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
Some fruit flies have long wings and some have
short wings. Suggest an experiment that could
be used to find out the mode of inheritance for
wing length in fruit flies.
?
do a type of DNA test to find genes/ pedigree to find out if traits are x-linked/hereditary/dom./rec.
Which animals have different blood type variations?
Dogs, cats, horses, and chimpanzees
Co-Dominance
we see a 3rd phenotype of the trait which has both of the other 2 phenotypes present
Four o’clocks are flowering plants. Suggest why
a cross between two lavender four o’clocks
would produce an F1 generation of purple
flowers, lavender flowers, and white flowers.
?
-incomplete dominance: those colours could be an intermediate phenotype
-the flower genes could have multiple alleles for colour
Give an example of how temperature can affect the phenotype of an animal.
-Siamese cat is covered in creamy white fur, except on its ears, face, feet, and tail
-the pattern is due to a mutation in a gene for pigment production
-as a result of the mutation, the enzyme responsible for black fur is sensitive to heat
-the enzyme is active only in the cooler temperatures found at the cat’s extremities, giving the Siamese cat its characteristic appearance
Which blood type is the universal donor?
Type O
Which blood type is the universal acceptor?
Type AB
Can carbohydrates present on the surface of RBC’s be harmful?
yes, if you give someone the wrong blood type since it can cause them to start attacking each other
Which inheritance pattern are roan cattle an example of?
codominance
Which type of dogs are considered universal blood donors for other dogs?
Greyhounds
incomplete dominance
Inheritance pattern in which the phenotype of a heterozygous individual falls in between the two parental phenotypes
-e.g. Snap Dragons and Carnations can be RED (RR), WHITE (rr) or PINK (Rr)
-e.g. People can have STRAIGHT hair (SS), CURLY hair (ss) or WAVY hair (Ss)
incomplete dominance occurs when the phenotype of the heterozygote is an ______ of the parents (snap dragons: red + white = pink)
intermediate
Homoz. dominant and homoz. recessive →intermediate phenotype: heterozygous
codominance
Both alleles are completely expressed at the same time, and so the heterozygous individual has a mixture of two parental phenotypes
-e.g. in cattle, a RED cattle (RR), a WHITE cattle (WW) and a ROAN cattle (RW)
-roan cattle have patches of red hair and white hair intermingled with eachother
multiple alleles
Many genes have more than 2 alleles
E.g. ABO blood type in humans involves 3 alleles (A, B and O)
A person can have 1 of 4 blood types (phenotypes);
A, B, AB, or O
The letters(A,B,O) refer to two types of __________, A and B, that are found on the surface of ________-
carbohydrates; red blood cells
Blood Type A – coated in
carbohydrate A
Blood Type B – coated in
carbohydrate B
Blood Type AB – coated in
both carbohydrate A and B
Blood Type O –
no carbohydrates
blood type O can donate to
everyone
blood type AB can receive blood from
everyone
universal donor
type O
universal acceptor
type AB
IA and IB are _________, and both are also completely dominant over __
co-dominant; i
polygenic trait
range of phenotypes due to additive effects of multiple genes
e.g. eye colour, height, and skin colour in humans
As many as __ genes influence skin colour
60
Different allele combinations account for a great variety in
phenotypes
example of how heredity and environment influence phenotype
E.g. trees genotype DOES NOT change throughout it’s lifetime, however its phenotype DOES change (shape, size, colour, etc.)
greatly depend on the tree’s exposure to sunlight and soil conditions
give an example of how temperature affects phenotype
The Siamese cat pictured is covered in
creamy white fur, except on its ears, face, feet, and tail.
The pattern is due to a mutation in a gene for pigment production.
As a result of the mutation, the enzyme responsible for black fur is sensitive to heat.
The enzyme is active only in the cooler temperatures found at the cat’s extremities, giving the Siamese cat its characteristic appearance.
