Chapter 9 Definitions Flashcards
Genetic recombinations
The process by which the combinations of alleles for different genes in two parental individuals become shuffled into new combinations in offspring individuals
Homologuos sequences
Similar. Characteristics that are similar in two species because they inherited the genetic basis of the trait from a common ancestor
Gametes
A haploid cell, an egg or sperm. Haploid cells fuse during sexual reproduction to form a diploid zygote.
Meiosis
The division of diploid cells to haploid progeny. Consisting of two sequential rounds of nuclear and cellular division
Sexual Reproduction
The mode of reproduction in which male and female parents produce offspring through the union of egg and sperm generated by meiosis
Fertilization
The fusion of the nuclei of an egg and sperm cell, which initiates development of a new individual.
Zygote
A fertilized egg
Haploid
An organism or cell with only one copy of each type of chromosome in its nuclei
Diploid
An organism or cell with two copies of each type or chromosome in its nuclei
Sporophyte
An individual of the diploid generation produced through fertilization in organisms that undergo alternation of generations; it produces haploid spores
Gametophyte
An individual of the haploid generation produced when a spore germinates and grows directly by mitotic divisions in organisms that undergo alternation of generations.
Spore
A haploid reproductive structure, usually a single cell, that can develop into a new individual without fusing with another cell; found in plants, fungi, and certain protists.
Maternal vs. paternal chromosomes
Maternal chromosomes are derived from the female parent of an organism and paternal chromosomes are derived from the male parent of an organism.
Homologous
Similar
Nondisjunction
The failure of homologous pairs to separate during the first meiotic division or of chromatids to separate during the second meiotic division.
