Unit 10 - DNA & Cell Division (Bacteria & Uncontaminated Cultures,…
Unit 10 - DNA & Cell Division
Bacteria & Uncontaminated Cultures
Petri dishes & culture media needs to be sterilised before use
use a bunsen burner to sterilise the air
tape the lid of the dish to prevent contamination of the air
required for investigating the action of disinfectants and antibiotics
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
only forms sex cells
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.
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
prophase, metaphase, anaphase, telophase
long strands of DNA consist of alternating sugar and phosphate sections. attached to each sugar is one of four bases: A,C,G,T
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
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.