Studied by 0 people
prokaryotic chromosomes - types
single circular chromosome (naked) in nucleoid region
bacterial chromosome
circular plasmids
supercoiling: to compact into the cell
eykaryotic chromosomes - histones
multiple linear chromosomes
histones = globular proteins that dna wraps around → nucleosome
linker dna in bw nucleosomes
histone octamer: group of 7 histones
autoradiography
used to est the length of dna molecules in chromosomes
\depends on the emission of radioactive particles
sex determining region y
sry gene
expression initiates testicular dev
absence means default → female
haploid vs diploid
1 vs 2 complete sets of chromosomes
diploid: 1 set from father and mother each
karyographs
the arrangement of chroms according to their no., size, structure etc.
preparation:
take a sample of cells, centrifuge, undergo cell division, use dye to cause banding pattern, take photo using microscope, arrange.
human sex
female XX
male XY
X is bigger
down syndrome
trisomy 21 - extra chrom 21.
1st test: non-invasive nuchal translucency scan at 11-13 weeks. large amt of nuchal fluid associated w down syndrome
next: amniocentesis — get sample of amniotic fluid, prepare karyotype to determine. 16th week. ~1% miscarriage.
OR chorionic villus sampling — take sample of cells. 11th week. ~2% miscarriage.
syndromes
klinefelter syndrome — extra chrom 23 in a man (XXY)
turner syndrome — monosomy x (XO)
