CH 13 BIO ploidy, mitosis, meiosis
homolog
A homologous gene (or homolog) is a gene inherited in two species by a common ancestor. While homologous genes can be similar in sequence, similar sequences are not necessarily homologous. Orthologous are homologous genes where a gene is found in two different species, but the origin of the gene is a common ancestor.
homologous pair
Homologous chromosomes are made up of chromosome pairs of approximately the same length, centromere position, and staining pattern, for genes with the same corresponding loci. One homologous chromosome is inherited from the organism's mother; the other is inherited from the organism's father.
chromosome set
Two gametes form a diploid zygote with twice this number (2n, the zygotic or diploid number) i.e. two copies of autosomal chromosomes. For humans, a diploid species, n = 23. A typical human somatic cell contains 46 chromosomes: 2 complete haploid sets, which make up 23 homologous chromosome pairs.
haploid
a cell containing only one set of chromosomes
diploid cells
a cell containing two sets of chromosomes (2n), one set inherited from each parent
recombinant chromosomes
a chromosome created when crossing over combines the DNA from two parents into a single chromosome
sexual reproduction
a type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the parents
polyploid
cells and organisms are those containing more than two paired (homologous) sets of chromosomes. Most species whose cells have nuclei (Eukaryotes) are diploid, meaning they have two sets of chromosomes—one set inherited from each parent.
independent assortment
he principle, originated by Gregor Mendel, stating that when two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together. Expand. Also called Mendel's second law, Mendel's law.
ploidy
is a measure of the number of chromosomes in a cell. Chromosomes are the threadlike structures that contain the genetic material known as DNA.
cell cycle
is a series of events that takes place in a cell as it grows and divides. A cell spends most of its time in what is called interphase, and during this time it grows, replicates its chromosomes, and prepares for cell division. The cell then leaves interphase, undergoes mitosis, and completes its division.
chiasma
the X-shaped, microscopically visible region where homologous non sister chromatids have exchanged genetic material through crossing over during meiosis, the two homologs remaining associated due to sister chromatid cohesion
zygote
the diploid product of the union of haploid gametes during fertilization; a fertilized egg
meiosis I
the first division of a two-stage process of cell division in sexually reproducing organisms that result in cells with half the number of chromosome sets as the original cell
asexual reproduction
the generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts) - in most cases, the offspring are genetically identical to the parent
synapsis
the physical connection of replicated homologous chromosomes during prophase I of meiosis
crossing over
the reciprocal exchange of genetic material between non sister chromatids during prophase I of meiosis
meiosis II
the second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell
fertilization
the union of haploid gametes to produce a diploid zygote