Deoxyribonucleic …show more content…
This process comprises of three major stages: transcription, translation and protein synthesis. During transcription, the DNA unwinds and unzips leaving the base pairs exposed. Helicase is used in this reaction- the enzyme breaks the hydrogen bonds between the complementary bases. Activated RNA nucleotides then bind with the complementary base pairs exposed where A binds with U, G binds with C- the enzyme which catalyses the reaction is RNA Polymerase. The final mRNA strand which is produced is complementary to the original DNA strand. The mRNA is free to leave the nucleus through the nuclear pore and attach itself to a ribosome where translation takes place (OCR, 2008). The second stage is the process known as translation where the ribosome ‘reads’ the mRNA in chunks of three (codons). Each codon codes for a particular Amino Acid (AA) which is then binds to the mRNA strand using a tRNA. When a second AA is brought, a peptide bond forms between these two and this process carries on until a stop codon is reached (OCR, 2008). The process whereby AA are bought and a peptide bond forms between them is called protein synthesis. The final protein that is made during protein synthesis causes the phenotype. The term phenotype refers to the observable characteristics of an individual e.g. eye colour, hair colour or shape of …show more content…
Meiosis is the process where the male and female gametes fuse together to create a cell with the correct amount of chromosomes. Gametes contain a haploid number of chromosomes to ensure that after fertilisation, the diploid number of chromosomes is restored. The recombinant stage is when the random crossing over of genes at the same loci takes place (Appendix 8). This crossing over allows variation between organisms (OCR, 2008). Genes can be described as dominant, recessive or co-dominant. Dominant genes are inherited from both parents and are have a large influence in the phenotype of the individual. If homozygous recessive genes are present, these are also likely to appear in the phenotype. However, if the recessive genes were heterozygous they will have less of a chance of appearing in the phenotype. Co-dominance is when both alleles are dominant and therefore the phenotype of both parents will be expressed in the organism. The term heterozygous refers to two different forms of alleles and homozygous therefore refers to when the alleles are the