Practise 16.1 inheritance by interpreting meiosis diagrams, tracking chromosome sets and explaining how gamete formation and fertilisation create variation.
In sexual reproduction, meiosis occurs to produce haploid gametes from a diploid cell.
Explain the meaning of the terms haploid and diploid.
Describe the behaviour of chromosomes during the main stages of meiosis I in animal cells.
prophase I
metaphase I
anaphase I
telophase I
Many different genes are involved in the production of pigments in mammals. One example is the TYR gene.
In humans the TYR gene is located on chromosome 11.
Fig. 6.1 shows the homologous pair for chromosome 11.
Fig. 6.1
Homologous chromosomes have the same genes located at the same loci. State one other feature shared by homologous chromosomes.
Meiosis is described as a reduction division because the number of chromosomes in the daughter cells is reduced by half.
Table 5.1 describes some of the events that take place during four of the different stages of meiosis in an animal cell.
Table 5.1
Complete Table 5.1 by:
- outlining the behaviour of the spindle fibres during anaphase I
- identifying the stage of meiosis in which spindle fibres re-form the spindle in daughter cells
- drawing a diagram to show telophase II.
You do not need to add labels to your diagram showing telophase II.
Explain the need for a reduction division during meiosis.
In sexual reproduction, meiosis occurs to produce haploid gametes from a diploid cell.
Explain the meaning of the terms haploid and diploid.
Meiosis is described as a reduction division because the number of chromosomes in the daughter cells is reduced by half.
Explain the need for a reduction division during meiosis.
Fig. 8.1 shows a cell from the testis of a locust at the late prophase I stage of meiosis.
Fig. 8.1
Explain how the behaviour of the chromosomes in prophase I of meiosis results in the appearance shown in Fig. 8.1.
Describe the behaviour of chromosomes during the main stages of meiosis I in animal cells.
prophase I
metaphase I
anaphase I
telophase I
Meiosis is an important process that contributes to genetic variation in a population.
Fig. 4.1 shows a pair of homologous chromosomes during prophase I of meiosis.
Fig. 4.1
On Fig. 4.1, use the letter C with a label line to identify where crossing over occurs.
Yeasts are unicellular organisms from the kingdom Fungi. Saccharomyces cerevisiae is one species of yeast that can carry out either asexual reproduction by mitosis or sexual reproduction by meiosis.
Budding in S. cerevisiae is a process where a small daughter cell forms as a bud on the parent cell. The bud contains a copy of the parent cell nucleus and it eventually separates from the parent cell to form a new cell.
S. cerevisiae can exist in two forms: haploid cells or diploid cells.
- Haploid cells can be one of two different mating types: a and .
- Haploid cells can only mate with other haploid cells of the opposite mating type.
Key: (a) mating type a
Fig. 2.1
When there is a lack of nutrients, cells made in stage 3 will carry out stage 4 to make spores, which germinate only when conditions improve.
Suggest and explain how the type of reproduction that makes spores during stage 4 is advantageous for S. cerevisiae in a changing environment.
M. musculus produces gametes by meiosis. These gametes are genetically different.
There is random fusion of gametes at fertilisation.
Explain how the random fusion of gametes leads to the expression of rare, recessive alleles.