Practise allele definitions, protein synthesis, selective gene expression and chromosome-number questions using mRNA, specialised cells, chromosome pairs and ploidy evidence.
A scientist investigated sexual reproduction in flowering plants.
Fig. 2.1 shows the procedure for crossing two plants of the same species.
The scientist collected the seeds and germinated them. The leaves and flowers of the offspring plants showed phenotypic variation as they were not all identical to the parent plants.
The scientist then investigated the chromosomes of all the offspring plants and found that they had exactly the same number of chromosomes as the parent plants.
Define the term chromosome.
A gene is involved in the production of the enzyme alcohol dehydrogenase.
Define the term gene.
Describe the role of ribosomes in the synthesis of proteins such as enzymes.
Fig. 5.1 shows the stages involved in protein synthesis.
Fig. 5.1
State the names of the parts labelled X, Y and Z in Fig. 5.1.
X
Y
Z
State what determines the sequence of the amino acids in the protein that is produced.
Explain why the sequence of amino acids is important in the production of receptor molecules for neurotransmitters.
Explain why body cells can have different specialised functions even though they contain the same genes.
Allele frequency in a population can be changed by natural selection and artificial selection.
State the meaning of the term allele.