Topic 6 Flashcards
DNA replication, mutation & expression
When DNA is replicated why is it in a semi-conservative manner?
- 1 strand will be from the original template molecule
- 1 strand will be newly synthesised
- process of replication, where resulting double helix composed of both old strand + new strand
What is the process of DNA replication as it is discontinuous and initiated with RNA primers?
- during DNA replic, DNA + RNA primers removed from lagging strand of DNA to allow Okazaki fragments to create + bind to lagging strand
- once template becomes discontinuous, create an Okazaki fragment (short sequences of nucleotides)
Define the term mutation.
- replication without repair
- physical change introduced into DNA
- mutations within DNA region encoding protein (gene) may cause abnormal protein to be produced
What is spontaneous mutations?
- non-induced
- damage from unknown cause
- may occur frequently in organisms w/ short generation times
What is induced mutations?
- exposure to mutagens (agents that increase rate of mutations)
- may purposely induced for research purposes:
- chemical: NSG
- biological: virus
- physical: gamma rays
- natural mutagens eg radon, UV light
- human created mutagen eg asbestos, nuclear fall out
What is somatic mutations?
- mutations in body cells
- may affect entire developmental process of organism or particular region
Whta is germinal mutations?
- mutations in gamete cells (eggs & sperm)
- mutated gametes passed => offspring
What is the difference between spontaneous, induced, somatic and germinal mutations?
- spontaneous: non-induced
- induced: any change in DNA sequence that can be passed parent => offspring
- somatic: mutation in body cell of organism
- germinal: mutation in gamete cells
What are the different types of mutations and their effects?
- gross (change in chromosomal structure)
- point (single nucleotide)
- frameshift (indels of a number of nucleotides)
- missense
- nonsense
- silent
What is the process of transcription in prokaryotes?
- monocistronic or polycistronic
What is lac operon?
- group of genes (operon) with single promoter (transcribed as a single mRNA)
- genes in operon encode proteins that allow bacteria to use lactose as an energy source
How is gene expression controlled through actions of regulatory proteins?
- regulatory protein encodes for a repressor protein important for regulating gene expression
- if repressor binds to operator site, polym. => promoter + gene expressed as gene read + protein made
What are some of the similarities and differences between gene control in prokaryotes and eukaryotes?
PRO: - no role of chromatin - operon control - alll genes transcribed by single RNA polym. - RNA splicing rare EUK: - role for chromatin - operon control rare - 3 RNA polym. function - RNA polym. I (for mRNA) much larger + more complex - RNA splicing common
What is the enzyme that unwinds DNA?
DNA helicase
What are different types of gross mutations? (chromosomal structural change & number)
- insertion/deletion
- duplication
- inversion: 180° rearrangment
- polyploid: change in entire chromosomal set, more than 2 sets
- aneuploidy: change within chromosomal set, addition/deletion
What are different types of point mutations? (single nucleotide)
TRANSITION:
- base substitution: purine ⬌ purine, pyrimidine ⬌ pyrimidine
- transversion: purine ⬌ pyrimidine
INDEL:
- insertion/deletion of bases
EXPANDING GENES:
- some genes repeat base sequences and may increase with each generation
- cause of muscular dystrophy, Huntington’s
What is frameshift mutation?
addition/subtraction change to framework - effect on coding region
What is missense mutation?
substitution of different aa for another
What is nonsense mutation?
results in insertion of stop codon
What is silent mutation?
point mutation that do not change protein sequence
What does lacZ, lacY and lacA genes code for in lac operon?
lacZ:
lazY:
lazA:
What does structural genes lacZ, lacY and lacA code for in lac operon?
lacZ: codes for enzyme β-galactosidase that hydrolyses lactose => glucose + galactose
lazY: codes for enzyme galactoside permeate, involved in uptake of lactose
lacA: codes for transacetylase, transfers acetyl group to lactose as taken up by cell
How is lac operon regulated?
- addition of lactose enable lac operon
- inducer binds to regulator, preventing lacI from binding
What is regulatory lacI gene?
- regulatory gene
- encodes for protein that regulates gene expression
