Lecture 4 Flashcards
DNa+ histones is
In the form of
Chromatin
Beads on a thread
1st order packaging
Nucleosomes of a histones octamer
H2A, H2B, H3, H4
2 copies of each
10 nm diameter
1.65 around histones
Why DNA loops around histones
As it is -vely charged due to phosphate groups while histones are positively charged
2nd and 3rd packaging order
Solenoid fibers, 6 nucleosomes 30nm diameter
Scaffold loops the chromosomes
What is chromosomal aberrations
Leads to
A change in number or structure of chromosomes
Death/mental retardation/genetic abnormalities/ infertility/spontaneous abortions
Number abnormalities
Aneuploidy only. Chromosome is the difference, 47, 45
Polyploidy whole set of chromosomes replicated
Aneuploidy is sometimes related to
Found in
It is… except
Age
Oocytes and early embryos (trisomies and monosomies)
Lethal, down syndrome and sex chromosomes
Some syndromes
10
Cri du chat
Patau
Down
Edward
Jacobson
Klinfelter
turner
Triple
Triple
Wolf hirschhorn
Cri du chat»_space;del 5p
Patau» trisomy 13
Down»trisomy 21
Edward»_space;trisomy 18
Jacobson» terminal 11q del
Klinfelter»_space; XXY
turner» X0
Triple xxx
Triple YYY
Wolf hirschhorn»_space; partial del of 4p
Cri du chat, deletion symptoms
Cat like cry disappears with age
Severe mental retardation
congenital heart disease
low birth weight
poor growth
behavioral issues
Hypertelorism widely separated eyes
Inversion
180 reverse in a chromosome segment by breaking and reassociation
Paracentric , centromere not involved
Pericentric, centromere involved
A disease due to translocation
Burkitts lymphoma
Aggressive lymphoma affecting b lymphocyted
Translocation
A piece of chromosome breaking off and joining another one.
Balanced/reciprocal»_space; no loss or gain
Unbalanced/ nonreciprocal» loss and gain
Isochromosomes
1 arm is missing and the other arm id duplicated by centromere dividing transversely instead on longitudinally
2 copies of p arm or q arm
Disease due to isochromosome
Turner syndrome
Ring chromosme
Loss of both ends causing rejoining as a circle very rare