BIOL 3200: CH 3: Chromosome Transmission During Cell Division and Sexual Reproduction

Anaphase

Phase of mitosis in which the chromosomes separate and move to opposite ends of the cell

Asexual reproduction

Process by which a single parent reproduces by itself

Autosomes

Any chromosome that is not a sex chromosome

Binary fission

A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

Bivalents

A structure in which 2 pairs of homologous sister chromatids have synapsed with one another

Cell cycle

series of events that cells go through as they grow and divide

Cell plate

the precursor of a new plant cell wall that forms during cell division and divides a cell into two

Centrioles

a minute cylindrical organelle near the nucleus in animal cells, occurring in pairs and involved in the development of spindle fibers in cell division.

Centromere

Region of a chromosome where the two sister chromatids attach

Centrosomes

Microtubule-organizing centers that help to form and organize the mitotic spindle during mitosis

Chiasma (chiasmata)

The microscopically visible site where crossing over has occurred between chromatids of homologous chromosomes during prophase I of meiosis.

Chromatids

one of two identical "sister" parts of a duplicated chromosome

Sister chromatids

Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II.

Chromatin

Substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones

Chromosome theory of inheritance

A basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.

Chromosomes

threadlike structures made of DNA molecules that contain the genes

Cleavage furrow

The area of the cell membrane that pinches in and eventually separates the dividing cell

Condensed chromosomes

The process in which chromosomes in a chromatin state (partially folded DNA) folds further to create a tight chromosome.

Crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Cytogenetics

the field of genetics that involves the microscopic examination of chromosomes

Cytogeneticist

a scientist who studies chromosomes microscopically

Cytokinesis

Division of the cytoplasm during cell division

Decondensed

chromosomes that form a less compact structure

Diakinesis

the fifth and last stage of the prophase of meiosis, following diplotene, when the separation of homologous chromosomes is complete and crossing over has occurred.

Diploid

containing two complete sets of chromosomes, one from each parent.

Diplotene

synaptonemal complex disappears, chiasma still present

Egg cell

female reproductive cell

Eukaryotes

organisms made up of one or more cells that have a nucleus and membrane-bound organelles

Gametes

sex cells

Gametogenesis

process by which gametes are produced through the combination of meiosis and other maturational changes

Germ cells

Reproductive cells that give rise to sperm and ovum

Haploid

An organism or cell having only one complete set of chromosomes.

Heterogametic

sex chromosomes are of different types

Heterogamous

produce two morphologically different types of gametes

Homogametic

sex chromosomes are of one type

Homologs

Members of a pair of chromosomes

Karyotype

the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.

Kinetochore

A specialized region on the centromere that links each sister chromatid to the mitotic spindle.

Interphase

the resting phase between successive mitotic divisions of a cell, or between the first and second divisions of meiosis.

Isogamous

describes a species that makes morphologically similar gametes

Leptotene

the first stage of the prophase of meiosis, during which each chromosome becomes visible as two fine threads (chromatids).

Locus (loci)

the location of a gene

Meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

Metaphase

second phase of mitosis, during which the chromosomes line up across the center of the cell

Metaphase plate

Plane midway between the two poles of the cell where chromosomes line up during metaphase.

Microtubules (3 types)

cilia, flagella, centrioles

Microtubule-organizing centers

a structure found in eukaryotic cells from which microtubules emerge; centrosomes, spindle poles, basal bodies

Mitosis

part of eukaryotic cell division during which the cell nucleus divides

Mitotic spindle (apparatus)

composed of microtubules, cell cytoskeleton, and involved in the organized movement of chromosomes during the cell cycle

Nucleoid

A non-membrane-bounded region in a prokaryotic cell where the DNA is concentrated.

Nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

Oogenesis

the production, growth, and maturation of an egg, or ovum

Organelles

A tiny cell structure that carries out a specific function within the cell

Pachytene

synapsis complete, crossing over

Prometaphase

The second stage of mitosis, in which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the chromosomes.

Prophase

Chromosomes become visable, nuclear envelop dissolves, spindle forms

Prokaryotes

Single-celled organisms without a nucleus or membrane bound organelles

Reciprocal cross

a cross in which the phenotypes of the male and female are reversed compared with a prior cross

Restriction point

The point in the G1 stage where the cell is committed to continue through the rest of the cell cycle and divide. (Some never reach this point, entering a nondividing phase G0)

Sex chromosomes

Chromosomes that determine the sex of an individual

Somatic cell

any cell of a living organism other than the reproductive cells.

Sperm cells

male reproductive cells

Spermatogenesis

Formation of sperm

Spindle pole

Centrosome from which microtubules radiate to form the mitotic spindle.

Synapsis

the pairing of homologous chromosomes during meiosis

Synaptonemal complex

A zipper-like protein structure that causes replicated homologs to become physically connected during prophase of meiosis I; sets the stage for crossing over.

Telophase

the final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.

Testcross

cross between an organism with an unknown genotype and an organism with a recessive phenotype

Tetrad

structure containing 4 chromatids that forms during meiosis

X-linked alleles (genes)

genes (or alleles of genes) that are physically located within the X chromosome.

X-linked inheritance

A pattern of inheritance in which a recessive gene is carried on the X chromosome, so that males are more likely to be affected

Zygotene

synapsis begins, synaptonemal complex forming