Patterns of inheritance and Variation Flashcards
What are the types of variation?
continuous and discontinuous
What are levels at which variation can be influenced?
genes, environment and both
How is there variation at a genetic level?
crossing over in prophase 1, independant assortment of chromosomes in metaphase 1, independant assortment of chromatids in metaphase 2, random fusion of gametes, mutations
How is continuous and discontinuous variation controlled?
continuous - many genes
discontinuous - one gene
How does both genetic and environmental factors influence phenotype?
genetic factors determine genotype and the characteristics they are born with but then environmental factors influence how they develop
What are the two types of alleles?
dominant and recessive
What is codominance?
two different alleles occur for a gene and both are expressed in the phenotype as they are equally dominant
What is a dihybrid cross?
inheritance of two different characteristics (YyRr)
What is autosomal linkage?
genes on same chromosome are inherited together
What is a recombinant offspring?
an offspring that has a different combination of alleles than either parent
When is null hypothesis rejected in Chi squared test and what can you conclude from that?
if chi squared value is greater than critical value at p=0.05 then there is a sig. difference between expected and observed
What is an epistatic gene?
a gene that masks the expression of another gene
What is recessive and dominant epistasis?
recessive - presence of two recessive alleles masks the expression of another gene
dominant - presence of one allele masks another gene
What is an example of epistasis?
in labradors one gene codes for whether pigment is deposited in skin or skin and fur. Another gene codes for the colour of pigment produced. The first gene is epistatic as if they have two recessive alleles then pigment is only deposited in skin and so pigment of fur will not be shown as there is no pigment deposited there so the second gene is masked
What does the hardy wienburg principle assume?
population is large, random mating occurs (also that no immigration, emigration, mutations or natural selection occurs)
What are the factors affecting rate of evolution?
mutation, sexual selection, gene flow, genetic drift, natural selection
What is the impact of small populations?
small genetic diversity so little variation, population cannot easily adapt to changes in environment so more chance of becoming extinct
What are the two types of limiting factors for a population?
density dependant and density independent
What are some example of density dependant and independent factors affecting population?
dependant - competition, prey, predation, disease
independent - climate change, natural disasters, seasonal change, human activity
What is the founder effect?
small population arises due to isolation, gene pool is tiny and very low genetic diversity, only the few alleles in new colony can be passed on to offspring
Describe the process of natural selection?
there is variation within a population due to random mutation, a selection pressure creates a struggle for survival, some individuals are better adapted to the selection pressure due to variation, these individuals survive and can reproduce, a greater proportion of next generation have this advantageous allele, they are then more likely to survive and reproduce and over many generations this allele becomes more frequent in gene pool
What is stabilising selection?
the norm is selected for and extremes are selected against
What is directional selection?
most common phenotype is no longer advantageous and one extreme is selected for
What is disruptive selection?
both extremes are selected for and norm is selected against
What must happen in order for speciation?
members of population become isolated and no gene flow occurs. random mutation continues in both groups. Selection pressures differ for the groups. changes in allele frequency in both groups is different and after many generations the groups become reproductively isolated
What is allopatric speciation?
members of population become separated by a physical barrier and condition for each populations vary and then so do selection pressures
When does reproductive isolation occur?
different mating seasons developed, changes in genitalia, new courtship rituals different from main population
What is the process of artificial selection?
individuals are selectively bred due to desirable characteristics, so the these alleles are ‘selected for’, same as natural selection but selection pressure is humans choosing desirable characteristics
What are some issues with artificial selection?
small gene pool, helpful alleles could be lost, exaggerates certain traits, increased chance of disease, ethical issues
