Genetics 1 Flashcards
Define character/trait.
A heritable feature that varies among individuals is called a character.
What are alleles?
He hypothesized that there are alternative versions of genes (alleles), the units that determine heritable traits.
Do all traits appear equally?
Dominant traits would be inherited even when the two parent flowers were different, while recessive traits could only be passed down with two of the same parental traits.
Define phenotype and genotype.
Phenotype is a set of observable physical traits. (purple, white )
Genotype is the genetic information of an organism.
What are the two different versions of genes?
Heterozygous: having two different alleles for a gene
Homozygous: having two copies of the same allele for a gene
What is the law of segregation?
A sperm or egg carries only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes.
We saw this during meiosis!
This statement is called the law of segregation.
What is the law of independant assortment?
The inheritance of one character has no effect on the inheritance of another
This is known as the law of independent assortment
What is the chromosomal law of inheritance?
The chromosome theory of inheritance holds that:
-genes occupy specific loci (positions) on chromosomes
-chromosomes undergo segregation and independent assortment during meiosis.
What are the phenotypic ratios according to the law of independant assortment?
Following the law of independent assortment, the phenotypic ratios for:
One gene with 2 alleles: 3:1
Two genes with 2 alleles: 9:3:31
Explain the inheritance of people with recessive disorders?
Most people who have recessive disorders are born to normal parents who are both heterozygotes—that is, parents who are carriers of the recessive allele for the disorder but are phenotypically normal.
What is incomplete dominance?
If the offspring has a phenotype different from the parents and looks more like an intermediate of the two traits, that trait shows incomplete dominance
What is pleiotropy? Give an example of it.
Pleiotropy occurs when one gene influences multiple characters.
Sickle-cell disease is a human example of pleiotropy.This disease affects the type of hemoglobin produced and the shape of red blood cells, and causes anemia and organ damage.
What is polygenic inheritance. Give example.
A single character can be influenced by many genes. Polygenic traits may show up on a spectrum across a population.
(human height, skin colour)
What can be the explanation for phentoypic changes in identical twins?
Many traits are affected, in varying degrees, by both genetic and environmental factors.
This includes sun exposure, nutrition, environmental pollutants etc.
When is law of independant assortment applicable? What is the exception called?
The law of independent assortment only applies to genes on separate chromosomes
Genes located together on the same chromosome tend to be inherited together
These are known as linked genes.
