9. Gene Flashcards
Definition of:
- gene
- coding region
- non-coding region
Gene:
- > nucldt sequence of DNA/RNA molecule
- codes for AA sequence of a protein (=coding sequence)
- or controls where and when a protein is produced (=regulatory sequence)
Coding region:
- Sequences coding for the AA sequence of a protein
- Bacterial genom: 98% of DNA is coding
Non-coding region:
- Regulatory sequences
- Sequences binding to RNA-polymerase
- Sequences binding to transcription factors
- Introns (does not comprises genes)
- human genom: 98% of DNA is non-coding
Definition of junk DNA
- > region, wh do not code for proteins or regulate expression of genes
- constitute to 95% of human genome
- involved in evolution of new genes
- “seat” of crucial gene-controlling activity
Genes in Prokaryotes and Eukaryotes
Genes in prokaryotes:
- are intronless, uninterrupted
- are complementary to their corresponding mRNA
- are not amplified and have coding function only
- DNA is circular and accessible
- some genes overlap
Genes in eukaryotes:
- are split –> divided by long intergenic regions (non-coding seq./introns) and exons
- are not complementary to the mature mRNA
- are amplified in a tandem manner
- DNA is linear and packed in chromatin
Repetitive DNA (Def., types)
-> repeated seq — patterns of DNA or RNA that occur in multiple copies through out the genome
- Single copy DNA seq (60% of total):
- present in single or low copy numbers
- code for structural genes and all proteins except histones - Moderately repetitive DNA seq (30%)
- present at 100.000 copies per genome
- code for histones, actin, myosin, hemoglobin, r and tRNA - Highly repetitive DNA seq. (10%)
- present at 1mio. copies per genome
- roles in chrms pairing, cross-over or recombination
Types of genes — depending on their regulation
- constitutive genes — transcribed continually
- facultative genes — transcribed only when needed
- housekeeping genes — constitutive genes transcribed at a relatively constant level -> needed for maintenance of the cell
- inducible genes — their expression is either responsive to environmental changes or dependent on the position in the cell cycle
Types of genes — depending on their functional activity
- Active genes:
- Found in euchromatin
- Constant transcription and translation - Repressed (temporarily inactivated) genes:
- Found in facultative heterochromatin
- Expressed in a particular moment dependent on cellular needs - Blocked (constantly inactivated) genes
- Found in structural heterochromatin
- Never expressed
- Present in highly specialized cell types
Types of genes — depending on function of proteins their encode
- structural genes – encode structural proteins
- regulatory genes– encode proteins that regulate the expression of structural
- oncogenes – encode oncogenic proteins
Single nucleotide polymorphisms (SNPs)
Genetic polymorphism:
-> mutation in a gene or chrmsmal locus
SNPs:
- > a single ncltd in genome differs among different individuals within the same species
- are 90% of all genetic variations in humans
- 2/3 are substation of cytosine through thymine
- appear in introns and exons
- not harmful in normal conditions (can even have positive effects like tolerance of lactose, longevity)
Significance of SNP
- may cause altered proteins
- predisposition to diseases like leucemie, Alzheimer
- genomic technologies which identifies SNPs and enhance their disease susceptibility
Def. of Gene expression & regulation
+ Function and characteristics of Gene regulation
Gene expression:
process by which gene’s information is used in synthesis of functional gene product
Gene regulation:
-> control amount and timing of appearance of functional gene product
Function of GR:
- Control of insulin, cyclins(protein,regulate cell cycle)
- control of gene dose
- provides cellular flexibility and adaption
(In general-> provides control over all structure and function)
Characteristics?
- Transcriptional
- Post-transcriptional
- miRNAs
- Translational
- Post-translational — protein degradation
Pseudogenes
- genes, wh do not code for functional protein
- play role in cancerogenesis (e.g. PTEN-gen)
Central dogma
Def: explanation of flow of genetic information within biological system. Often stated as “DNA makes RNA and RNA makes protein”
General Types:
- Replication (DNA -> DNA)
- Transcription (DNA -> RNA)
- Translation (RNA -> Protein)
Special Types:
- RNA-Replikation (RNA-> RNA) — e.g RNA-Viren
- Reverse Transkriptase (RNA-> DNA) — e.g. in eukaryotes through telomerase
