cytogenetics Flashcards
what is cytogenetics? and why is it important?
is the study of chromosomes. and is important in the diagnosis of genetic syndromes.
what needs to be happening for chromosomes to be visualised?
the cells need to be dividing
what is used to stain chromosomes? and how does it work?
giemsa. works by specificity for dna phosphate groups
what is meiosis?
meiosis is cell division to produce haploid gametes from diploid cells.
what are the stages of meiosis?
prophase, metaphase, anaphase and telophase. each phase has stage one and stage two. In stage one homologous chromosomes (in the form of sister chromatids) separate. in stage two sister chromatids separate.
how does meiosis generate diversity?
- random assortment of chrom paris
- recombination (cross over events)
recombination?
cross over events between homologous (maternal and paternal) chromosomes. occurs at structures called chiasmata.
female meiotic cycle stages?
prophase (crossing over) occurs in 1st trimester. dicytyate arrest (homos remain paired by crossover) occurs in 2nd trimester. then birth. then puberty oocytes released once a month.
aneuploidy?
org has 1 or few chroms added or reduced
trisomy?
type of aneuploidy in which there are 3 chroms instead of 2
does abnormal sex chromosome number have less of an effect than change in autosome number? and why?
less of an effect. because y has very few genes. so an extra or less y has limited effect.
syndromes due to change in sex chroms
turner in f. klinefelter in m.
why does trisomy 21 usually occur?
due to an error in meiosis 1 where chroms don’t separate
characteristics of downs syndrome?
cognitive impairment (low iq) facial expression some have heart defect and leukaemia also association with alzheimer's.
microdeletion syndrome?
syndrome caused by small deletion in chromosome. not able to be screened by karyogram. detected by molecular techniques. arises due to unequal crossing over during recombination (mismatch).
