Biology B1 - B5

Topics: DNA, Cell, Bacteria Pages: 19 (4951 words) Published: February 14, 2013
Biology Notes
B1 NOTES: You and Your Genes
Chromosomes: They are found inside the nucleus of cells. They are X Shaped Objects that Contain DNA. Each Chromosome is made from two Chromatids. Chromosomes are held together by a disc called a centromere. Chromosomes are always found in Pairs. | |

A| T|
G| C|
C| G|
DNA: It Stands for Deoxyribonucleic acid. DNA is Made from Nucleic acids of ten (referred to as bases). The four bases are Adenine (A) which always pairs with Thymine (T) and Cytosine (C) which always pairs with Guanine (G). | |

T| C|
A| G|
T| G|

Genes: A gene is the short length of the chromosome which is a molecule of a DNA. Genes can exist in Different Versions. Different Versions of the same gene are known as ALLELES. Each gene codes for a specific Protein. Some proteins are Structural, meaning they can form skin, hair, blood and cytoplasm. Others are Functional (enzymes) controlling chemical reactions such as respiration or digestion. Genetic Information is stored by Genes who are arranged on Chromosomes. Variation: This is the Difference between humans. There are two types of variation. The First is Genetic Variation (Caused by your Genes and can’t be changed e.g. your natural hair colour, eye colour). The Second is Environmental Variation (Caused by your surrounding and can be changed e.g. Dying your Hair, Ear Piercings). Genetic Variation: Caused by the DNA in the cells in your body. We Can’t Change this. Environmental Variation: Caused by your Surroundings, Family and Friends. We can Change this. Determining Your Gender: A Sperm Cell has an X chromosome and a Y chromosome. An Egg Cell has two X Chromosomes. If the fertilised egg has a X Chromosome from the sperm the Foetus will be a Girl if it has a Y Chromosome (the Chromosome carrying Testosterone) the Foetus will Be a Boy. There is a 50:50 Chance of Having a Boy or a Girl. Further Gender Determination

Chromosome pair 23 is known as the Sex Chromosomes. There are two Different types of of Chromosome 23 – The X and Y chromosome. The only Difference is that the Y chromosome carries the gene for testosterone, X does not. All Cells carry at least one X Chromosome. Sperm Cells carry either a Y or X chromosome. Allele – A different version of the same gene.

Heterozygous – When There are two types of an allele in the genotype e.g. Bb – Brown. Homozygous – When there is only one type of Allele in the genotype e.g. BB(-Brown) or bb(-Blonde). B = Dominant – Always Expressed, b = Recessive – only expressed in a Homozygous genotype. Natural Cloning

* The Hydra (Plant) Shows Budding
* Asexual Reproduction - The Spider Plant and Strawberries often reproduce this way. Twins: They are formed by the fertilised egg splitting in half and the two halves turn into to two identical babies. Artificial Cloning

For many years, mammals have been cloned by splitting embryos – Artificial Cloning. There are two types of Artificial Cloning Cloning Way 1
1. They take an egg cell from one mammal.
2. A Body Cell is taken from a second mammal (the same mammal as the first) 3. The egg cell nucleus is removed from the cell
4. The body cell nucleus is also removed
5. The Nucleus from the body cell is inserted into the egg cell to make a clone of the Second Mammal. 6. The egg cell divides and is put into the uterus of the first Mammal. The Clone grows into a mature mammal. Cloning Way 2

It isn’t just Reproductive Cloning (Cloning People/mammals) we could use this technology for. Cloning human cells may be useful in treating humans. Reproductive Cloning – When a baby is born from cloning

Stem Cells
A stem cell is an undifferentiated cell which means they can turn into any type of cell required. They can therefore be used to...
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