5.2 Extending Mendel's Laws Flashcards
Define “complete dominance” for a genetic trait.
-one allele is expressed and the other is not
e.g. In Mendel’s pea plant crosses, the F1
heterozygous offspring always resembled the
homozygous dominant parent. For each trait, one
dominant allele was expressed.
Codominance Example
-In cattle, a cross between a true-breeding red
bull and a white cow will produce roan calves.
-Roan cattle have patches of white hair intermingled with patches of coloured hair
-This mixed phenotype results from the expression of the white-hair allele in some patches, and the coloured-hair allele in other patches
Incomplete Dominance Example
-heterozygous individuals have an in-between phenotype
-e.g. alleles controlling feather colour in Andalusian chickens are neither dominant nor recessive.
Polygenic Inheritance Example
In humans, eye colour, skin colour, and height
exhibit polygenic inheritance
Codominance
In the case of codominance, both alleles are completely expressed at the same time, and so a heterozygous individual has a mixture of the two parental phenotypes.
Incomplete Dominance
inheritance pattern in which the phenotype of a heterozygous individual falls between the two parental phenotypes
Multiple Alleles
the existence of multiple alleles means that there may be many possible genotypes for a particular gene, and many possible phenotypes
Polygenic Traits
range of phenotypes due to the additive effects
of multiple genes
What form of inheritance does ABO blood type
in humans exhibit?
codominance (both alleles expressed same time)
-genes with multiple alleles
What is the difference between incomplete dominance and codominance?
I.D= intermediate (“in-between”) phenotype
CD= both alleles expressed at same time
How many genotypes exist for human ABO blood type?
six possible genotypes
What blood types can be donated to a person with blood type B?
type O and type B
Give an example of a human trait
influenced by the environment
blood-cell counts and cholesterol levels, are sensitive to environmental influences
Blood count depends on factors such as the presence of an infection, a person’s level of physical activity,
and the altitude at which the person lives.
Diet and lifestyle, as well as genetics, influence cholesterol levels.
Give an example of a human PHYSICAL trait
influenced by the environment
weight, height, size, and colour.
If a child does not get proper nutrition, their height may be stunted as an adult.
Without the right vitamins and nutrients, they may not reach their inherited potential due to environmental influences.
If two parents have blood type O, what are the
possible ABO blood types of their children?
type O
What is the form of inheritance in which a
heterozygous individual has a phenotype
that is in between the parental phenotypes?
incomplete dominance
Which type of gene refers to parents who
are heterozygous for a codominant trait and can have
offspring that show one of three phenotypes
blood types (genes with multiple alleles)
Give the phenotypes of the F1 generation from
a cross between a white snapdragon and a
pink snapdragon
100% light pink (Ww)
The hydrangeas in the following photo all have
the same genetic makeup. Explain why the
plants have different phenotypes.
Environmental influence
-flower colour can be influenced by the nutrients and pH of the soil
-hydrangeas grown in slightly acidic soil have blue flowers, but if grown in slightly basic soil have pink flowers