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From:
Subject: Re: [Melungeon] re Joanne re Brent re Spanish Cherokee and Silver Mines
Date: Tue, 4 Mar 2003 19:39:04 EST
In a message dated 3/4/2003 10:01:26 AM Pacific Standard Time,
writes:
> I'll restate it: the product of the combination of the parents' DNA within
> the nucleus of the single cell that starts the beginning of another human
> life is not yet understood to the point of saying how those new assortments
> happen (the recombining of DNA material from the parent male and female). I
> think it is common knowledge that genes from the father and genes from the
> mother combine to form a new human but what goes on in the nucleus of the
> cell to form these "assortments" is not understood
Hi Ya, Well it is pretty clear to me: :::
<A HREF="http://www.people.memphis.edu/~clessman/LECT2.htm">http://www.people.memphis.edu/~clessman/LECT2.htm</A>;
LECTURE 2Evolutionary considerations: An introductiondefinitions of
terms: 1) spiral vs radial cleavage (see overheads) 2)
protostomes vs deuterostomes 3) schizocoelus vs enterocoelus 4)
mosaic vs regulativeCellular differentiation - classic expts. in
nucleo cytoplasmic interaction - amoebae - acetabularia determine the effect
of nuclear removal or transplantation or give expression turn of the century
amoebae remove nucleus with glass needle cytoplasm contains many activities -
cytoplasmic streaking - pseudopodia - ingests food - but no digestion of food
- survives for several days but eventually dies - transplant back an amoebae
nucleus - division and growth of amoeba colonyAcetabularia single celled alga
cap stalk 3-5 cm nucleus all can be enucleated by cutting at lower portion
of stem yielding an anuclear fragment of stem and caps. This anuclear portion
is able to carry out photosynthesis and lives for weeks.Modern approaches to
study of nucleocytoplasm interaction. a. cell-cell fusion b.
karyoplast, cytoplast preps. c. microinjectionChick erythrocyte
(nucleus very condensed with little or no transcriptional activity) fully
differentiated (doomed to die without dividing) fuse with Hela cell as
heterokaryon chick erythrocyte nucleus - dispenses its chromatin - makes RNA
(transcription begins) - nucleolus forms (ribosome synthesis) - eventually
replicates DNA - nucleus swells and takes up human nucleus proteins from Hela
cells (developed an intense stain with fluorescent labeled antibodies
obtained from patients with Lupus erythematosus (produce antibodies to their
own nuclear proteins) - These proteins may be identical to x-some
decondensation factor . synthesis of nucleic acid is controlled by
cytoplasmic environment Cytoplast and Karyoplast - treat hela cells
with cytochalasin B after allowing to attach to plastic - centrifuge to cause
extrusion of nucleus - Karyoplast = nucleus with thin coat of cytoplasm -
cytoplast = a nuclear cytoplasm Hela - cytoplast + chick erythrocyte cell
fusion (sendai virus) activated erythrocyte nucleus . only cytoplasm needed
for nuclear activationCytoplasts live at least 2 days and phagocytose
materials, substrate attachment and cell movementConclusion indicate that
patterns of nucleic acid synthesis and gene expression by a nucleus can be
modified by substance in the cytoplasmMicroinjection oocyte (Xenopus, Rana)
If nuclei are transplanted into oocytes, the pattern of nucleic acid
synthesis resemble that of host cell. Molecular Mechanism of Cell
Differentiation - Diminution of DNA complement - In some organisms x-somes or
part of x-somes are lost during mitosis - Early embryologists felt that this
diminution occurred in all organisms and that this was the cause of cell
differentiation - However we now know that in most organisms the DNA content
of somatic cells is constant in all tissues (<A HREF="http://www.people.memphis.edu/~clessman/diminution.htm">diminution.htm</A>)J.B. Gurdon
finalized the proof that DNA was not lost by nuclear transplantation
expts.McKinnell - used marked nucleus Epithelial cells can be visualized on
surface of tadpole. 3n embryo has larger cells. Also kidney tubules
x-section. Larger Nuclei and cell volume: Nucleo cytoplasmic ratios are the
same for all three above.To make a clone: 1. take mature oocyte of some
species as donor, remove metaphase II spindle 2. microinject a nucleus from
donor (preferably a stem cell i.e., spermatogonium) 3. place in suitable
environmentVolpe + Illmensee - Jackson lab Bar Harbor, Maine - have cloned
mice - put "manufactured" embryo into surrogate mother (in utero)This brings
up subject of cloning Gurdon Oxford Briggs & King McKinnell DiBeradino Volpe
Subtelny Illmensee ? Bar Harbor (Peter Hoppe?) Jackson Laboratory Technical
damage vs. intrinsic change = differentiation 100 % normal Briggs & King
expt. development of recipient age of donor as donor (blastula) gets older
the cells get smaller (gastrula --adult) so technical difficulties of
manipulating small cells arise. perhaps mitotic rate is factor, blastula
cells have u mitotic rate than gastrula Other technical problems. -
enucleation--Briggs & King, remove metaphase spindle normally with
micromanipulator, difficult - Gordon - U.V. irradiation - McKinnell -
microbeam laser through microscope spot w 10 u wide pulse, coagulum produced
which include metaphase spindleEDTA (versene) chelater - causes dissocation
of blastula cells (gentler than trypsin dissoc)Blastula donor 1. mechanical
dissoc. 135 transfer - 7/larva 5% rate2. EDTA, 71 transfer - 25 larva 35%
rateGastrula donor 1. 20 - 4 larva 20% rate2. 18 - 2 larva 11% rate EDTA not
as good for gastula nucleiMeiosis - two divisions - only occurs in germ
cells, giving rise to gametes or sex cells Division I <A HREF="http://www.people.memphis.edu/~clessman/Human%20Meiosis.htm">Human Meiosis.htm</A>
Prophase I = Preleptonema Leptonema Zygonema Pachynema Diplonema Diakinesis
Prometaphase I Metaphase I Anaphase I Telophase I Interphase (no S
phase) (no growth) Division II Prophase II Metaphase II Anaphase II
Telophase IIStart with primary oocyte or primary spermatocyte.Preleptonema -
early prophase, x-somes difficult to seeLeptonema 1. DNA replication has
occurred but x-somes look single not double 2. Show bead-like thickenings
(chromosomes)Zygomena - 1. Synapsis of homologous x-somes - formation of
synaptonemal complex - protein structure pairing up of homologous x-somes
based on complementary nucleic acid basesPachynema - pairs of homologous
chromosomes act as a unit - during this stage that homologous exchange
segments (or recombine) Diplomena - the synaptonemal complex disappears
synaptonemal complex . function to 1) stabilize synapsis 2) recombination -
homologs actually move apart partially at this stage but remain joined at
chiasma which are believed to be areas of crossing over or recombination -
long lasting period. human oocyte = 40 year fish, amphib. <A HREF="http://www.people.memphis.edu/~clessman/The%20Reinitiation%20of%20Meiosis%20in%20Mammals.htm">The Reinitiation
of Meiosis in Mammals.htm</A>, reptile and bird have extreme uncoiling of x-somes
- sometimes forming "lampbrush" chromosomes. These are related to intense RNA
synthesis.Diakinesis - x-some begin condensing - nucleoli disappear - chiasma
disappear - x-somes homologs held together only at their endsSome species
(i.e., starfish) are in arrested diakinesis until fertilized by sperm then
meiosis proceeds.Prometaphase I - x-some condensation maximum - nucleus
envelope breakdown - each homologue becomes attached by its centromere to a
spindle fiberMetaphase I - x-somes on equatorial plate. - some species
(insects) oocytes are inseminated at this stage (arrested at Meta I until
fertilization)Anaphase I - homologues move to respective poles - centromeres
do not breakTelophase I - cessation of x-some movement - decondensation -
result in oocyte + polar body I (secondary oocyte) or (spermatocyte
secondary)Interphase - no DNA replication.Prophase II - short - x-somes
condenseMetaphase II - x-somes on equitorial plate - in some species (i.e.,
fish, frog, humans) arrested at Metaphase II until fertilized Anaphase II -
centromere breaksTelephase II - result in egg + polar body II and
(spermatozoa)
Kelly Pritchard
Isla Vista, California
http://melungeon_music.tripod.com/melungeonmusic/
<A HREF="http://melungeon_music.tripod.com/melungeonmusic/">Melungeon Music</A>
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