Chapter 14: Cell Division

Cell Continuity

all cells develop from pre-existing cells

Chromosomes

thread-like structures made of DNA and proteins

Haploid Cells

a cell with one set of chromosomes

Diploid Cells

a cell with two sets of chromosomes

Homologous Pair

consists of two chromosomes that have genes for the same feature at the same position

Genes

many units of DNA which contain the instructions for the formation of proteins

Enzymes

control the activity of the cells

Locus

location of a gene on a chromosome

Genome

all the genes in an organism

Cell Cycle

the process a cell goes through each time it divides

Interphase

stage when the cell is not dividing, is 90% of the cells life

Activities during Interphase

DNA replication, new mitochondria and chloroplasts produced, respiration and photosynthesis, formation of enzymes and proteins

Mitosis

form of nuclear division where one nucleus divides to form two nuclei, each containng the same number of chromosomes with identical genes

Stages of Mitosis

prophase, metaphase, anaphase, telophase

Prophase

chromatin condenses into chromosomes, nucleus disappears, spindle fibres appears, nucleous breaks down and nuclear membrane breaks down

Metaphase

sister chromatids migrate to the equator of the cell, spindle fibres from each centriole attach themselves to the centromere of sister chromatids

Anaphase

sister chromatids split, spindle fibres contract and pull chromosomes to the poles

Telophase

spindle fibres disassemble, nuclear membrane forms around each new nucleus, chromosomes become chromatin, cleavage furrow forms to help divide the cells

Cytokinesis

splitting of two cells

Cytokinesis in Plants

vesicles migrate to the equator of the cell, fuse and form a cell plate, middle lamella is the region between the plant cell walls

Functions of Mitosis

asexual reproduction, growth, repair

Cancer

group of disorders where cells lose their ability to control the rate of mitosis and the number of times mitosis takes place

Benign Tumours

tumours that are caused by viruses and stop dividin after some time

Examples of Benign Tumours

warts, skin tags

Malignant Tumours

invade other cells and move around the body, divide indefinitely

Metastasis

movement of cancer cells around the body

Oncogenes

cancer-causing genes

Carcinogens

any chemical, biological or physical agent that can cause cancer

Treatment of Cancer

surgery, radiotherapy, chemotherapy

Meiosis

division of the nucleus which produces four daughter nuclei, each containing half the chromosome number of the original cell

Genetic Recombination

allows for genetic variation during meiosis