Chapter 8 - Inheritance and Selection Flashcards
What is a phenotype?
The observable characteristics of an organism - result of interaction between expression of genotype and the environment.
What is a gene?
A section of DNA that determines a single characteristic of an organism.
What is an allele?
One of the different forms of a gene.
What is homozygous?
When the allele on each of the chromosomes is the same.
What is heterozygous?
If the two alleles on the chromosomes are different.
What is dominant?
When the allele of the heterozygote expresses itself in the phenotype.
What is recessive?
The allele that does not express itself in the heterozygote.
What is homozygous dominant?
A homozygous organism with two dominant alleles.
What is homozygous recessive?
A homozygous organism with two recessive alleles.
What is co-dominance?
When two alleles both contribute to the phenotype - they are equally dominant.
What is a gene pool?
All the alleles of all the genes of all the individuals in a population at any one time.
What is allelic frequency?
The number of times an allele occurs within the gene pool.
What is directional selection?
When selection favours individuals that vary in one direction from the mean of the population. This changes the characteristics of the population.
What is stabilising selection?
When selection favours average individuals. This preserves the characteristics of a population.
What is speciation?
The evolution of new species from existing species.
What is a species?
A group of individuals that share similar genes and are capable of breeding with one another to produce fertile offspring
What is geographical isolation?
Occurs when a physical barrier prevents two populations from breeding with one another. For example oceans, rivers, mountain ranges and deserts.
What is a genotype?
The genetic constitution of an organism, it describes all the alleles that an organism contains.
What is sex linkage?
A characteristic is sex linked if the gene which controls it is found on one of the sex chromosomes, more commonly the X chromosome because it is longer.
