Unit 10 - DNA & Cell Division
Bacteria & Uncontaminated Cultures
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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