the genetic makeup of an organism (Individual) for a specific trait such as hair
colour. They make you, you.
Phenotype
An organism's physical appearance, or visible traits. Based on the genotype. Ex:
Hair and skin colour. Specific characteristics.
Allele
Different forms of a gene. Usually exist in pairs, one from mom and one from dad.
Mutation
change in a DNA sequence that affects genetic information. Cancer can happen
because of a bad mutation. Can lead to a class of genetic disorders known as errors
of metabolism. Ex: Sun damage.
Mendel's Law of Segregation
1) Every physical trait has 2 alleles for the trait.
2) As an individual produces egg and sperm cells ( Gametes), the 2 alleles
segregate so that each gamete contains only a single allele per trait.
Homozygous
having two identical alleles for a trait. Some black people will have both alleles for
curly black hair.
Heterozygous
An organism that has two different alleles for a trait. Ex mixed baby between a
white and brown person will be mixed.
dominant allele
, An allele whose trait always shows up in the organism when the allele is present.
Black and white person will always have curly haired baby because the curly hair is
dominant.
recessive allele
An allele that is hidden when a dominant allele is present.
Exceptions to Mendel's Laws
Incomplete dominance and codominance.
incomplete dominance
Situation in which one allele is not completely dominant over another allele. You
do not know which one will be dominant over each other. There are 3 potential
phenotype outcomes. Neither one of them are dominant.
Codominance
A condition in which neither of two alleles of a gene is dominant or recessive. Ex:
Mom has A blood and dad has B blood the baby will have AB blood.
Penetrance
Of a genotype. Measure of the frequency with which a trait is actually expressed in
the population. 100 people have gene for white skin but only 80 out of that 100
have really white skin. The rest have brown skin. The penetrance of that gene is
80%.
environmental factors/expressivity
BRCA 1 and 2 are cancer genes for breast cancer. Depending on the diet which the
women eats some people who have BRCA can develop breast cancer. So
expressivity of the BRCA gene depends on the diet(environment).
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