AS and A Level Biology

State that some mineral ions and organic compounds can be transported within plants dissolved in water

Explain mass flow in phloem sieve tubes down a hydrostatic pressure gradient from source to sink

Describe the distribution of xylem and phloem in transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants

Relate the structure of xylem vessel elements, phloem sieve tube elements and companion cells to their functions

State that a polypeptide is coded for by a gene and that a gene is a sequence of nucleotides that forms part of a DNA molecule

Explain that a gene mutation is a result of substitution or deletion or insertion of nucleotides in DNA and outline how each of these types of mutation may affect the polypeptide produced

State that a gene mutation is a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide

State that the strand of a DNA molecule that is used in transcription is called the transcribed or template strand and that the other strand is called the non-transcribed strand

Explain that, in eukaryotes, the RNA molecule formed following transcription (primary transcript) is modified by the removal of non-coding sequences (introns) and the joining together of coding sequences (exons) to form mRNA

Describe how the information in DNA is used during transcription and translation to construct polypeptides, including the roles of: • RNA polymerase • messenger RNA (mRNA) • codons • transfer RNA (tRNA) • anticodons • ribosomes