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.
A gene is involved in the production of the enzyme alcohol dehydrogenase.
Define the term gene.
Allele frequency in a population can be changed by natural selection and artificial selection.
State the meaning of the term allele.
Sex in cats is determined in the same way as in humans.
Complete the diagram below to show how sex is determined in cats.
offspring ratio
Fig. 5.1 shows the stages involved in protein synthesis.
Fig. 5.1
State what determines the sequence of the amino acids in the protein that is produced.
Fig. 2.1 shows a dwarf sunflower and a tall sunflower, Helianthus annuus. The height of the dwarf sunflower is 0.45 m and the height of the tall sunflower is 4.5 m .
not to scale
Dwarf plants like the one in Fig. 2.1 have mutant alleles.
Shoot growth in plants is controlled by auxins. An enzyme in shoot tips converts molecules of an amino acid into auxins as shown in Fig. 2.2.
Fig. 2.2
Explain how a mutation in DNA results in an abnormal enzyme which does not catalyse the reaction shown in Fig. 2.2.
Fig. 6.1 is a diagram of a cell that shows how DNA is involved in protein synthesis.
Fig. 6.1
DNA controls cell function by controlling the production of proteins.
State the name of one type of protein.
A gene is involved in the production of the enzyme alcohol dehydrogenase.
Describe the role of ribosomes in the synthesis of proteins such as enzymes.
Fig. 6.1 shows some cells from the shoot tip of an onion, Allium cepa.
Fig. 6.1
Some cells in shoot tips become leaf cells and others become cells in the stem or in flowers.
Explain why it is important that only some of the genes in cell A are expressed in these cells.
Fig. 3.2 shows the life cycle of a fern. The life cycle of a fern has some similarities and some differences compared with the life cycles of other plants.
The letters represent processes that occur during the life cycle.
The haploid stages of the life cycle are represented by (n).
The diploid stages of the life cycle are represented by (2 n).
Fig. 3.2
The adult sporophyte has 1200 chromosomes in its body cells.
State the number of chromosomes in the body cells of the gametophyte.
Fig. 6.2 shows a plant tissue in which cells are dividing by mitosis.
Fig. 6.2
Cell J in Fig. 6.2 is an example of a diploid cell.
State what is meant by the term diploid.
The Tasmanian devil is an animal with seven pairs of chromosomes in each body cell.
The diagram shows the chromosomes in a cell from a Tasmanian devil.
Which statement is correct?
The cell is a haploid cell containing pairs of chromosomes.
The cell is a diploid cell with no pairs of chromosomes.
The cell is a haploid cell with no pairs of chromosomes.
The cell is a diploid cell containing pairs of chromosomes.