chapter 10- biology

crossing over

(genetic recombination) a process, occuring during meiosis, in which homologous chromosomes exchange reciprocal portions of themselves.

oogonia

(singular,oogonium) the diploid cells that are starting female cells in gamete (egg) production. Diploid oogonia develop into diploid primary oocytes, which give rise to haploid secondary.

2n

in a living cell, the condition of being diploid: of having two sets of chromosomes.

n

in a living cell, the condition of being haploid: of having a single set of chromosomes

polar body

nonfunctional cell produced during meiosis in females.

haploid

possessing a single set of chromosomes. Human gametes (eggs and sperm) are haploid cells because they have only a single set of chromosomes. All other cells in the human body are diploid, meaning the possess two sets of chromosomes. Some organisms are strictly haploid. Bacteria, for example, have only a single chromosome, making them haploid.

diploid

possessing two sets of chromosomes. all human cells are diploid with the exception of human gametes (eggs and sperm), which are haploid. Such haploid cells possess only a single set of chromosomes.

asexual reproduction

reproduction that occurs without the union of two reproductive cells (sexual reproduction). Offspring produced through asexual reproduction are genetically identical to their parent organism.

primary spermatocyte

a diploid cell in a male that will undergo meiosis to produce haploid secondary spermatocytes, which ultimately give rise to mature sperm cells

primary oocyte

a diploid cell produced in females that may mature into an egg, intially by giving rise to haploid secondary oocytes. After the female reaches puberty, an average of one oocyte per month is selected to continue the process of maturation in the ovary.

gamete

a haploid reproductive cell, either egg or sperm

sexual reproduction

a means of reproduction in which the nuclei of the reproductive cells from two separate organisms fuse to produce offspring.

meiosis

a process in which a single diploid cell divides to produce four haploid reproductive cells.

spermatogonia

diploid cells that are the starting cells in sperm production in males. Spermatogonia are reproductive stem cells in that, when dividing, each of them produces one primary spermatocyte (which will develop into four mature sperm cells) and one spermatogonium

sex chromosome

the chromosomes that determine the sex of an organism. the X or Y chromosomes in human

tetrad

the grouping formed by the linkage of two homologous chromosomes in prophase 1 of meiosis. the four sister chromatids involved in this linkage give it the name tetrad.

independent assortment

the random distribution of homologous chromosome pairs on differing sides of the metaphase plate during meiosis

life cycle

the repeating series of steps that occur in the reproduction of an organism.