Gene And Chromosomes
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Transcript of Gene And Chromosomes
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DNA ORGANIZATION IN CHROMOSOME
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Key vocabulary Nucleoid/ nucleosomeNucleoid/ nucleosome Chromatin Chromatin Scaffold proteinScaffold protein Histone/ non histoneHistone/ non histone CentromereCentromere TelomereTelomere KaryotypingKaryotyping
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Organization Highly dependent on the type of org.Highly dependent on the type of org. Prokaryotic vs Eukaryotic org.Prokaryotic vs Eukaryotic org. Different technique used to visualise.Different technique used to visualise.
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Precise location
Such a compact space. Question arises on how key activities in Such a compact space. Question arises on how key activities in protein synthesis can take place within this limited space.protein synthesis can take place within this limited space.
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Closer view..
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ChromatinChromosome discovered by W. Waldeyer.Euchromatin –Fibers less packed, disperse –Fibers less packed, disperse
appearance occupying most of the nuclear appearance occupying most of the nuclear region.region.
Heterochromatin- More dense area, found at More dense area, found at centromeres.centromeres.
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Chromosome number.Diff. org = diff. no. Man 23 pairs =Total 46. 22 pairs of autosomes 2 sex chromosomes. Cht. size shape + pattern, Numbered in order of size.Different cell diff number eg.
Liver cells 92.
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Varies among species.Varies among species. Unrelated to the size or biological complexity Unrelated to the size or biological complexity
of an org.of an org. An asian deer = 3.An asian deer = 3. Diploid – 2 of the chromosome in a set.Diploid – 2 of the chromosome in a set. Tetraploid – 4 of each chr.Tetraploid – 4 of each chr. Octaploid – 8 of each chr.Octaploid – 8 of each chr.
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G-bands
Certain Tx/ staining techniques (Eg. Giemsa) Certain Tx/ staining techniques (Eg. Giemsa) will allow chromosomes to have striations.will allow chromosomes to have striations.
Large structures containing approx 10Large structures containing approx 107 7 bp bp DNADNA
chromosomes can be id by cht. banding chromosomes can be id by cht. banding pattern- Used for karyotyping – pattern- Used for karyotyping –
Translocations can be id. by comparing to the Translocations can be id. by comparing to the original diploid set.original diploid set.
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Homologous pairs..Homologous pairs..
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Homologous contd.. Notice that the size,
order of bands, and shape is the same for both chromosomes.
Carry the same genes in the same order.
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Human chromosomes..
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Human Karyotype
Sex chromosomes
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Chromosomes and genes..
The dark lines represent bands.
Each chromosome, bears a particular set of genes, these genes are arranged in a specific order.
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Typical metaphase chromosome
i.i. Contains a DNA replication origin ii. A centromere to attach the DNA to the mitotic
spindle. iii. A telomere located at the end. DNA needs to be condensed. Chromosomes with AT/ GC base pair specific dyes. When
stained. Mitotic chromosomes have a banded structure
. ? Methaphase and not other stages?
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Basic units of a chromosome i. i. DNA (2.2m = Massive folding + coiling) ii. Proteins (Histones, scaffold p, polymerase) iii.Small amounts of RNA.
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Complex between histones + DNA = chromatin. Nucleosome = basic structure of chromatin (beaded appearance) Scaffold protein = non-histone p. Nucleosome coils aound it. Polymerases = enzymes involved with
a)transcription of the gen. information during protein synthesis b)replication of the DNA prior to the division of chromosomes.
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Nucleosome.. Contains 200 bp DNA.Contains 200 bp DNA. Subunit of chromatin Subunit of chromatin
composed of short DNA composed of short DNA wrapped around histonewrapped around histone
8 histone molecules = 8 histone molecules = octamer.octamer.
Nucleosome fibre is tightly Nucleosome fibre is tightly coiled and looped around coiled and looped around non-histone proteinsnon-histone proteins
Nucleosomes are packed Nucleosomes are packed together = compact.together = compact.
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Placement of genes Gene = A region of DNA Gene = A region of DNA
that that controls hereditary info specifiying the sequence of a particular protein. .
Carries biological info Carries biological info that must be copied and that must be copied and transmitted to its transmitted to its progeny.progeny.
Can be as short/long.Can be as short/long. 2001: 30,00/40,000 2001: 30,00/40,000
genes.genes.
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Color BlindnessColor Blindness Muscular DystrophyMuscular Dystrophy Fragile X syndromeFragile X syndrome HemophiliaHemophilia