D1.2 Protein Synthesis Flashcards
Outline the process of transcription
Transcription is when a template strand of DNA is unzipped by helicase, and RNA polymerase synthesizes an mRNA strand complementary to the base sequence of the DNA (or non coding,) template strand, the mRNA is synthesized 5’ to 3’ but read 3’ to 5’.
State where in a eukaryotic cell you woudl expect to find the enzyme RNA polymerase
In the nucleolus (after transcription, mRNA leaves nuclesus to go to the ribosome for translation.
Terminology check
coding strand= non-template strand/antisense strand. mRNA follows the sequence of bases on the coding strand, except instead of thymine it is uracil (AUCG for rNA)
template (non-coding strand)/ sense strand Template strand is used to produce mRNA, and is hence complementary to mRNA.
State the enzyme responsible for breaking the hydrogen bonds between complementary strands of DNA
helicase (RNA polymerase only synthesizes the RNA strand by pairing RNA nucleotides with the exposed DNA template strand. So, while helicase initiates the unwinding process, RNA polymerase is the primary enzyme responsible for synthesizing RNA during transcription.)
What are some of the stop codons?
The standard start codon is AUG. The standard stop codon is UAG, UGA and UAA.
Outline an example of a point mutation that affects protein structure.
Hameoglobin is made up of 2 alpha haemoglobin and 2 beta haemoglobin. Haemologlobin transports oxygen for the erythrocyte. The gene that codes for the amino acid sequence with beta haemoglobin occurs on chromosome 12 and is prone to a point mutatio through a change of base from A to T (adenine to thymine) in a codon for the amino acid- glutamic acid. Due to this base substitution, the amino acid valine appears at the point instead.
However, unlike glutamic acid, valine is hyrophobic nad causes a hydrophobic spot in an otherwise hydrophiic region of protein, attracting other haemoglobin molecules, which then bind to it. In tissues with low partial oxygen, the sickle-cell haemoglobin molecules i the capillaries clump together into long fibres- distorting the shape of the cell to a sickled shape, disallowing it to transport oxygen. As a result, people with sickle cell anemia suffer inadequate delivery of oxygen to cells. the unusual haemoglobin molecule is called haemoglobin S. Sickle cell anemia (corresponding to 2 Haemoglobin S alleles, suffer from sicke cell anamie and sufer kidney and heart problems)
