How Species Evolve Flashcards
Define Gene pool.
Refers to the total aggregation of all the genes and alleles present within a particualr population of species.
Define Allele frequencies.
Refers to the proportion of a particular allele appearing at a certain gene locus in a gene pool.
Give an example of allele frequency.
If there were two alleles of the gene coding for the colour of sheep (B and b), their frequencies could be calculated by totalling the number of a particular allele divided by the total number of alleles present in the population.
Define Alleles.
An alternate form of a gene. For example, the gene is for eyes the different alleles are the different colours.
A large and more diverse gene pool will contain a variety of [a] _ and [b]_ , leading to a greater number of [c] ___and [d] ____ , and thereby resulting in increased [e]___ .
A. Genes
B. Alleles
C. Genotypes
D. Phenotypes
E. Genetic Diversity
Define Genetic Diversity.
The variation in genetic makeup or alleles within a population.
Define Mutations.
Mutations involve permanent changes to the DNA sequence of an individual and can occur either spontaneously or be induced by agents known as mutagens (e.g. UV radiation).
What happens when a mutation occurs in the DNA sequence of genes?
They can have a significant downstream effect on the expression of that particular gene by altering the folding and functionality of the resultant protein.
The mutations can be classified as advantageous, neutral or delecterious depending on…
Depending on the mutation’s overall effect on the survivability of the individual affected.
When can a mutation be classified as deleterious, advantageous and neutral?
Deleterious: if the mutation leads to the production of an abnormally functioning protein
Advantageous: if it led to the production of a protein which enhances the survivability of an individual.
Neutral: Normally functioning protein, it doesnt affect the functioning.
How does mutations increase genetic diversity and therefore what is its evolutionary significance?
Due to their ability to create and introduce new alleles into a population,
What are the two categories of mutations?
Mutations can be categorised as either point mutations or block mutations, depending on whether **they affect a single nucleotide base or a larger cluster of nucleotides. **
What are the subgroups of point mutations?
Silent mutation: Substitution mutations that have no effect on the resulting amino acid sequence. Due to the degenerate nature of the genetic code, multiple different codons cde for the same amino acid, and therefore despite a change to the original DNA sequence, the same amino acid is incoporated into the protein.
**Missense mutation: **Substitution mutations which code for a different amino acid, altertering the primary structure of the polypeptife. This in turn affects the folding of the polypeptide and could alter the functioning of the protein.
**Nonsense mutation: **Sub mutations which prematurely end the translation of a gene’s mRNA. Due to the substitution of a nucleotide that causes the affected codon to become a stop codon, the gene will not be completely translated, leading to a polupeptide that is too short to function as intended. These mutations are generally the most DANGEROUS.
Frameshift mutation: Addition or deletion of one or two nuleotides, which alter the reading frame of all the following nucleotides.
The reading frame is how DNA or mRINA is divided into triplets or codons respectively. Since the reading frame is shifted in frameshife mutations, all following codons and the amino acids they code for are affected, which can cause major disruptions to the structure and function of the proteins.
What are the alterations of the structure of a chromosome, in block mutations?
Deletion: Removal of a section of DNA.
Duplication: Replication of a section of DNA, lengthening the DNA.
Inversion: Reversal of a section of DNA.
Translocation: Switiching of two sections of DNA on different chromosomes.
When does Block mutation usually occur?
During the procsess of meiosis.
Define Environmental selection pressures.
Factors within the environment that influence the survivability of a species within a given environmement.
What are some examples of environmental selection pressures and what process can occur due to these factors?
Predation, disease, competition, and climate change. Through these factors, the process of natural selection can occur.
Define Natural selection.
Involves the selection of the phenotype most suited to overcome the environmental selection pressure.
