Section 7: Genetics, populations, evoloution, and ecosystems Flashcards
Define genotype and phenotype
genotype is the alleles that an organism has
phenotype is the observable characteristics
What is homozygous and heterozygous
Homozygous is when the allele on each chromosomes are the same
Heterozygous is when two alleles are different
What is it called when two alleles both contribute to a phenotype
codominant
What is monohybrid inheritance
the inheritance of a single gene with one trait
What is the difference between monohybrid and dihybrid inheritance
- Monohybrid inheritance:
• Involves the inheritance of one trait controlled by a single gene with two alleles (e.g., flower color).
• Example: Crossing a pea plant with purple flowers (Pp) with one having white flowers (pp).- Dihybrid inheritance:
• Involves the inheritance of two traits controlled by two different genes, each with two alleles (e.g., seed color and seed shape).
• Example: Crossing a plant with yellow round seeds (YyRr) with one having green wrinkled seeds (yyrr).
- Dihybrid inheritance:
What is Mendels law of independent assortment
Each member of the a pair of alleles may combine randomly with either of another pair of
the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.
What are the sex chromosomes of females and males in humans
Females XX chromosomes
Males XY chromosomes
What are non-sex-linked chromosomes called
autosomes
What is autosomal linkage and what does it presume?
When two or more genes are carried on the same autosome
assuming there is no crossing over and don’t segregate.
What is it called when an allele of one gene affects or masks the expression of another in the phenotype
Epistasis
What is epistasis
when an allele of one gene affects or masks the expression of another in the phenotype
If my critical value at p=0.05 is greater than my calculated value of chi-squared is the data significant?
This means there is no significant difference between the observed and expected data. In this case, you accept the null hypothesis and conclude that any differences are likely due to chance.
How do you calculate degrees of freedom
Number of classes minus 1
What are the conditions for the hardy-weinberg principles
no mutations arise
population is isolated
no selection
population is large
mating is random
What are the equations of the hardy weinberg principles
p + q = 1
p2 + q2 + 2pq = 1
Let the probability of allele A = p
and the probability of allele a = q
Define the term allelic frequency
Number of times an allele occurs in a gene pool
State what the hardy-weinberg principle predicts
The proportion of dominant and recessive alleles in a gene pool remains the same from one generation to the next
Genetic variation arises as a result of:
Mutations
Meiosis
Random fertilisation of gametes
State how genetic variation is increases in asexually reproducing organisms
mutation only
State four factors that lead to differential survival and reproduction
predation
competition
disease
natural disasters
What are the three types of selection
stabilising selection - eliminate extremes
directional selection - one extreme favoured
disruptive selection - extremes favoured
What is speciation
the evolution of new species from existing ones
Distinguish allopatric and sympatric speciation
• Allopatric speciation: Occurs when populations are geographically isolated, preventing gene flow and leading to the formation of new species.
• Sympatric speciation: Happens within the same geographic area, often due to reproductive barriers like behavioral differences, polyploidy, or ecological niche specialization.
Explain how isolation can lead to the formation of new species ( 5 marks )
- Populations become isolated (e.g., geographically or reproductively).
- No gene flow occurs between the isolated populations.
- Each population experiences different selection pressures.
- Beneficial mutations arise, and natural selection increases the frequency of advantageous alleles.
- Over time, genetic differences accumulate, and the populations can no longer interbreed to produce fertile offspring, forming new species.