Patterns of Inheritance Flashcards
Define phenotype
The physical characteristics of an organism
How can meiosis bring about genetic variation
Random assortment of chromosomes
Crossing over of chromatids
Define monogenic inheritance
Where one phenotypic characteristic is controlled by a single gene
Define dihybrid inheritance
Where two phenotypic characteristics are determined by two different genes present on two different chromosomes at the same time
What is meant by sex linkage
Where an allele is located on one of the sex chromosomes
What is meant by multiple alleles
A gene with more than two alleles
What is meant by codominant alleles
two dominant alleles that both contribute to the phenotype
What is meant by autosomal linkage
when two or more genes are located on the same chromosome
Define epistasis
Where two non-linked genes interact with one gene either masking or suppressing the other gene
How can the number of genes coding for a characteristic influence variation
Discontinuous variation = characteristics determined by one gene
Continuous variation = characteristics determined by more than one gene
What is stabilising selection
Occurs when environmental conditions stay the same
Individuals closest to the mean are favoured
results in low diversity
What is directional selection
Occurs when environmental conditions change
Individuals with phenotypes suited will survive and pass on genes
what is genetic drift
A change in a populations allele frequencies that occurs due to chance rather than selective pressure
Define genetic bottleneck
where a catastrophic event dramatically reduces the size of a population
decreasing variety of alleles
What is meant by the founder effect
When a small number of individuals become isolated forming a new population
What is the hardy Weinberg principle
Allows us to estimate the frequency of alleles in a population
what is the Hardy-Weinberg equation for calculating allele frequency
p + q = 1
P = dominant allele
Q = recessive allele
what is the Hardy-Weinberg equation for calculating genotype frequency
p2 + 2pq + q2 = 1
p2 = homozygous dominant
2pq = heterozygous
q2 = homozygous recessive
Define speciation
when the genetic makeup changes to the extent that two groups can no longer interbreed
Define allopatric speciation
speciation resulting from a physical barrier
What is sympatric speciation
Speciation resulting from non-physical barrier
What is artificial selection
Humans choose particular organisms to breed together
Give examples of artificial selection in plants and animals
Plants = seedless fruits, higher yield
Animals = cows with higher milk yield
Examples of ethical issues of the use of artificial breeding
Anatomical changes in animals
Higher susceptibility to disease
