Bio - Chapter 8: Cellular Reproduction: Cells from Cells

Cell division

2 “daughter” cells are produced that are genetically identical to each other and the “parent” cell

Chromosomes

Structures that contain most of the cell’s DNA

Asexual reproduction

Single-celled organisms reproduce by dividing in half, producing genetic replicas of the parent cell

Clone

Group of genetically identical individuals

Sexual reproduction

Requires fertilization of egg by sperm

Gametes

Egg and sperm, production involved meiosis

Diploid(2n)

2 pairs of homologous chromosomes

Haploid(n)

One set of each chromosome

Triploid(3n)

3 copies of each chromosome

Homologous chromosomes

Chromosomes of the same type with the same genes in the same location

Allele

Homologous chromosomes have the same genes, they can have different versions of the same gene

Genotype

What genes are present on a chromosome

Phenotype

Physical expression of those genes

Chromatin

Fibers composed of roughly equal amounts of DNA and protein molecules

Histones

Proteins used to package DNA in eukaryotes

Nucleosomes

Consist of DNA wound around several histone molecules

Sister chromatids

Contain identical genes

Centromere

2 sister chromatids are joined together tightly at a narrow “waist”

A cell cycle

The ordered sequence of events that extend from the time a cell is first formed from a dividing parent cell to its own division into 2 cells

Interphase

Most of the cell cycle is spent here, lasts for 90% of the cycle

DNA replication

The S phase, “synthesis” of DNA

Mitosis

The nucleus and its contents divide evenly into 2 daughter nuclei

Cytokinesis

The cytoplasm and other organelles are divided into 2

Prophase

Chromosomes condense, nuclear envelope breaks down, mitotic spindle forms from centrosomes

Metaphase

Chromosomes line up at the metaphase plate in center of nucleus and mitotic spindle binds to centromere

Anaphase

Sister chromatids are separated by mitotic spindle

Telophase

Nuclear envelope reforms, cytokinesis occurs with cleavage furrow

Mitotic spindle

A football shaped structure of microtubules that guides the separation of the 2 sets of daughter chromosomes

Cytokinesis

Usually begins during telophase, divides the cytoplasm, and is different in plants and animal cells

Cell plate

A membranous disk

Somatic cell

46 chromosomes

Life cycle

Sequence of generation-to-generation stages

Fertilization

Haploid sperm fuses with haploid egg

Zygote

Resulting fertilized cell

Crossing over

Homologous chromosomes pair up and exchange sections, provides genetic variation

Meiosis l

Homologous pairs separate

Meiosis ll

Chromatids separate

Nondisjunction

Members of a chromosome pair and fail to separate at anaphase, producing gametes with abnormal numbers of chromosomes, and can occur during meiosis

Trisomy 21

47 chromosomes, down syndrome

Tumors

Abnormally growing masses of body cells

Benign tumor

Remains at the original site

Malignant tumor

Spreads into tissues, interrupts organ function

Metastasis

Spread of cancer cells beyond original site