I ask for someone to explain a couple of things fo rme..?

Question

I have a test coming up soon for biology. I'm quite confused with some parts. Can some kind people help explain the following subjects:

A)The Genetic Equivalence of Differentiating Cells
B) DNA-RNA hydidization
C) Determination and Differentiation in cells (Possibly frog and snail)
D) Cytoplasmic Determination in cells
E) Cell-cell interactions

Explaining one of these topics will help me a lot!

Thanks.

Sorry for the many q's. Just got kinda carried away.

Answer 1

first don't ask 5 questions as one....
so here is the answer to B) DNA-RNA hydidization

Theory: Complementarity and Hybridization

Molecular searches use one of several forms of complementarity to identify the macromolecules of interest among a large number of other molecules. Complementarity is the sequence-specific or shape-specific molecular recognition that occurs when two molecules bind together. For example: the two strands of a DNA double-helix bind because they have complimentary sequences; also, an antibody binds to a region of a protein molecule because they have complimentary shapes.

Complementarity between a probe molecule and a target molecule can result in the formation of a probe-target complex. This complex can then be located if the probe molecules are tagged with radioactivity or an enzyme. The location of this complex can then be used to get information about the target molecule.

In solution, hybrid molecular complexes (usually called hybrids) of the following types can exist (other combinations are possible):

* 1) DNA-DNA. A single-stranded DNA (ssDNA) probe molecule can form a double-stranded, base-paired hybrid with a ssDNA target if the probe sequence is the reverse complement of the target sequence.

* 2) DNA-RNA. A single-stranded DNA (ssDNA) probe molecule can form a double-stranded, base-paired hybrid with an RNA (RNA is usually a single-strand) target if the probe sequence is the reverse complement of the target sequence.

* 3) Protein-Protein. An antibody probe molecule (antibodies are proteins) can form a complex with a target protein molecule if the antibody's antigen-binding site can bind to an epitope (small antigenic region) on the target protein. In this case, the hybrid is called an 'antigen-antibody complex' or 'complex' for short.

There are two important features of hybridization:

1) Hybridization reactions are specific - the probes will only bind to targets with complimentary sequence (or, in the case of antibodies, sites with the correct 3-d shape).

2) Hybridization reactions will occur in the presence of large quantities of molecules similar but not identical to the target. That is, a probe can find one molecule of target in a mixture of zillions of related but non-complementary molecules.

These properties allow you to use hybridization to perform a molecular search for one DNA molecule, or one RNA molecule, or one protein molecule in a complex mixture containing many similar molecules.

These techniques are necessary because a cell contains tens of thousands of genes, thousands of different mRNA species, and thousands of different proteins. When the cell is broken open to extract DNA, RNA, or protein, the result is a complex mixture of all the cell's DNA, RNA, or protein. It is impossible to study a specific gene, RNA, or protein in such a mixture with techniques that cannot discriminate on the basis of sequence or shape. Hybridization techniques allow you to pick out the molecule of interest from the complex mixture of cellular components and study it on its own.

Basic Definitions

Blots are named for the target molecule.

Southern Blot
DNA cut with restriction enzymes - probed with radioactive DNA.

Northern Blot
RNA - probed with radioactive DNA or RNA.

Western Blot
Protein - probed with radioactive or enzymatically-tagged antibodies.

Overview

The formation of hybrids in solution is of little experimental value - if you mix a solution of DNA with a solution of radioactive probe, you end up with just a radioactive solution. You cannot tell the hybrids from the non-hybridized molecules. For this reason, you must first physically separate the mixture of molecules to be probed on the basis of some convenient parameter.

These molecules must then be immobilized on a solid support, so that they will remain in position during probing and washing. The probe is then added, the non-specifically bound probe is removed, and the probe is detected. The place where the probe is detected corresponds to the location of the immobilized target molecule.

Answer 2

YEA! Gymnastics is a sport just like any other! I was a competitive gymnast for 11 years. I wouldn't recommend you aim for the Olympics, but gymnastics is a fun recreational activity for anyone! I coach gymnastics to girls (tumbling mostly for cheerleaders) in college! A lot of them couldn't even do a cartwheel so they started from scratch at 20. If they aren't too old neither is 16!