Variation (Recombination) & Mutagenesis Flashcards
Give the mechanisms of cells to prevent & fix mutations.
- proofreading DNA polymerase(s)
- post-replication miss-match repair
- DNA repair by homologous recombination
- cell cycle checkpoints
Describe the formation & repair of UV light-generated pyrimidine dimer.
- occurs between 2 Ts to form a photo dimer
- kink the DNA so no replication or transcription
- in cells photolyase not present
Give the types of chemical mutagens.
-intercalating agents
Insert between base pairs & cause frameshift mutations
-base analogues
Incorporated in DNA in place of normal base causing a mis-pair & base substitution
-base-modifying agents
Covalently alter a base causing a mis-pair & base substitution
Hydroxylating agents add hydroxyl groups
Deaminating agents remove amino groups
Alkylating agents add alkyl groups
Selection is often used by geneticists to isolate rare…
mutants.
Describe the findings of the 1952 Lederberg experiment.
- demonstrated that mutations had occurred before selection.
- mutations are random, whether a particular mutation occurs or not is unrelated to how useful that mutation would be.
When does homologous recombination occur?
Meiosis when DNA is broken & rejoined.
Reciprocal, genetic arrangement used to generate crossovers.
What is lost when homologous recombination repairs double strand breaks?
Heterozygosity.
For 2 linked genes, the recombination frequency is directly proportional to what?
Distance apart.
Describe the process of gene targeting.
- target specific gene for mutation in vivo
- introduce DNA containing homologous sequences & a selectable marker to disrupt the gene
- recombination facilitates the integration of this DNA
- select for cells with the integration (shown by marker)
Describe the particulate theory on how traits are transmitted?
- characters are distinct and hereditary determinants (genes) are particulate in nature.
- each adult has 2 genes for each character; different forms of the gene are called alleles.
- members of the gene pair segregate equally into gametes.
- fusion of the gametes at fertilisation restores the pair of genes and is random.
- different genes assort independently in gametes.
Give the definition of a gene.
Basic unit of biological information, specific segment of DNA that encodes a protein.
Give the definition of genotype.
Alleles at a locus.
Give the definition of an allele.
Alternative forms of a gene.
Give the definition of phenotype.
Observable characteristics.
Give the definition of homozygote.
Identical alleles at a locus.
