Probability
What is Probability?
It is the likelihood that a particular event will happen.
What is a homozygous?
an organism has two identical alleles of a gene
What is independent assortment?
one of Mendel’s principles that states that genes for different traits can segregate independently during the formation of gametes
What is the probability that ca coin flip will land heads up?
1/2 or 50%
What is a heterozygous?
an organism has two different alleles for the same gene
What is codominance?
If alleles have codominance, the phenotypes made by both alleles show up at the same time. For example, in certain kinds of chickens, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens are speckled with black and white feathers. Because of codominant alleles, the black and white colors both appear.
If you flip a coin three times in a row, what is the probability that it will land heads up every time?
1/2 x 1/2 x 1/2 = 1/8
What is a phenotype?
the physical characteristics of an organism
What is incomplete dominance?
Cases where one allele is not completely dominant are called incomplete dominance. In incomplete dominance, the heterozygous phenotype lies somewhere between the two homozygous phenotypes. Four o’ clock plants are an example of this. A cross between red-flowered (RR) and white-flowered (WW) plants results in offspring with pink flowers (RW).
Since a pea plant has two alleles for every gene, the probability that a gamete will get either allele is 1/2. If two pea plants that have one of each kind of allele (Tt) are crossed, what is the probability that an offspring plant will be short? Remember that to be short, a plant needs two t alleles.
1/2 x 1/2 = 1/4
What is a genotype?
the genetic makeup of an organism
What is multiple alleles?
a gene that has more than two alleles. One of the best examples of multiple alleles is coat color in rabbits. A rabbit’s coat color is controlled by one gene that has four possible alleles. The four known alleles display a pattern of simple dominance that can produce four coat colors.
Since a pea plant has two alleles for every gene, the probability that a gamete will get either allele is 1/2. If two pea plants that have one of each kind of allele (Tt) are crossed, what is the probability that an offspring plant will be tall? Remember that to be short, a plant needs two t alleles.
1/2 x 1/2 + 1/2 x 1/2 + 1/2 x 1/2 = 3/4
What does the prefix hetero- mean?
"different" The two alleles in a heterozygous organism are different from one another.
What are polygenic traits?
a trait controlled by two or more genes. For example, at least three genes are involved in making the reddish-brown pigment in the eyes of fruit flies.