Gene lethality
Encyclopedia
Gene
lethality occurs when two individuals of the same phenotype
mate
and a 2:1 phenotypic ratio exists in the offspring
(as long as many offspring
have been produced). Usually the homozygous dominant individuals will have been aborted
before birth
.
The number of offspring in a litter
can also indicate whether gene lethality occurs. For example, on average, the litter size of a heterozygous x heterozygous cross will be less than a heterozygous x homozygous recessive cross if homozygous dominant is lethal.
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
lethality occurs when two individuals of the same phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
mate
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
and a 2:1 phenotypic ratio exists in the offspring
Offspring
In biology, offspring is the product of reproduction, of a new organism produced by one or more parents.Collective offspring may be known as a brood or progeny in a more general way...
(as long as many offspring
Offspring
In biology, offspring is the product of reproduction, of a new organism produced by one or more parents.Collective offspring may be known as a brood or progeny in a more general way...
have been produced). Usually the homozygous dominant individuals will have been aborted
Abortion
Abortion is defined as the termination of pregnancy by the removal or expulsion from the uterus of a fetus or embryo prior to viability. An abortion can occur spontaneously, in which case it is usually called a miscarriage, or it can be purposely induced...
before birth
Birth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...
.
The number of offspring in a litter
Litter (animal)
A litter is the offspring at one birth of animals from the same mother and usually from one set of parents. The word is most often used for the offspring of mammals, but can be used for any animal that gives birth to multiple young. In comparison, a group of eggs and the offspring that hatch from...
can also indicate whether gene lethality occurs. For example, on average, the litter size of a heterozygous x heterozygous cross will be less than a heterozygous x homozygous recessive cross if homozygous dominant is lethal.