A diploid cell has 12 chromosomes. In the standard model, how many are in a haploid gamete?
Answer and explanation
6
Half of 12 is 6.
Subjects
Genetics & inheritance
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Sample exercises
What separates in meiosis I in the standard model?
- Only cell-wall layers.
- All sister chromatids in the same way as meiosis II.
- Homologous chromosomes.
Answer and explanation
Homologous chromosomes.
The first division separates homologous pairs.
How many DNA replications precede the two meiotic divisions in the usual model?
- None.
- One.
- Two separate replications, one before each division.
Answer and explanation
One.
DNA replication occurs once before meiosis I.
Two gametes each have 5 chromosomes. What chromosome number follows their fusion in the model?
Answer and explanation
10
5 + 5 = 10.
Why are the products of meiosis not generally genetically identical?
Answer and explanation
Recombination and chromosome assortment can distribute different allele combinations.
Mention at least one valid variation mechanism.
In meiosis II, what usually separates?
- Homologous species.
- Sister chromatids.
- Only all mitochondria.
Answer and explanation
Sister chromatids.
The second division separates sister chromatids.
Study notes
Meiosis and chromosome sets
Track sets of chromosomes rather than assuming gametes are identical.
Grades 9–12Meiosis and chromosome sets · Revision sheet
Track sets of chromosomes rather than assuming gametes are identical.
Grades 9–12DNA structure and complementary sequences
Keep bases, strands and genes distinct.
Grades 8–11DNA structure and complementary sequences · Revision sheet
Keep bases, strands and genes distinct.
Grades 8–11From genes to proteins
Use transcription and translation as distinct processes.
Grades 10–12From genes to proteins · Revision sheet
Use transcription and translation as distinct processes.
Grades 10–12Single-gene inheritance models
Treat dominant as an expression rule, not a claim of superiority.
Grades 9–12Single-gene inheritance models · Revision sheet
Treat dominant as an expression rule, not a claim of superiority.
Grades 9–12Variation beyond simple dominance
Recognize incomplete dominance, codominance and polygenic traits.
Grades 10–12Variation beyond simple dominance · Revision sheet
Recognize incomplete dominance, codominance and polygenic traits.
Grades 10–12DNA base-percentage model
In the stated double-stranded DNA model, A = T and C = G; all four percentages sum to 100.
Grades 9–12Diploid to haploid
In the stated standard model, meiosis reduces two chromosome sets to one. Do not substitute a universal species count.
Grades 9–12Expected counts in Aa × Aa
For the simple Aa × Aa model, P(aa) = 1/4. An expected count is not a guaranteed outcome in a finite sample.
Grades 9–12Genetics & inheritance · Formula reference
Formula reference
Grades 9–12