The passing of traits from parents to offspring is called heredity. If a trait reappears in the second generation after disappearing in the first generation, this is defined as recessive. Heredity was first discovered by Gregor Mendel through his studies on pea plants.
Genotype refers to the combination of genes forming a specific trait while phenotype is the appearance of an organism. A heterozygous trait is formed by a combination of both dominant and recessive genes (dominant refers to the trait that masks the recessive trait and is observed in the first generation).
Law of segregation – When sex cells are produced, the copies of the gene are separated such that each cell receives a copy of the gene.
Law of independent assortment – This law is also known as the inheritance law and states that alleles of a gene assort independently for form gamete.
Law of dominance – This states that if two parents are crossed with different pure traits, only one trait will appear in the next generation and this trait is called the dominant trait while the masked trait is called the recessive trait.
If studying only one pair of a contrasting trait, this is called a monohybrid cross. Dihybrid cross is when two pairs of the trait are being studied. The difference between complete and incomplete dominance is that complete dominance involves the dominant trait masking the recessive trait while incomplete dominance involves both alleles contributing to an individual trait (this forms a completely different trait than that of the parent) e.g white allele and black allele forming grey trait. If two contrasting alleles are expressed equally, e.g white allele and brown allele forming white and brown trait, this is called codominance.
If a gene is controlled by a single gene, this is described as monogenic and such phenotype shows discontinuous variation. Genes controlled by more than one gene are polygenic and usually show continuous variation.
When you cross an individual of the unknown with an individual with known homozygous genotype, this is called a test cross and is done to determine unknown genotypes.
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Heredity
The passing of genetic traits from parent to offspring
Recessive
A trait that reappears in the second generation after disappearing in the first generation when parents with different traits are bred
Gregor Mendel
Austrian Monk who studied pea plants and discovered the principles of heredity
Genotype
The combination of genes for one or more specific traits
Heterozygous
A trait that is formed from a recessive and dominant allele
Phenotype
An organism’s appearance or other detectable characteristic
Gene
One set of instructions on a strand of DNA for an inherited trait
Incomplete dominance
When two traits are not completely dominant over one another
Sickle cell anemia
The recessive genetic disorder that can affect red blood cells
Allele
One of the alternative forms of a gene that govern for a certain characteristic
Dominant
The trait observed in the first generation when parents that have different traits are bred
Trait
A genetically determined characteristic
Characteristic
A feature that has different forms in a population
Homozygous
A trait formed from either 2 dominant alleles or 2 recessive alleles
Punnett square
Used to organize all the possible combinations of offspring from particular parents
Law of Segregation
When any individual produces sex cells, gametes, the copies of a gene seperate, so that each sex cell, gamete, receives only one copy. A gamete will receive one allele or the other.
Law of Independent Assortment
Alleles of different genes assort independently of one another during gamete formation; also known as “Inheritance Law”
Law of Dominance
In a cross of parents that are pure for different traits, only one form of the trait will appear in the next generation, that is the dominance trait
