Chromosome structure and function Flashcards
Leptotene
chromosomes condense
Zygotene
synaptonemal complex forms
Pachytene
crossing over occurs
Diplotene
homologs start to separate, but remain attached at chiasmata
Diakinesis
separation of homologs
Only if fertilized by sperm will ovulation proceed to
M2
Meiotic nondisjunction
most common mutation in man
Nondisjunction
when chromosomes don’t separate properly. can result in trisomy or monosomy
- can be mitotic or meiotic
Factors in maternal age effect
- decreased interactions b/t homologous chromosomes in prophase-1.
- long prophase 1 arrest in females
- Failed repair checkpoints in oocyte
Mechanisms of triploidy
dispermy
failure of meiotic division
Diandric
2 pat and 1 mat
Digynic
2 mat 1 pat
Alternate seg
normal and balanced
Adjacent seg
2 unbalanced forms
Adjacent 2 seg
products are rare and have 2 identical centromeres . Less viable
CNV can be identifies by
CMA
Robertonian translocation
translocation b/t 2 Afrocentric chromosomes = loss of short arms of both chromosomes, but does not affect DNA of long arms. Usually dicentric
Forms a trivalent configuration.
FISH advantages
“SINCR”
single cell level
inexpensive
no dividing cells
cryptic chromosomes arrangements
resolution
FISH limitations
not genome wide
cant identify point mutations
cant detect gain or loss of chromosome functions
Advantage of CMA
higher res than G-band
can detect tandem dups
doesn’t require dividing cells
Limits of CMA
cant detect the following :
point mut
balanced rearrangments
low level mosciasm
its expensive
