Genetic Variation/Diversity Flashcards
What does random fusion of gametes allow for
This random fusion of gametes at fertilization creates genetic variation between zygotes as each will have a unique combination of alleles
During fertilization can any male gamete fuse with any female gamete to form a zygote
Yes - means fusion of gametes is random
How does independent assortment increase genetic variation
The different combinations of chromosomes in daughter cells increases genetic variation between gametes
Why is swapping of alleles important in crossing over
it can result in a new combination of alleles on the two chromosomes
What is the number of possible chromosomal combinations resulting from meiosis equal to
2 to the power of n (n is the number of homologous chromosome pairs / haploid number)
What would the calculation and answer be for the number of possible chromosomal combinations in a humans
2^23 = 8 388 608 possible chromosomal combinations
What is the formula to calculate the number of combinations of chromosomes after the random fertilisation of two gametes
(2^n)^2 (N is haploid number and ^2 is the number of gametes.
What would the formula be for the number of combinations following fertilisation in humans
(2^23)^2 = 70,368,744,177,664
Why is there so much genetic variation in meiosis
2^23 is just the number of different possible gametes that one human can make. As sexual reproduction involves the random fusion of two gametes, potentially any one of the > 8 million possible combinations that a male can make following meiosis can fertilise any one of the > 8 million possible combinations that a female could make.
What is genetic variation
The small differences in DNA base sequences between individual organisms within a species
What does genetic variation through generations result in
Genetic Diversity
What is genetic diversity
The number of different alleles of genes in a population
What does mutation result in
The generation of new alleles and contributes to genetic diversity or the size of the gene pool
What effect does the genetic code being degenerate have on the effectiveness of an allele
The new allele may be advantageous, disadvantageous or have no apparent effect on phenotype.
Are new alleles always presented
No, they can remain hidden (not expressed) within a population for generations
Why is genetic diversity important for the development of a species
It allows for natural selection to occur, resulting in differences in phenotype.
What are selection pressures and what do they do
Environmental factors that increase the chance of individuals with a specific phenotype surviving and reproducing over others (these organisms have a higher fitness)
What is meant by the fitness of an organism
It’s ability to survive and pass on it’s alleles to offspring
What are the characteristics of large gene pools
Large gene pools have a strong ability to adapt to change
What are the characteristics of small gene pools
Small gene pools have lower genetic diversity = bottle necks = vulnerable to extinction
What are the effects of genetic diversity
Natural selection, differences in phenotype, selection pressure, increase the chance of a specific phenotype
What is a bottleneck event
An event which causes a large reduction in populations (e.g. organisms die before they reproduce)
What occurs after a bottleneck event
Survivors reproduce and a larger population is created using fewer genes
What is the founder effect
When a reduced number of organisms from a population start a colony and the founder population only takes a reduced number of alleles in the initial population
What is the only way the founder effect can occur
From a migration / separation from the original population
What are the negative effects of the founder effect
Frequency of alleles is likely to be different in the new colony and could lead to genetic diseases being bred in or out of populations
how can genetic diversity be investigated
By comparing the frequency of measurable or observable characteristics
