Numerical Chromosmal Abnormalities Flashcards
When phase of meiosis does recombination (crossing over) occur?
prophase I
what is crossing over?
genetic material between homologous chromosomes is exchanged ensuring that no 2 chromosomes are the same, contributes to genetic variability
what occurs during anaphase I in regards to paternal and maternal chromosomes?
homologous chromosomes sort independently and maternal and paternal chromosomes are sorted into random combinations
what are the 2 events in meiosis that cause genetic variability among offspring?
- crossing over
2. segregation of chromosomes paternal and maternal
what is the difference in the end result of meiosis and mitosis?
meiosis: 4 haploid cells different
mitosis: 2 diploid cells identical
what is non-disjunction?
chromosome fail to segregate properly
what has to be formed for recombination to be performed?
synaptonemal complex
what is the remnant structure between homologous chromosomes after the synaptonemal complex breaks down?
chiasmata
where on chromosomes do non-disjunction events usually occur?
chiasmata
what does crossing over far from centromeres cause in meiosis?
causes spindle attachments and segregation during meiosis I to be less effective
what does crossing over too close to centromeres or having too many chiasmata cause?
homologs become entangled
what percentage of cells that have non-disjunction in meiosis I will be abnormal?
100%
what percentage of cells that have non-disjunction in meiosis II will be abnormal?
50%
what is the first number in karyotypic designations?
total number of chromomes
how are extra chromosomes added when writing a karyotype?
write +(chromosome number) at the end
ex trisomy 21 (47; XX +21)
