genetics of living systems Flashcards
1
Q
what is a gene pool
A
- sum total of all the genes in a population at any given time
2
Q
what is allele frequency
A
- relative frequency of a particular allele in a population
3
Q
how do you calculate allele frequency?
A
p+q= 1
4
Q
what is the hardy-wienberg principle-
A
- models the mathematical relationship between the frequencies of alleles and genotypes in a theoretical population
5
Q
what is the hardy-wienberg principle formula
A
- p^2 + 2pq + q^2 = 1
where p^2= frequency of homozygous dominant
where 2pq = frequency of heterogygous
where q^2 = frequency of homozygous recessive
frequency of the recessive allele = square root of q^2
6
Q
what are the factors affecting evolution?
A
- mutations
- genetic drift
- gene flow
- natural selection
- sexual selection
7
Q
explain how mutation affects evolution?
A
- a mutation will cause a random change in the DNA base sequence and formation of new allele leading to genetic variation
8
Q
explain how sexual selection affects evolution
A
- leads to an increase in frequency of alleles in which they code for characteristics that improve mating success
9
Q
explain how gene flow affects evolution
A
- movement of alleles between populations, immigration and emigration result changes of allele frequency within a population
10
Q
explain how genetic drift affects evolution?
A
- occurs in small population. this is a change in alleles frequency due to mutation.
- appearance of new allele will have a greater impact in a smaller population than in much larger where there is a great number of alleles present in the gene pool
11
Q
explain how natural selection affects evolution?
A
- leads to a increase in the number of individuals that have characteristics that improve their chances of survival
- reproduction rates of these individuals will increase as will the frequency of the alleles coding for the characteristics
12
Q
what factors lead to speciation?
A
- members of the population become isolated and no longer interbreed with the rest resulting in no gene flow between the two groups
- alleles within the groups continue to undergo random mutations. the environment of each group may be different or change so different characteristics will be selected for and against
- accumulation of mutations and changes in allele frequencies over many generation eventually lead to large changes in phenotype
13
Q
what is allopatric speciation
A
- when some members of a population are separated from the rest of the group by a physical barrier such as a river or the sea- geographically isolated
- the environment of different groups will often be different so will the selection pressures resulting in different physical adaptations.
it can also lead to genetic drift further enhancing the differences between the populations
14
Q
what is sympatric speciation
A
- occurs within populations that share the same habitat
- happens less frequently than allopatric speciation and is more common in plants than animals
- occurs when members of two different species interbreed and form fertile offspring this often happens in plants. the hybrid formed which is a new species will have a different number of chromosomes to either parent and may no longer be able to interbreed with members of either parent populations this stops gene flow and reproductively isolates hybrid organism
15
Q
what are reproductive barriers
A
- barriers to successfull interbreeding can form within populations before or after fertilisation has occurred
- prezygotic reproductive barriers prevent fertilisation and the formation of a zygote. postygotic reproductive barriers often produce as a result of hybridisation reduce the viability or reproductive potential offspring
