What are meant by the terms gene pool and allelic frequency?
What is the Hardy-Weinberg equillibrium,(or equation)
Tuesday 10 December 2013
Sunday 8 December 2013
Multiple Alleles
Multiple Alleles
In Mendel's studies, he proposed that there are two alleles for every gene, the dominant of the two having its phenotype expressed in a heterozygote. However, a gene can have more than two allelic forms segregating within a population.
These genes are referred to as having multiple alleles. This does not mean that the gene in a particular individual possesses more than two alleles. An individual can only have a maximum of two of the alleles, one maternal and one paternal, no matter how many alleles exist in the population.
An example of multiple alleles of a gene is the C series in dogs.
C is required for color while cc yields an albino. The genotypes and phenotypes are as follows:
C is a dog with color series expressed
cch is a chinchilla patterned dog
cd is a white dog with dark eyes
cb is a pale gray dog
c is an albino dog (pale eyes and nose)
You can click on all of the genotypes in this animation to see what these dogs look like.
The series works in such a way that C>cch>cd>cb>c. When an allelic series is written like this, it means that the allele to the left, in this case the C allele, is dominant to every allele to its right, while the next allele (cch) is dominant to everything but the allele to its left (C), and so on. In this system, the c allele is recessive to all of the other alleles.
http://www.ansci.cornell.edu/usdagen/mult_alleles.html
Assignment
1) Research the Allelic control of Blood groups on the internet.
2) Why is the control of blood groups a good example of multiple alleles?
3) Explain, with examples of pedigrees, another example of multiple alleles.
4) Explain with examples, Co-dominance.
Post these up to me as answers on the blog. if you don't want to type, get someone in IT to scan it into the computer for you.
Keep in touch.
Bn.
In Mendel's studies, he proposed that there are two alleles for every gene, the dominant of the two having its phenotype expressed in a heterozygote. However, a gene can have more than two allelic forms segregating within a population.
These genes are referred to as having multiple alleles. This does not mean that the gene in a particular individual possesses more than two alleles. An individual can only have a maximum of two of the alleles, one maternal and one paternal, no matter how many alleles exist in the population.
An example of multiple alleles of a gene is the C series in dogs.
C is required for color while cc yields an albino. The genotypes and phenotypes are as follows:
C is a dog with color series expressed
cch is a chinchilla patterned dog
cd is a white dog with dark eyes
cb is a pale gray dog
c is an albino dog (pale eyes and nose)
You can click on all of the genotypes in this animation to see what these dogs look like.
The series works in such a way that C>cch>cd>cb>c. When an allelic series is written like this, it means that the allele to the left, in this case the C allele, is dominant to every allele to its right, while the next allele (cch) is dominant to everything but the allele to its left (C), and so on. In this system, the c allele is recessive to all of the other alleles.
http://www.ansci.cornell.edu/usdagen/mult_alleles.html
Assignment
1) Research the Allelic control of Blood groups on the internet.
2) Why is the control of blood groups a good example of multiple alleles?
3) Explain, with examples of pedigrees, another example of multiple alleles.
4) Explain with examples, Co-dominance.
Post these up to me as answers on the blog. if you don't want to type, get someone in IT to scan it into the computer for you.
Keep in touch.
Bn.
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