variation in our existence
DESCRIPTION
Variation In Our Existence. Variation=Biodiversity. Variation within a species can be attributed to many thing: Mutations in genes Independent assortment of homologous chromosomes during meiosis 1 Independent assortment of sister chromatids during meiosis 2 - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/1.jpg)
![Page 2: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/2.jpg)
Variation within a species can be attributed to many thing: Mutations in genes Independent assortment of homologous
chromosomes during meiosis 1 Independent assortment of sister chromatids
during meiosis 2 The crossing over of homologous
chromosomes during meiosis
![Page 3: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/3.jpg)
A gene pool refers to all of the genes that occur in a population
The frequency of some genes stays consistent over generations. Some frequencies change very rapidly, especially if they are maladaptive to survival or reproduction.
![Page 4: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/4.jpg)
Certain gene frequencies are associated with certain populations.
![Page 5: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/5.jpg)
Smooth peas are either AAor Aa Wrinkled peas are aa
Population biologists and geneticists like to know what the frequency of these alleles are.
A may occur in AA or Aa. Perhaps the A allele has a frequency of 0.78 in a population
a may only occur in aa. Its frequency in the population is 1-0.78=0.22
![Page 6: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/6.jpg)
Many traits have two forms: dominant allele and recessive allele. (ie. Smooth or wrinkled pea)
We call the dominant allele “p”
We call the recessive allele “q”
So “A” becomes “p” and “a” becomes “q” when talking about alleles.
![Page 7: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/7.jpg)
p=frequency of allele “A"q=frequency of allele “a“
p + q= 1
![Page 8: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/8.jpg)
p2 + 2pq + q2= 1
AA + Aa + aa=1
(these are genotype frequencies, not allele frequencies!)
![Page 9: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/9.jpg)
If all other factors remain constant, the gene pool will reach genetic equilibrium (the gene pool will be the same generation after generation).
No evolution occurs, unless something disrupts the equilibrium.
![Page 10: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/10.jpg)
The conditions under which NO CHANGE will occur in a gene pool are: Large population Random mating No mutations of
genes No migration (no
new genes entering!) Equal fertility and
mating ability of all genotypes
![Page 11: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/11.jpg)
p + q = 1p2 + 2pq + q2= 1
AA Aa aa
If the values of p and q are known, you can calculate the freuqncy of the three genotypes “AA” “Aa” “aa”
If the frequencies of the three genotypes are known, you can calculate the frequency of the alleles “p” and “q”
![Page 12: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/12.jpg)
What are the allele frequencies of F and f in the population?
What percent of the population are homozygous dominant, heterozygous, and homozygous recessive for trait “F”?
![Page 13: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/13.jpg)
Suppose a recessive genetic disorder occurs in 9% of the population. How many of the population carry the recessive gene but do not have the disorder (How many are heterozygous??)
![Page 14: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/14.jpg)
Since the disease only occurs in homozygous recessive individuals, the frequency of the aa genotype is 0.09.
p2 + 2pq + q2= 1
q2=aaq2=0.09√0.09=0.3 therefore, frequency of a is 0.31-0.3=0.7 therefore, frequency of A is 0.7
0.72 + 2(0.7)(0.3)+ .32= 10.49 + 0.42 + 0.09=1 42% are
heterozygous
![Page 15: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/15.jpg)
Page 192, #1-8
http://More Questions and Answers for Practice
http://Awesome Video to Help
![Page 16: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/16.jpg)
Disturbs equilibrium Allele frequencies in a population change
randomly over time due to chance This will occur more in smaller
populations, because 1 change will effect most of the population
![Page 17: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/17.jpg)
Also known as immigration or emigration
Movement in or out of a population will change the gene pool.
![Page 18: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/18.jpg)
New species must arise from existing species
Two ways in which a new species can arise are: Geographic isolation Reproductive isoloation
Populations become isolated and must adapt to their new environment.
![Page 19: Variation In Our Existence](https://reader034.vdocuments.us/reader034/viewer/2022051401/56814bbb550346895db88eaa/html5/thumbnails/19.jpg)