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22 (a) (i) Fig - OCR Gateway - GCSE Biology - Question 22 - 2021 - Paper 1
Question 22
22 (a) (i) Fig. 22.1 shows the cell cycle. The letters represent different stages. Which processes happen during stage S and stage M? Write your answers in the tab... show full transcript
Worked Solution & Example Answer:22 (a) (i) Fig - OCR Gateway - GCSE Biology - Question 22 - 2021 - Paper 1
Step 1
Which processes happen during stage S and stage M?
Answer
During stage S, DNA replication occurs, where the chromosomes are duplicated. In stage M, which is the mitotic phase, processes like mitosis and cytokinesis occur, leading to the movement and division of chromosomes into two daughter cells.
Step 2
Step 3
Describe how cells make proteins for growth and explain why the drug Actinomycin D inhibits some but not all protein synthesis.
Answer
Cells make proteins through a process called transcription and translation. First, in transcription, the DNA sequence is transcribed into messenger RNA (mRNA). The mRNA then travels to ribosomes, where translation occurs, and amino acids are assembled into proteins.
Actinomycin D inhibits some protein synthesis because it binds to the unzipped DNA and prevents RNA polymerase from synthesizing mRNA during transcription. However, it does not affect pre-existing RNA or the translation process of proteins already in the ribosomes using that RNA.
Step 4
Explain how the structure of DNA determines the type of protein made:
Answer
The structure of DNA consists of sequences of nucleotides, which are arranged in a specific order. Each triplet of nucleotides, known as a codon, codes for a specific amino acid. The order of these codons ultimately determines the sequence of amino acids in a protein, which defines the structure and function of that protein.