Cellular Control and Patterns of Inheritance Key Terms and Processes Flashcards
Define the term :
Genotype
Alleles for a particular characteristic present in the cells of an organism
Define the term :
Phenotype
Observed characteristic of an organism
Define the term :
Homozygous
Organism with two identical alleles for a particular gene
Define the term :
Heterozygous
Organism with two different alleles for a particular gene
Define the term :
Dominant
Characteristic that is always expressed in the phenotype in an organism, even in those who are heterozygous
Define the term :
Recessive
Characteristic only expressed in the phenotype when there is no dominant allele present
Define the term :
Co-Dominant
A characteristic where both alleles contribute to the phenotype
Define the term :
Linkage
2 or more genes located on the same chromosomes and are normally inherited together
Define the term :
Sex Linkage
Genes with a locus on one of the sex chromosomes (X or Y). Most are on the X chromosome
Define the term :
Epistasis
Interaction of genes concerned with the expression of one characteristic, one allele may mask or suppress the expression of another allele
Define the term :
Discontinuous Variation
No intermediate categories, phenotypic variation is clearly distinguishable categories, eg; blood group, attached ear lobes, etc
Define the term :
Continuous Variation
Phenotypic differences with a wide range of variation with no distinct categories, eg; height weight, etc
Define the term :
Allele
Alternative form of a gene found in a specific locus on a specific chromosome
Define the term :
Pure Breeding
Homozygous at both alleles, can both be dominant or recessive
Define the term :
Multiple Alleles
Characteristic for which there are three or more alleles
Define the term :
Dihybrid
Involving two gene loci
Define the term :
Monogenic
Determined by a single gene
Define the term :
Polygenic
Determined by multiple genes
Define the term :
Mutation
A sudden, significant, random change in the sequence of nucleotides in DNA during DNA replication.
Define the term :
Mutant
An organism affected by (a) mutations
Define the term :
Somatic Mutation
Mutations in non-reproductive cells which cannot be inherited by offspring
Define the term :
Germ-Line Mutation
Mutation in gametes, can be inherited by offspring
Define the term :
Mutagens
Things like radiation or chemicals (eg in cigarette smoke) that increase the chance of mutations occurring
What is a regulatory gene?
- a gene that is present in DNA
- it has a role in the regulating the expression of structural genes
Define the term :
Point mutation
A mutation where one base pair is changed
Missense mutation
The first base pair of a triplet codon mutates (likely amino acid change)
Silent mutation
Mutation that occurs on the second/third base (unlikely amino acid change)
Point, Missense and Silent mutations are all types of _________ mutations
Substitution
Insertion and deletion is a type of _________ mutation
Frameshift
What are neutral mutations?
Mutations that have no effect on the survival of the organism
Define the term:
Reproductive Isolation
When two populations of the same species change sufficiently, they fail to interbreed successfully and are said to be reproductively isolated, they have become two separate species, which are genetically isolated
Define the term:
Prezygotic
Zygotes do not form because the gametes do not meet
Define the term:
Post Zygotic
Zygotes are formed, but they do not produce mature fertile offspring
Reasons for Pre-zygotic Isolation Mechanisms
• Geographical Isolation
The populations never meet because they inhabit different areas
• Ecological Isolation
The populations never meet because all though they inhabit the same area, they live in the habitats within that area
• Temporal Isolation
The populations never meet although they inhabit the same area, they love in different habitats within that area
Deletion
When part of a chromosome containing genes and regulatory sequences is lost
Inversion
When a section of a chromosome may break off, turn through 180° and then rejoin, this results in genes being present but not be too far away from their regulatory sequence to be properly expressed in the phenotype
Translocation
A piece of chromosome beams off and attaches to different chromosomes, this can interfere with the regulation of genes on the chromosome with the new DNA
Duplication
A piece of chromosome may be copied, this can lead to over expression of genes which can be harmful, as TOL many proteins are produced which can affect the metabolism
Non Disjunction
When a pair of chromosomes or chromatids fail to separate in meiosis are lying in a gamete with an extra chromosome, when the gamete is fertilised, the zygote has an extra chromosome
eg - Down syndrome, when individuals have three copies of chromosome 21
Define the term:
Operon
A sequence of DNA containing a cluster of genes under the control of a single promoter
