3.1 Genes

• The position of a gene on a chromosome is called the locus.
• A gene is q DNA sequence that encodes for a particular trait.
• An allele is a gene.
• An allele is a specific gene variant which does for a particular trait ie. blue eyes.
• Gene mutation is a change in the nucleotide sequence of a section of DNA which can be beneficial, detrimental or neutral.
• Silent mutations are neutral mutations which have no effect on the functioning of the specific feature as the same proteins are still coded for.
• Missense mutations have a positive affect on the function of a trait caused by a change in the proteins created.
• Nonsense mutations have a detrimental affect on the function of a trait caused by a change in the proteins created.
• Alleles differ from each other by one or a few bases.
• There are 4 mutation types: substitution, addition, deletion or inversion.
• Sickle cell anaemia is an example of substitution mutation of the 6th codon for the beta chain of haemoglobin.
• Sickle cell anaemia causes haemoglobin to form insoluble fibrous strands increasing exhaustion, changing the red blood cell shape into a sickle, increasing the risk of clots and reducing red blood cell count as they are destroyed more rapidly.
• Anaemia is a deficiency of healthy red blood cells.
• The genome is the totality of genetic information of a cell, organism or organelle.
• Humans have 46 chromosomes.
• Humans have around 3 billion base pairs.
• Humans have around 21,000 genes.
• The Human Genome Project was a project to sequence the entire base sequence of human genes (human genome).
• The Human Genome Project enabled better mapping of genes, the ability to screen people for genetic diseases, breakthroughs in medicine and the ability to investigate one's ancestry.
• Number of genes is not an indicator of biological complexity.
• Expressed sequence tags are recongisable sequences that occur often which can be deduced to code for a particular trait.