Genes and Mutations
1. Define:
Genetics - Genetics may be defined as the science or study of heredity, and is concerned with the physical and chemical properties of the genetic material (DNA or RNA), how this material is transmitted from one generation to the next, and how the information it contains is expressed.
Phenotype - The phenotype of an organism is the observed characteristics of that organism or in the case of bacteria, the observed characteristics of a population of organisms. The phenotype of E. coli is variable depending upon the type of medium used (colonies are pink on MAC, yellow on T-7, and dark with a metalic green sheen on EMB ).
Point mutation - A point mutation is a mutation involving a change in a single nucleotide (base) within a DNA strand or in the RNA of some viruses. Point mutations may be categorized as substitutions, additions, or deletions.
Translocation - A translocation (transposition) is a type of non-point mutation involving the movement of a segment of DNA (one or more genes in length) from one location (locus) to a new location within a chromosome or plasmid, between chromosomes, or between chromosomes and plasmids. These may be caused by transposible elements (transposons) or by crossing over.
Mutagenic agent (mutagen) - A mutagen is a factor (chemical or physical) that increases the mutation rate of nucleic acids. Base analogs, alkylating agents and ultra-violet light are mutagens.
2. Genetics/ DNA or RNA in some viruses
3. locus
4. gene/ split gene
5. genome
6. genotype/ environment
7. genome/ phenotype Note - according to some references, genomic DNA is restricted to the chromosome(s) and does not include plasmid, mitochondrial or chloroplast DNA.
8. phenotype/ environment the organism is exposed to./ The genetic composition of an organism may not be expressed for a variety of reasons. In bacteria, many genes are associated with inducible or repressible operons. If the repressor proteins associated with these operons are active, transcription is blocked and the genetic information cannot be expressed. In diploid organisms certain genes are not expressed because they are recessive. The characteristics they code for are masked by characteristics coded for by dominant genes.
9. mutation Note - This is not a particularly good definition for the term mutation.
10. mutation/ evolution
11. one per 100 million copies of the DNA present/ at least one.
12. substitutions/ The substitution of one base for another within a gene may or may not change the amino acid sequence the gene is coding for because the genetic code is redundant (several different codons code for the same amino acid). A single substitution occurring in the middle part of a gene will influence only one codon, so will potentially change only one amino acid. The addition or deletion of a single base within a gene will result in a frame shift (shift in the codon reading frame) during translation, so will most likely change all of the amino acids being coded for beyond the mutation point. It is unlikely that such a random assortment of amino acids will form a funcional protein, although it is potentially possible.
13. the addition or the deletion of individual bases within/ codons/ ultra violet light
14. translocations (or transpositions)/ transposons (transposable elements)
15. mutagenic agent or mutagen
16. base analogs
17. base analogs/ substitution
18. substitutions/ Ultra violet light
19. Ultra violet (UV) light/deletion
20. transposons or transposable elements/ translocations (transpositions)
21. transposons or transposable elements/ translocations (transpositions)
22. thymine-thymine dimers/ recognizing and breaking the bonds between the thymine molecules thus removing the dimer.
Copyright 2002 Sierra College Biological Sciences Department
Last updated: 02/12/02.
