Population Genetics Flashcards
(30 cards)
Population Genetics
the study of genetic variation in populations over time
Population
a local group of individuals of a single species within which mating is actually or potentially
occurring
Gene Pool
set of genetic information carried by all interbreeding members of a population
Gene
general term meaning the physical entity transmitted from parent to offspring during the reproductive process
Genotype
specific allele (or gene) composition of and
individual at specific gene locus
Polymorphism
Gene → can exist in many different forms or states
→ All different forms of a gene are called alleles thus for diploid organisms
Gene Locus → fixed position of the gene on both chromosomes of the chromosome pair (i.e. consists of two alleles )
Polymorphism – two or more variations for a given character
Due to two or more alleles that influence phenotype
* Polymorphic gene – two or more alleles
* Monomorphic – predominantly single allele
Single Nucleotide Polymorphisms (SNPs)
- Smallest type of genetic change in a gene
- Most common – 99% of variation in human gene
sequences - Large, healthy populations exhibit a high level of
genetic diversity - Analysis of SNPs may be important for
personalized medicine – patient’s genotype used
to tailor his or her medical care
Phenotype
the observable characteristics
i.e. the physical traits, or “what you see”
* Observable traits, such as height, eye colour,
and blood type.
* Some traits are largely determined by the
genotype, while other traits are largely determined by environmental factors.
- Codominant:- 3 distinct phenotypes
- Dominant / Recessive:- 2 distinct
phenotypes → heterozygote will have
same phenotype as the dominant
allele homozygote
Genetic Variation
- measure of the genetic differences that exist in a population
Intra-populational variation
- measured as the amount of variation within ecologically and reproductively interacting individuals
- within members of a species in the same area
Inter-populational
- comparing two or more populations of a species
- geographic variation
Genotype Frequency
number of individuals with
that genotype as a proportion of the total number of individuals
Allelic frequency
number of a particular allele as a proportion of the total number of alleles in the population
Allele Frequency
Number of copies of a specific allele in a population / total number of all alleles for that gene in the population
Genotype frequency
number of individuals with a particular genotype in a population / total number of individuals in the population
Hardy-Weinberg Principle
1- Individuals of all genotypes have equal
reproductive success = no selection
2- No new alleles are created or converted into
another by mutation = no mutation
3- Individuals do not migrate into or out of the
population = no migration
4 - Population is infinitely large = no genetic drift
5 - Individuals in the population mate randomly =
random mating
p + q = 1
p2 + 2pq + q2 = 1
Assortive Mating
Occurs when individuals choose their mates based on
their resemblance to each other at a certain locus or a certain phenotype
Positive Assortive Mating
when similar genotypes or phenotypes mate more often than would be expected by chance
Negative Assortive Mating
when like genotypes or phenotypes mate less often
than would be expected by chance
Gene Drift
Change in allelic frequency due to a chance event
Founder effect
The founder effect occurs when a small group of
migrants—not genetically representative of the
population from which they came—establish in a new
area.
Bottleneck event
After a bottleneck, a limited
number of randomly
selected individuals create
a founding population,
resulting in genetic drift
Biological Fitness
Reproductive efficiency of an individual and is expressed in relative terms to other genotypes
Convergent evolution
- Two different species from different lineages show similar characteristics because
they occupy similar environments; species are not closely related evolutionarily
Comparative Anatomy
* Analogous structures – structures which have
converged to provide a similar function, but
are dissimilar in origin e.g. wings of birds and
insects
* Homologous structures – structures that have
diverged due to selective pressures, but share
similarities due to common ancestry e.g. bone
shape, bird beaks
Macroevolution
- evolutionary changes that
produce new species or groups
of species - Large scale changes in the
appearance of a species - Occur very slowly, over many
generations - Fossil records – show differences
in a species over time
Microevolution
- simply a change in gene
frequency within a population. - Evolution at this scale can be
observed over short periods of
time — for example, between one
generation and the next - Canis lupus familiaris is an
example of microevolution as no
new species has resulted.
Evolution occurs on both large and small scales:
