6.1.1 Flashcards
What is mutation
Changes to the base sequence of DNA
What types of mutation are they
Substitution - one or more bases are swapped for another e.g ATGCCT becomes ATTCT
Deletion - one or more bases are removed e.g ATGCCT becomes ATCT
Insertion - one or more bases are added
Define chromosome mutation
Mutation that affect the whole chromosome or number of chromosomes within the cell.
Caused by mutagens and normally occur during meiosis
Define mutagens
Mutagen is a chemical,physical or biological agent that causes mutation
What are the 4 stages that control/regulate gene expression
Transcriptional control
Post-transcriptional control
Translational control
Post translational control
Define promoter and operator
Promoter = DNA sequence located before the structural genes that RNA polymerase binds to Operator = DNA sequence that transcription factors bind to
Define an operon
Group of genes that are controlled by the same promoter
What is a heterochromatin
Methylation makes histones more hydrophobic, tighter packaging, less transcription
What is a euchromatin
Acetylation and phosphorylation reduces the charge on histones, looser packing, more transcription
How are chromatins formed
DNA associated with histone proteins
DNA wraps twice around a bundle of 8 histones from chromatin subunit structure called nucleosome
What is transcription factor in eukaryotes
Factors that bind to specific DNA sequences
Right complex of transcription factors is required for transcription to begin
Increasing or decreasing the production of specific transcription factors, transcription of other genes can be controlled
How can be genes be regulated (detailed)
Transcriptional - genes can be turned on or off
Post transcriptional - mRNA can be modified which regulates translation and types of proteins produced
Translational - translation can be stopped or started
Post translational - proteins can be modified after synthesis which changes their function
What are the post transcription control factors
Product of transcription =pre-mRNA, modified forming mature mRNA
Cap and tail is added- stabilise mRNA and delay degradation
Splicing occurs - introns (non coding DNA) are removed and exons (coding DNA) joined together
Where and explain where RNA editing occur
Post transcriptional
Nucleotide sequence of some mRNA molecules can also be changed via addition,substitution and deletion.
Increases the range of proteins
What are translational control
Degradation of mRNA- more resistant the molecule, longer it will last in the cytoplasm
Binding of inhibitory proteins to mRNA prevents it binding to ribosomes and the synthesis of proteins
What are the post translational control
Addition of non protein groups such as carbohydrate chains
Modifying AA and the formation of bonds such as disulfied bridges
Folding or shortening of proteins
Modification by cAMP
What is the lac operon
Group of three genes involved in the metabolism of lactose. Structural genes as they code for three enzymes
What is the term used to describe the regulation of the pattern of anatomical development
Morphogenesis
Define home box genes
Ancient, highly conversed regions of DNA found in animals, plants and fungi
Code for homeodomains- protein segment that act as a transcription factor
Define hox genes
Specific group of home box genes, only found in animals
Describe the events that occur within E.Colin when lactose is the only respiratory substrate available
When lactose is present, it binds to the repressor, changing the repressors, changing the repressors shape so that it can no longer bind to the operators site
RNA polymerase can now begin transcription of the structural genes
Explain why beta galactosidase and lactose permease are not produced when lactose is absent
The regulatory gene (lacl) produces the lac repressor, transcription factor that binds to the operator site when there’s no lactose present
Blocks transcription because RNA polymerase can not bind to the promoter.
Outline why the majority of mutation do not have an influence phenotype
Mutation is random and the majority of DNA is non coding, mutations in non coding regions do not affect phenotype
Discuss why beneficial mutations are rare and suggest a process that beneficial mutation underpins
Majority of mutations are silent, beneficial mutation increases chances of survival if environment,surviving organisms reproduce and pass new alleles to offspring
