GIM 6 - chromosomal basis of inheritance Flashcards
what is cytogenetics
study of chromosomes
what is autosomes
chromosome 1-22
23 = sex chromosomes
when is chromosome most visible?
in metaphase in mitosis
at what phases do G-banding test at ?
metaphase in mitosis
at what phases do molecular cytogenetic test at ?
all phases and stages
what does karyotype mean?
using G-banding and sort out from the largest chromosome to the smallest
what are the telomere
the endings of the chromosome bands
what are the 2 large subdivision for chromosome bands
P & Q
how many smaller subdivisions are there for the p band
2
how many smaller subdivisions are there for the q band
3
what are the different types of cytogenetic abnormality
numerical & structural
what does diploidy mean
2 copies of each chromosome
what does aneuploidy
gain (trisomy) or less (monosomy)
what does aneuploidy
gain whole sets (triploidy or tetraploidy)
what does mosaicism mean
diploidy & aneuploidy
where can numerical abnormality arise
gametogenesis - meiosis, fertilisation, early cleavage
what can increase in maternal age do?
increase aneuploidy
how is meiotic error arise?
chromosome non-disjunction, chromatid non-disjunction
what syndrome can trisomy 18 lead to?
Edwards Syndrome
what are some clinical features for Edwards Syndrome
Head: microcephaly; low set ears; micrognathia; ears low set; cleft lip and palate
Hands & feet: Clenched hands, overlapping fingers; Rockerbottom feet
Severe mental retardation
what are some examples of organ malformation in trisomy 18
umbilical/inguinal hernia
congenital heart disease
congenital kidney abnormalities
what is the cause of patua syndrome
trisomy 13
what causes Turner’s syndrome
45,X
what causes Klinefelter’s syndrome
47,XXY
what are some clinical features for Turner’s Syndrome
Reproductive, Lymphatic, Skeletal abnormaliteis
how is Klinefelter Syndrome commonly presented
infertility & hypogonadism
what errors can arise in fertilisation?
polyploidy, molar pregnancy
what is molar pregnancy
double paternal, no maternal
what happens in double maternal genes instead of paternal and maternal
very small placenta - small baby
what happens in double paternal genes instead of paternal and maternal
huge placenta
what does maternal and paternal genome code for?
M - foetus
P - placenta
what problem can arise in early cleavage?
mosaicism
