Chapter 9 Flashcards
Gene Pool
The complete set of alleles present within a particular population.
Gene
Section of DNA that carries the code to make a protein.
Allele
Alternate form of a gene.
Population
Group of individuals of the same species living in the same location.
Allele frequency
Proportion of certain alleles in a gene pool.
Larger and more diverse allele pool =
- Greater gene variety + alleles.
- Therefore a greater number of genotypes and phenotypes.
- Increasing genetic diversity.
Genotype
Genetic compostion of an organism at a particular gene locus.
Phenotype
An organism’s Physical or biomedical characteristics result from gene expression and the environment.
Genetic diversity.
Variation in genetic makeup or alleles within a population.
Mutations
Permanent change to a DNA sequence.
- Introduce new alleles into a population via changes to DNA.
- Spontaneous or Induced by Mutagens.
- Can be advantageous, neutral or deleterious.
Mutagens
An agent that can cause mutations in DNA.
Mutations cause:
Effect downstream expression of a particular gene, altering the folding and functioning of the resultant protein.
For mutations to be inheritable
Needs to occur in germline cells.
If occurs in somatic cells –> Non-inheritable.
Heritability
Transmission from parent to offspring
Germline cells
Cells involved in the generation of gametes in eukaryotes.
Somatic cells
Any cell in an organism that isn’t a germline cell.
Point mutations
Mutations that alter a single nucleotide in a DNA sequence.
- Silent mutations.
- Missense mutation.
- Nonsense mutation.
- Frameshift mutation.
Silent Mutation
Substitution mutation that has no effect on resulting amino acid. A nucleotide is substituted for another, changing the codon, still coding for the same amino acid. (no effect on protein).
Substitution of a single nucleotide which does not lead to a change in the amino acid sequence
Missense Mutation
Substitution mutation which codes for a different amino acid altering the primary structure of the polypeptide. (alters the function of proteins).
Substitution of a single nucleotide which changes the affected codon, leading to the production of a different amino acid
Nonsense mutation
Prematurely end translation of genes mRNA. Substitution of nucleotide –> causes the affected codon to become a STOP codon. Therefore polypeptide becomes too short; the gene isn’t completely translated.
Substitution of a single nucleotide leading to the production of a premature stop codon
Frameshift mutation
Addition/deletion of 1 or 2 nucleotides that alter the reading frame of nucleotides. All following codons and amino acids they code for are affected causing major disruptions to the structure/function of a protein.
Insertion or deletion of nucleotides affecting every codon from the point of mutation onwards
Sickle cell anaemia
Genetic disease (due to missense mutation) that leads to the formation of new allele causing deformity in red blood cells.
Normal red blood cells appearance
Flatten disk-like; transports oxygen.
Sickle cells appearance
- Shaped like crescents(increased length + width).
- Unable to carry oxygen efficiently.
Block mutations
Mutations that affect large amounts of DNA or entire genes
Changes to large sections of DNA causing significant changes to DNA sequences.
- Duplications;
- Deletions;
- Inversions;
- Translocations;
