Inheritance, Selection And Speciation Flashcards
What is an allele?
An allele is a version of a gene. Alleles code for different versions of the same characteristic, e.g. Allele for blue eye or allele for brown eye.
What is a genotype?
A genotype is the genetic constitution of an organism, e.g. Bb for eye colour.
What is a phenotype?
The expression of the genetic constitution, e.g. Brown eyes.
What is a dominant allele?
A dominant allele is a allele whose characteristic appears in the phenotype when there is only one copy of the allele. E.g. Bb will make brown eyes with only one dominant allele.
What is a recessive allele?
A recessive allele is an allele which you need 2 copies of to have the phenotype. E.g. bb will make blue eyes because there are 2 recessive alleles.
What is co dominance?
Co dominant alleles are alleles which are both expressed in a phenotype.
What is a homozygote?
An organism which carries 2 copies of the same allele, e.g. BB or bb.
What is a heterozygote?
An organism which carries 2 different alleles, e.g. Bb.
What is a sex linked gene?
A sex linked gene is when the allele which codes for that gene is found on a sex chromosome.
Why are males for likely to show recessive phenotypes of sex linked genes?
The Y chromosome is smaller than the C chromosome and it carries fewer genes. So most genes on the sex chromosomes are found on the X chromosome. Males only have one X chromosome so they only have one allele for the sex linked gene. Therefore the always express the characteristic of this allele, even if it is recessive.
What is allele frequency?
Allele frequency is how often an allele occurs in a population.
What does the Hardy-Weinberg principe predict?
The Hardy-Weinberg principle predicts that the frequency of alleles won’t change from one generation to the next.
What are the conditions for the Hardy-Weinberg principle?
There must be a large population where there is no immigration, emigration, mutations or natural selection. Also, there needs to be random mating (all possible genotypes can breed with others).
What are the equations for the Hardy-Weinberg equation?
p+q=1
p2 +q2 +2pq = 1
How can the allele frequency be changed from one generation to the next?
If an allele increases the chances of an organism surviving, individuals with this advantageous allele will be more likely to survive and reproduce and pass their genes on. Therefore there offspring will have the advantageous allele. A greater proportion of the next generation will have the advantageous allele. So the frequency of it increases from generation to generation.
