What are spindle fibres?
Microtubules
What do spindle fibres attach to on the centromere?
Kinetochore
What are the two arms of a chromosome?
P arm (short) and Q arm (long)
What are non-sister chromatids?
Have the same genes but may have different alleles (chromatids on homologous pairs)
What are the four arrangements of centromeres?
Metacentric
Submetacentric
Acrocentric
Telocentric (not present in humans)
When does crossing over occur in meiosis?
Meiosis 1 - between prophase 1 and metaphase 1
Another name for crossing over of chromatids…
Chiastama
What two things lead to genetic variation in germ line cells?
- Independent segregation of homologous pairs
2. Crossing over of chromatids
Can non-disjunction occur in mitosis and meiosis?
Yes
What does non-disjunction lead to?
Aneuploidy (triosomy/monosomy)
What is karyotyping?
Chromosome analysis
In meiotic non-disjunction what cells are produced before fertilisation?
Meiosis 1 - 2x double chromosomes, 2x no chromosome
Meiosis 2 - 2x normal, 1x double chromatids 1x no chromatid
In meiotic non-disjunction what cells are produced after fertilisation?
Meiosis 1 - 2x triosomy, 2x monosomy
Meiosis 2 - 1x triosomy, 1x monosomy, 2x normal
What is stage G0 of the cell cycle?
Cells that don’t go back into the cell cycle go into this stage (either forever or temporarily) e.g. nerve cells forever
What is a non-mosaic karyotype?
If non-disjunction happens in the first post-zygotes division of mitosis this occurs
What is a mosaic karyotype?
If non-disjunction happens in later cell division (mitosis) this occurs
What happens in subsequent cell divisions if a cell is monosomy?
The cell line is usually lost unless it is on the x-chromosome
How long does oogenesis take?
12-50 years
How long does spermatogenesis take?
60 days
What does oogenesis produce?
One mature ovum and 3 polar bodies
What does spermatogenesis produce?
4 sperm cells
