Chromosomes. Levels of chromatin organization. Human karyotype and its medical importance

Август 11, 2022

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Биология
Chromosomes. Levels of chromatin organization. Human karyotype and its medical importance

Содержание

2. MORPHOLOGY OF CHROMOSOMES: CHROMOSOMES ARE THE ROD-SHAPED ,FILAMENTOUS BODIES PRESENT IN THE NUCLEUS, WHICH BECOME VISIBLE
3. HOMOLOGOUS CHROMOSOMES ARE CHROMOSOMES THAT SHARE: THE SAME STRUCTURAL FEATURES (E.G. SAME SIZE, SAME BANDING PATTERNS,
4. DIPLOID IS A CELL OR ORGANISM THAT HAS PAIRED CHROMOSOMES, ONE FROM EACH PARENT. IN HUMANS,
5. AN AUTOSOME IS ANY OF THE NUMBERED CHROMOSOMES, AS OPPOSED TO THE SEX CHROMOSOMES. HUMANS HAVE
6. EACH CHROMOSOME IN ITS NON-REPLICATED STATE CONSISTS OF A SINGLE CHROMATID, WHICH IS SIMPLY A VERY
7. CENTROMERES WERE FIRST DESCRIBED BY WALTHER FLEMMING IN 1882. ALTHOUGH THE WORD “CENTROMERE” IS DERIVED FROM
8. THE CHEMICAL COMPOSITION OF A CHROMOSOME IS DNA AND HISTONE PROTEINS. THE DNA MOLECULES ARE VERY
9. POLYTENE CHROMOSOMES ARE LARGE CHROMOSOMES WHICH HAVE THOUSANDS OF DNA STRANDS. THEY PROVIDE A HIGH LEVEL
10. THE 22 AUTOSOMES ARE NUMBERED BY SIZE. THE OTHER TWO CHROMOSOMES, X AND Y, ARE THE
11. THE TERM KARYOTYPE REFERS TO A DISPLAY OF THE CHROMOSOMES OF A CELL BY LINING THEM
12. A CONDENSED MASS OF CHROMATIN THAT IS OBSERVED IN THE NUCLEUS OF NONDIVIDING SOMATIC CELLS OF
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Слайд 2

MORPHOLOGY OF CHROMOSOMES: CHROMOSOMES ARE THE ROD-SHAPED ,FILAMENTOUS BODIES PRESENT IN

THE NUCLEUS, WHICH BECOME VISIBLE DURING CELL DIVISION. THEY ARE CARRIERS OF THE GENE OR UNIT OF HEREDITY.

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HOMOLOGOUS CHROMOSOMES ARE CHROMOSOMES THAT SHARE: THE SAME STRUCTURAL FEATURES (E.G. SAME

SIZE, SAME BANDING PATTERNS, SAME CENTROMERE POSITIONS) THE SAME GENES AT THE SAME LOCI POSITIONS (WHILE THE GENES ARE THE SAME, ALLELES MAY BE DIFFERENT)

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DIPLOID IS A CELL OR ORGANISM THAT HAS PAIRED CHROMOSOMES, ONE

FROM EACH PARENT. IN HUMANS, CELLS OTHER THAN HUMAN SEX CELLS, ARE DIPLOID AND HAVE 23 PAIRS OF CHROMOSOMES. HUMAN SEX CELLS (EGG AND SPERM CELLS) CONTAIN A SINGLE SET OF CHROMOSOMES AND ARE KNOWN AS HAPLOID.

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AN AUTOSOME IS ANY OF THE NUMBERED CHROMOSOMES, AS OPPOSED TO

THE SEX CHROMOSOMES. HUMANS HAVE 22 PAIRS OF AUTOSOMES AND ONE PAIR OF SEX CHROMOSOMES (THE X AND Y). AUTOSOMES ARE NUMBERED ROUGHLY IN RELATION TO THEIR SIZES.

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EACH CHROMOSOME IN ITS NON-REPLICATED STATE CONSISTS OF A SINGLE CHROMATID, WHICH

IS SIMPLY A VERY LONG DNA MOLECULE TO WHICH ARE ATTACHED A GREAT MANY HISTONE PROTEIN MOLECULE COMPLEXES.

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CENTROMERES WERE FIRST DESCRIBED BY WALTHER FLEMMING IN 1882. ALTHOUGH THE

WORD “CENTROMERE” IS DERIVED FROM THE GREEK WORDS “CENTRO” (CENTRAL) AND “MERE” (PART), CENTROMERES ARE NOT ALWAYS FOUND IN THE CENTER OF CHROMOSOMES.

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THE CHEMICAL COMPOSITION OF A CHROMOSOME IS DNA AND HISTONE PROTEINS.

THE DNA MOLECULES ARE VERY LONG, YET THEY ARE PACKED WITH THE HELP OF POSITIVELY CHARGED HISTONES INTO A SMALLER DIAMETER. HISTONES ARE RICH IN ARGININE AND LYSINE (AMINO ACID RESIDUES), WHICH FORM THE CORE AROUND WHICH A DOUBLE-STRANDED DNA FRAGMENT IS WOUNDED.

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POLYTENE CHROMOSOMES ARE LARGE CHROMOSOMES WHICH HAVE THOUSANDS OF DNA STRANDS.

THEY PROVIDE A HIGH LEVEL OF FUNCTION IN CERTAIN TISSUES SUCH AS SALIVARY GLANDS OF INSECTS.

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THE 22 AUTOSOMES ARE NUMBERED BY SIZE. THE OTHER TWO CHROMOSOMES,

X AND Y, ARE THE SEX CHROMOSOMES. THIS PICTURE OF THE HUMAN CHROMOSOMES LINED UP IN PAIRS IS CALLED A KARYOTYPE.

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THE TERM KARYOTYPE REFERS TO A DISPLAY OF THE CHROMOSOMES OF

A CELL BY LINING THEM UP, BEGINNING WITH THE LARGEST CHROMOSOME AND WITH THE SHORT ARM ORIENTED TOWARD THE TOP.

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A CONDENSED MASS OF CHROMATIN THAT IS OBSERVED IN THE NUCLEUS

OF NONDIVIDING SOMATIC CELLS OF FEMALES. IT IS NOT OBSERVED IN THE SOMATIC CELLS OF NORMAL MALES. THE SUBSTANCE REPRESENTS MATERIAL WITHIN THE X CHROMOSOME THAT IS NOT INVOLVED IN SOMATIC-CELL METABOLISM. THE PRESENCE OF SEX CHROMATIN IN SOMATIC CELLS IS GENERALLY REGARDED AS PROOF OF THE SEXUAL IDENTITY OF FEMALES. ALSO CALLED BARR BODY.