Notes ALL
Name
  More About Genetics  
Date
1.
pd.
You are an organism with 2 copies of a gene. When your gametes undergo cell division, or
the 2 copies of each gene would need to separate. This is called
, the process of
separating 2 alleles of a gene.
2.
Therefore, if you have the genotype Ee for long eyelashes, half your gametes will carry the allele for long
eyelashes and the other half will carry the allele for
3.
Do the genes of your eye color have any influence on the genes of your hair color? NO! Alleles segregate
independently from one another. This principle is known has
4.
So what was learned from Mendel’s experiment? Today, biologists look back on Mendel’s work and noted 4
important principles that he developed.
1. Individual units called ___________________________ determine biological characteristics
2. For each gene, an organism receives one allele from each parent. The alleles separate from each other – a
process called________________________________ – when reproductive cells are formed.
3. If an organism inherits different alleles for the same trait, one allele may be _____________________ over
the other.
4. __________________ segregate independently.
A complex organism may have thousands or even tens of thousands of genes. Many genes have more than one allele or
have alleles that are neither dominant nor recessive. Take for example the flower snapdragons. It has 2 alleles for
flower color (R, red & r, white).
a. Snapdragons that are homozygous red
white
produce red flowers. Those that are homozygous
produce white flowers. Those that are heterozygous
produce pink!
b. In this case neither allele is completely dominant. The red in the snapdragon displays
The heterozygous phenotype is somewhere in between the two homozygous phenotype.
5.
When both alleles of a gene is expressed, this is called
6.
In certain types of chickens, there are 2 codominant alleles for feathers. One black and one white. Therefore if
the chicken’s genotype is heterozygous, the feathers of the chicken will be
7.
Many inherited traits are controlled by more than one gene. For example, your facial appearance. It is inherited
but no single gene determines the exact shape of your mouth or the position of your ears. Traits that are
controlled by more than one gene are said to be
Complete dominance
Genotype
Phenotype
Homozygous
dominant
Homozygous
recessive
Heterozygous
Complete dominance is defined as
Let “F” represent the inheritance of 6 fingers & 6 toes (polydactyl)
while “f” represent the inheritance of 5 fingers& 5 toes. This
inheritance patterns in an example of complete dominance.
Incomplete dominance
Genotype
Phenotype
Homozygous
dominant
Homozygous
recessive
Heterozygous
Incomplete dominance is defined as
The texture of hair in an example of incomplete dominance. Let
“H” represent the inheritance of curly hair while “h” represent the
inheritance of straight hair.
Complete dominance
Genotype
Phenotype
Codominance is defined as
.
Homozygous
dominant
Homozygous
recessive
Heterozygous
In specific types of chickens, feather color is inherited as
codominance. Let “B” represent the allele for black feathers and “b”
represent the allele for white feathers.
________________________
Genotype
Phenotype
Dwarfism is inherited as complete dominance. Let “D” represent
having dwarfism. Complete the chart on the left.
Homozygous
dominant
Homozygous
recessive
Heterozygous
________________________
Genotype
Phenotype
Homozygous
dominant
Homozygous
recessive
Heterozygous
In certain breeds of cattle when an offspring inherits 2 dominant
alleles the coat color is red. When the offspring inherits 2 recessive
alleles the coat color is white. When the offspring inherits one of
each, the coat color is roan (a pinkish coat color). Complete the
chart on the left.