Molecules and Cells: Mitosis and Meiosis Vocabulary

chromosome

a structure composed of a DNA molecule and associated proteins

chromatin

the material that makes up eukaryotic chromosomes; consists of a DNA molecule complexed with histone proteins

chromatid

one strand of a replicated chromosome, with its associated proteins

sister chromatids

the two strands of a replicated chromosome, become independent chromosomes when they separate during mitosis

centromere

the structure that joins sister chromatids

kinetochores

the structures on sister chromatids where microtubules attach

microtubule-organizing center

any structure that organizes microtubules

centrosome

the microtubule-organizing center in animals and some plants

centrioles

cylindrical structures that comprise microtubules, located inside animal centrosomes

unreplicated chromosome

a chromosome that consists of one double-helical molecule of DNA packaged with proteins

replicated chromosome

a chromosome that has been copied; consists of two identical chromatids, each containing one double-helical DNA molecule

homologous chromosomes (homologs)

in a diploid organism, chromosomes that are similar in size, shape, and gene content

non-sister chromatids

chromatids belonging to homologous chromosomes

bivalent (tetrad)

homologous replicated chromosomes that are joined together during prophase I and metaphase I of meiosis

haploid number

the number of different types of chromosomes in a cell; symbolized n

diploid number

the number of chromosomes present in a diploid cell; symbolized 2n

ploidy

the number of each type of chromosome present

haploid

having one of each type of chromosome (n)

diploid

having two of each type of chromosome (2n)

polyploid

having more than two of each type of chromosome; cells may be triploid (3n), tetraploid (4n), hexaploid (6n), etc