 5.8S, 18S, 25S

types of rRNA in eukaryotes for translation

Shine-Dalgarno sequence (special ribosome-binding site on mRNA)

translation initiation for prokaryotes

binding of ribosome to 5' cap of mRNA and scanning for start codon (NO Shine-Dalgarno sequence)

translation initiation for eukaryotes

initiation, elongation, termination factors

factors used for translation in prokaryotes

initiation, elongation, termination factors that are more numerous/complex

factors used for translation in eukaryotes