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Lesson 3 nucleus dna-chromosomes

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Lesson 3 nucleus dna-chromosomes

  1. 1. To what extent can our genetics determine what we can be in life?
  2. 2. DNA: Chromatin, chromosomes
  3. 3.  Molecules that contain the all the genetic information of the individual.  Depending on how packed the DNA is we talk about: Chromatin: DNA molecules are more spread out in the nucleoplasm. DNA is normally in this state. Chromosomes: DNA molecules are highly coiled and packed forming specific structures. DNA only coils into chromosomes when the cell is going to divide.  The DNA molecules are made up of a sequence of bases which form codes.  These codes are the intructions for the formation of proteins. Proteins are responsable for carrying out all metabolic processes.  Each complete code that codifies for a protein is called a gene.
  4. 4.  When the DNA packs the resulting chromosome has 2 sister chromatids.  Sister chromatids: identical copies of a DNA molecule.  Each chromatid has 2 arms (p and q)
  5. 5.  All human somatic cells have 46 chromosomes (23 pairs) or 2 sets (2n)  Diploid cells (2n): cells with pairs of chromosomes.  The pair is made up by Homologous chromosomes.  Chromosomes that carry the same genes, but not necessarily the same genetic information.  They have the same shape and structure, and banding.  Human gamets have 23 chromosomes in total. Only one set of chromosomes (n).  Haploid cells(n): cells with only one chromosome of each type
  6. 6.  Each specie has a specific number of different chromosomes (n)  Their somatic cells have pairs of chromosomes 2n  Their gametes have only one set of chromosomes (n) Calculate the haploid number (n) for each species:(2n) Worksheet
  7. 7.  Carry same genes in the same locus, but with different (or not) information for each of the genes.  Somatic cells (diploid cells) carry 2 pieces of information for each gene. 2 chromosomes of each type.  One inherited from the mother and the other from the father.
  8. 8.  Chromosomes have the peculiar property of staining in bands, or chromosome segments, allowing the precise identification of individual chromosomes or parts of chromosomes. Definition from: MeSH via Unified Medical Language System at the National Library of Medicine  The chromosomes are visualized as consisting of a continuous series of bright and dark bands.  These bands are always the same in each chromosome, because the position of the genes and therefore bases in the DNA is always the same.  The specific position of a gene is called the gene locus.
  9. 9.  Organized positioning of chromosomes extracted from a cell.  by size, structure and centromere position, and bands  Gives information on the number of chromosomes of an organism.
  10. 10. Human karyotype: (somatic cell)  Shows 23 pairs of chromosomes in total  22 pairs of autosomes and 1 pair of sex chromosomes.  Sex chromosome pair can be:  XX : in females  XY: in males
  11. 11. 1. Is it genetic material of a diploid or haploid cell? 2. Is it genetic material of a uman or non human cell? 3. Is it genetic material of a male or female individual?
  12. 12. 1. Is it genetic material of a diploid or haploid cell? 2. Is it genetic material of a human or non human cell? 3. Is it genetic material of a male or female individual?

Hinweis der Redaktion

  • Supercoiled DNA around Histone proteins.
  • A band is clearly distinguishable from its adjacent segments by appearing darker or brighter

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