Unit 10 - DNA & Cell Division

Bacteria & Uncontaminated Cultures

click to edit

Cell Division

DNA

Uncontaminated Cultures

Bacteria

multiply by single cell division as often as once every 20 mins

can be grown in a nutrient broth solution or as colonies on an agar plate

Petri dishes & culture media needs to be sterilised before use

required for investigating the action of disinfectants and antibiotics

use a bunsen burner to sterilise the air

tape the lid of the dish to prevent contamination of the air

long strands of DNA consist of alternating sugar and phosphate sections. attached to each sugar is one of four bases: A,C,G,T

genetic material in the nucleus is DNA. The DNA is contained in chromosomes.

chromosomes carry a large number of genes. In a body's cell there should be 23 pairs of chromosomes, amounting to 46.

A sequence of three bases is the code for a particular amino acid

C is always liked to a G and T is always linked to A

Meiosis

Mitosis

only forms sex cells

two cell divisions, haploid cells, 4 cells formed, genetic variation

used to make identical cells to replace damaged cells.

Before a cell divides, its chromosomes are copied exactly. The DNA molecule is made of two strands. As each of the two strands separate, new strands are made alongside each of them, thereby making two new copies.

one cell division, diploid cells, 2 cells formed, no genetic variation

At fertilisation, the nuclei of the sperm and an egg join to form the zygote. The zygote contains 23 pairs of chromosomes - 23 single chromosomes from the sperm, and 23 single chromosomes from the egg, creating the 46 chromosomes for all body cells. It also means the zygote contains a complete set of chromosomes from each parent.

prophase, metaphase, anaphase, telophase