Genes and genomes Flashcards
significance of: Muller
showed X-rays cause mutations in genes, can be intentionally changed
significance of: Beadle and Tatum
used bread mold, which when treated with X-rays could not make enzymes
- conclusion: 1 gene 1 enzyme
define gene: technical
unit of heredity, from parent to offspring and determines some characteristic of offspring
define gene: practical
distinct sequence of nucleotides forming part of chromosomes, which determines order of monomers and thus the polypeptide/ nucleic acid molecule the cell may synthesise
what do genes produce?
- proteins
- RNA: mRNA, tRNA, rRNA
1 gene 1 enzyme hypothesis:
- originally thought 1 gene, 1 protein
- central dogma of molecular biology
outline gene structure: prokaryotes
- control regions
- protein coding regions
prokaryotes: control regions
- determines when gene produces protein
- has promoters (region on DNA where transcription starts)
- other regulatory regions
prokaryotes: protein coding regions
- start codon
- stop codon
- open reading frame (ORF)
outline gene structure: eukaryotes
- control regions
- protein coding regions
- non-protein coding regions
- many eukaryotic genomes are non-protein coding
eukaryotes: protein coding region
exons
eukaryotes: non-protein coding region
introns
human eg. of gene structure
approx. only 1.5% code for proteins
- 8% regulatory (control regions)
alternate RNA splicing
- during transcription, different splicing of exons will translate into different types of proteins
define genome:
the entire genetic complement of an organism
- HOWEVER genome size doesn’t correlate to species complexity
eg. human genome features
- 26 000+ nuclear genomes
- mitochondrial DNA: 17 000 bp
features: gene density prokaryotes
- maximise genomic territory
- gene coding regions very close, even overlap
features: gene density eukaryotes
- evolved other ways for complexity:
- different gene expression
- different gene splicing
- epigenetic factors
non- protein coding genes: features
- pseudogenes non-functional copies of normal genes
- introns within genes
- highly repetitive DNA sequences btw genes (satellites/ microsatellites)
- large regulatory regions (up/downstream)
- structurally: critical regions like centromeres and telomeres
sequencing genomes:
- much cheaper and faster now
- takes DNA, cuts it up, assembles
genome sequencing use:
- from this, can determine evolutionary relationships
- regions of similarity and difference
- genes btw species
- genes which give organisms unique characteristics
