Numerical Chromosomal abnormalities Flashcards
What is metacentric and which chromosomes are metacentric
p & q arms are even length
1-3 and 16-18
What is submetacentric and which chromosomes are submetacentric
p arm shorter than q arm
4-12, 19-20 and X
What is acrocentric and which chromosomes are acrocentric
long q, very small p
p contains no unique DNA
13-15, 21-22 and Y
what does haploid mean
one et of chromosome (n=23) as in a normal gamete
what does diploid mean
cell contains 2 sets of chromosome (2n= 46) as in normal in human
what does polyploid mean
multiple of the haploid number (4n=92)
what does Aneuploid mean
Chromosome number which is not an exact multiple of haploid number- due to extra or missing chromosome
what is name given to the primary mechanism by which aneuploidy arise
non-disjunction
when does recombination occur
during metaphase 1
how does recombination occur
the 2 pairs of chromosomes are stuck together by synaptonemal complex which enables physical exchange of genetic material , they cross over and form a structure known as chiasma
what are the 3 common autosomal aneuploidies
trisomy 13( patau's) trisomy 18 (edwards) trisomy 21 ( down's)
4 common sex chromosome aneuploidies
turners (45, X)
Triple X syndrome (47, XXX)
Klinefelter’s (47,XXY)
47,XYY)
what does mosaicism mean
the presence of 2 or more genetically different cell lines derived from a single zygote
meiosis I
align as 23 bivalent
allows for chiasma formation
pulls apart homologues form one another
daughter cells have 23 chromosomes each with 2 chromatids
meiosis II
align as independent chromosomes
sister chromatids pulled apart
daughter cells have 23 chromosome (each of 1 chromatid )
