Recent Problems in Evolution - 1991

Table of Contents

Diversity of heterochromatin banding patterns in eukaryotic Threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.chromosomes excludes any form of evolutionary descent

The heterochromatin in eukaryotic Threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.chromosomes exhibits specific banding patterns. A recent study performed quantitative analysis of the alterations of constitutive heterochromatin in eukaryotic Threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.chromosomes using the accumulated C-banding data. The study found that eukaryotes could be classified into two types by their C-banding patterns: 1) Type I included mammals, fish, and ants, and 2) Type II included amphibians, grasshoppers, and plants. C-bands were rather scarce in Type I eukaryote Threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.chromosomes and were found around the pericentromeric region when present at all, whereas the predominance of interstitial or terminal C-bands was found in Type II eukaryote Threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.chromosomes. The diversity of eukaryotes expressing different banding patterns (especially the divergence of ants and grasshoppers, while amphibians and plants exhibit the same banding patterns) seems to exclude the heterochromatins from any sort of evolutionary descent. (Imai HT. Idengaku Zasshi - Japanese Journal of Genetics 66 (5): 635-61, 1991.)

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Simultaneous evolution of receptors, ligands, and down-regulatory pathways?

There are numerous problems in the structural-functional organization, and of the origin and evolution of the chemosignal systems which realize the effect of hormones and hormone-like substances in the higher eukaryotes-lower eukaryotes-prokaryotes series. Simultaneous evolution of receptors, ligands, and down-regulatory pathways presents a major problem in terms of a reasonable mechanism. (Pertseva MN. Neuroscience & Behavioral Physiology 21 (6): 559-68, 1991.)

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Evolution of "complex" or composite morphological structures

How "complex" or composite morphological structures like the mammalian craniomandibular region can arise during evolution is a major unresolved problem. (Atchley WR. and Hall BK. Biological Reviews of the Cambridge Philosophical Society 66 (2): 101-57, 1991.)

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Structural and functional similarities in avian and mammalian brains evolved separately during a few million years?

Comparative morphology of mammals and birds, by 1) allometric studies of brain weight and brain structure volume in relation to body weight in mammals and birds; 2) architectonic studies using image analysis on cell and fiber stains as well as on histochemical preparations and receptor autoradiography; and 3) hodological studies with injections of [3H]-leucine, HRP and WGA-HRP reveal a vast amount of structural and functional similarities in avian and mammalian brain organization, especially an expansion of structures that permit multimodal integration capacity in the telencephalon. Evolutionists suggest that parallel evolution has occurred in these two groups of vertebrates. That these extremely complex structures would have evolved separately during a few million years is very unlikely, given that this sort of evolution did not occur even once during the long rein of the reptiles. (Rehkamper G. and Zilles K. Parallel evolution in mammalian and avian brains: comparative cytoarchitectonic and cytochemical analysis. Cell & Tissue Research 263 (1): 3-28, 1991.)

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Recent or ancient evolution of Noncoding sequences of DNA that are initially copied into RNA but are cut out of the final RNA transcript.introns?

Studies have shown that Noncoding sequences of DNA that are initially copied into RNA but are cut out of the final RNA transcript.introns are highly restricted in their phylogenetic distribution in eukaryotes, which evolutionists cite as evidence that Noncoding sequences of DNA that are initially copied into RNA but are cut out of the final RNA transcript.intronswere inserted late in eukaryotic evolution. (Palmer JD. Logsdon J.M. Jr. The recent origins of Noncoding sequences of DNA that are initially copied into RNA but are cut out of the final RNA transcript.introns. Current Opinion in Genetics & Development. 1 (4): 470-7, 1991.) However, other studies have shown that self-splicing Noncoding sequences of DNA that are initially copied into RNA but are cut out of the final RNA transcript.introns are found in cyanobacteria, which are prokaryotes that have been hypothesized to be the ancestor of all living things. (Shub DA. The antiquity of group I Noncoding sequences of DNA that are initially copied into RNA but are cut out of the final RNA transcript.introns. Current Opinion in Genetics & Development 1 (4): 478-84, 1991.)

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Co-evolution nuclear- Of or referring to the mitochondria, the organelles that generate energy for the cell.mitochondrial genomes is unlikely

Mitochondria possess a small set of genes that are essential for respiratory function. The vast majority of Of or referring to the mitochondria, the organelles that generate energy for the cell.mitochondrial structural and enzymatic components are coded by nuclear genes. Mitochondria are hypothesized to have descended from prokaryotic parasitism of eukaryotic cells. However, there is a remarkable diversity among eukaryotic lineages and an impressive complexity of events needed to achieve nuclear- Of or referring to the mitochondria, the organelles that generate energy for the cell.mitochondrial harmony. (Bonen L. The Of or referring to the mitochondria, the organelles that generate energy for the cell.mitochondrialgenome: so simple yet so complex. Current Opinion in Genetics & Development 1 (4): 515-22, 1991.)

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Neutral genetic changes have predominated over Darwinian evolutionary changes

In sharp contrast to the Darwinian theory of evolution by natural selection, the neutral theory claims that the overwhelming majority of evolutionary changes at the molecular level are caused by random fixation (due to random sampling drift in finite populations) of selectively neutral (i.e., selectively equivalent) mutants under continued inputs of Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations. The theory also asserts that most of the genetic variability within species at the molecular level (such as An organic compound made of amino acids arranged in a linear chain, joined together by peptide bonds between the carboxyl and amino groups of the adjacent amino acid residues.protein and Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA A common variation in the sequence of DNA among individuals of a species or race.polymorphism) are selectively neutral or very nearly neutral and that they are maintained in the species by the balance between Relating to a permanent structural alteration in DNA, consisting of either a substitution, insertion or deletion of nucleotide bases.mutationalinput and random extinction. The recent accumulation of Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA sequence data has greatly strengthened this theory. In fact, the evidence conclusively shows that since the origin of life on Earth, neutral evolutionary changes have predominated over Darwinian evolutionary changes. (Kimura M. The neutral theory of molecular evolution: a review of recent evidence. Idengaku Zasshi - Japanese Journal of Genetics 66 (4): 367-86, 1991.)

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