Meiosis and Chromosome Abnormalities Flashcards
What is the process of Meiosis? (PMAT-PMAT)
- Prophase 1
- Metaphase 1
- Anaphase 1
- Telophase 1
- Prophase 2
- Metaphase 2
- Anaphase 2
- Telophase 2
Description of the first PMAT
- Almost same as mitosis
- Non-sister chromatids touch at points called chiasmata
- Crossing over and recombination occurs
- This results in variation
Description of second PMAT
- Similar to first but DNA is not copied or crossed over
- Results in 4 haploid cells
How many sperm cells are formed per meiotic cycle?
4
How long does the meiotic cycle to produce the 4 sperm cells take?
60 days
Why do more mutations occur in spermatogenesis than oogenesis?
Sperm undergo far more divisions that ova so there is a greater mutation chance
What does each meiotic division of an ova produce?
- 1 ovum
- 3 polar bodies
What do these polar bodies become later in life?
Ova
When does spermatogenesis begin?
Puberty
When does oogenesis begin?
Early embryonic life
What does non disjunction mean?
- Sister chromatids don’t split during meiosis
- Results in both of them being present in one gamete
What is caused by trisomy 21?
Down’s Syndrome
What are some common characteristics of down syndrome?
- Facial characteristic
- IQ less than 50
What % of down syndrome, Patau syndrome and Edward’s syndrome is caused by non disjunction
90%
What is caused by trisomy 13?
Patau Syndrome
