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13 Cards in this Set
- Front
- Back
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prokaryotic vs eukaryotic chromosomes |
PROKARYOTE -bacterial genomes consist of a single circular DNA molecule -circular DNA is complexed to proteins - helps with compaction/packaging -forms small/supercoiled twisted loops -topoisomerase: enzyme that relieves supercoiling prior to replication and transcription EUKARYOTE -each cell has multiple chromosomes and much more DNA than bacteria -no relationship between the number of chromosomes and organism complexity |
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eukaryotic DNA sequences |
-3 types: 1. unique sequence DNA 2. moderately repetitive DNA 3. highly repetitive DNA |
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unique sequence DNA*** |
-protein-coding sequences -usually present only once in a genome?? -gene families: unique DNA genes with several similar copies that arose from duplication?? |
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moderately repetitive DNA*** |
-repeated thousands of times -some functions (rRNA, tRNA) but most have no known function -2 types: 1. tandem repeats: appear one after the other, clustered at a few locations 2. interspersed repeats: scattered throughout the genome, most act as transposable elements?? -SINES: short interspersed elements -LINES: long interspersed elements |
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highly repetitive DNA*** |
-satellite DNA: highly repetitive?? -differs in density from main-based DNA (%G/C vs A/T) -short sequences repeated many times -associated with heterochromatic regions:?? 1. telomere sequences: highly conserved, maintain integrity of chromosomes?? 2. centromere sequences: spindle fiber binding, not conserved between higher organisms?? |
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eukaryotic chromosomes |
-larger in size than prokaryotic so require more packaging/folding -chromatin: associated with proteins -2 types of chromatin: 1. euchromatin: decondensed areas - we think includes more of the genes 2. heterochromatin: areas that remain condensed - contain non-coding DNA (no genes), centromere/telomere regions, long sequences of tandem repeats |
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chromatin structure |
-nucleosome: DNA complexed with proteins -histones: most abundant proteins - positive charge of histones attract negatively charged DNA -nucleosomes wrap around themselves to produce tightly condensed fibers -fibers are compressed to produce the chromatin of a chromosome |
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chromosomes structure |
-telomere: ends of chromosomes, enhance stability -centromere: primary constriction of a chromosome - binds chromatids together, contains the kinetochore, essential for chromosome separation -kinetochore: complex of DNA and proteins - spindle fibers attach to pull apart sister chromatids -chromatids: chromosome may consist of one chromatid or two sister chromatids *DNA in each pair of sister chromatids is identical* |
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homologous chromosomes |
-identical with respect to genes and centromere placement, contain identical loci- -expression of the same trait - each diploid organism had two copies of each gene (biparental inheritance) -alleles = alternative forms of genes -chromosomes in a pair can contain different or identical alleles -the alleles specifically control expression of the related trait |
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locus (pl. loci) |
-gene sites |
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human karyotype |
-pic of metaphase-shaped chromosomes (most highly condensed) -allele A and a = each have 1 form -categorized/paired up by size and centromere location -pic is simplified because only homologs, no sister chromatids |
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sex-determining chromosomes |
-females = two homologous Xs (XX) -males = XY -not true homologs because don't have same loci, but behave as homologs during meiosis (gamete formation) -gametic cells: mature reproductive cell such as egg/sperm in animals = halpod (23 chromosomes) -somatic cells: all cells in an organism which are not gametes |
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metaphase chromosome sizes/arms |
-metacentric: p = q -submetacentric: p < q -acrocentric: p << q -telocentric: p = 0 |
