Inheritance, Selection and Speciation Flashcards
Gene
A sequence of bases on a DNA molecule that codes for a protein which results in a characteristic.
Allele
One or more alternate versions of the same gene (slightly different order of base sequences).
Most plants and animals have two alleles (one maternal and one paternal)
Genotype
Genetic constitution of an organism, i.e. the alleles an organism has.
Phenotype
The expression of the genetic constitution of an organism and it’s interaction with the environment, i.e. an organisms’ characteristics.
Dominant
An allele whose characteristic appears in the phenotype even when there’s only one copy.
Recessive
An allele whose characteristic only appears in the phenotype if two copies are present.
Codominant
Alleles that are both expressed in the phenotype - neither are recessive.
Locus
Plural loci; The fixed position of a gene on a chromosome.
Alleles of a gene are found at the same locus on each chromosome in a pair.
Homozygote
An organism that carries two copies of the same allele.
Heterozygote
An organism that carries two different alleles.
When is inheritance sex-linked?
When the corresponding allele is located on a sex chromosome.
Why are males more likely than females to show recessive phenotypes for sex-linked genes?
Men only have one X-chromosome, thus often have one allele for sex-linked genes, therefore they will express the characteristic of this allele even if it’s recessive.
Examples of X-linked disorders:
Colour blindness, Haemophilia etc…
What hierarchy does the human ABO blood group system work off?
- A and B are codominant
- O is recessive to both.
State the mixed genotypes for the different blood groups:
IAIB = Group AB (only possible genotype) IAIO = Group A IBIO = Group B IOIO = Group O (only possible genotype)
Species
A group of similar organisms that can reproduce to give fertile offspring.
Population
A group of organisms of the same species living in a particular area.
Gene pool
The complete range of alleles present in a population.
Allele frequency
How often an allele occurs in a population.
Usually as a percentage of the total population, or a decimal of thus.
What does the Hardy-Weinberg Principle predict?
That the frequencies of alleles in a population won’t change from one generation to the next.
Under what conditions is the Hardy-Weinberg principle true?
Only if a large population with:
- no immigration
- no emigration
- no mutations
- no natural selection
- random mating
Hardy-Weinberg equation for allele frequency:
p + q = 1
p is the frequency of dominant alleles
q is the frequency of recessive alleles
Hardy-Weinberg equation for genotype frequency:
p^2 + 2pq + q^2 = 1
p^2 is the frequency of the homozygous dominant genotype
2pq is the frequency of the heterozygous genotype
q^2 is the frequency of the homozygous recessive genotype
Explain differential reproductive success:
- Individuals that have an allele that increases their chance of survival are more likely to survive.
- Therefore a greater proportion of the next generation will inherit the beneficial allele.
- They, in turn, are more likely to survive, breed, and pass on their genes.
- Therefore the frequency of the beneficial allele increases from generation to generation.
