Biology HL
Biology HL
4
Chapters
553
Notes
Theme A - Unity & diversity
Theme A - Unity & diversity
Theme B - Form & Function
Theme B - Form & Function
Theme C - Interaction &  Interdependence
Theme C - Interaction & Interdependence
Theme D - Continuity & Change
Theme D - Continuity & Change
IB Resources
Theme A - Unity & diversity
Biology HL
Biology HL

Theme A - Unity & diversity

Unlocking The Mystery Of Chromosome Evolution

Word Count Emoji
608 words
Reading Time Emoji
4 mins read
Updated at Emoji
Last edited on 15th Oct 2024

Table of content

Karyotyping& karyograms

  • Karyotyping is a process where chromosomes become visible when cells are dividing, with the most clarity during the metaphase. Think of this as the cell's family photo shoot - where each member of the family (chromosomes) comes together and poses for a picture!
  • To get the chromosome picture, cells are stained and placed on a microscope slide, and then gently burst to spread the chromosomes. It's like a chromosome firework show!
  • Using a microscope, scientists can find cells where the chromosomes don't overlap, and take their photographs. It's just like sorting through a pile of family photos to find the perfect shot.
  • With digital technology, we can now arrange chromosomes in an orderly manner based on differences in banding patterns, size, and centromere position.
    • Banding patterns are like the distinctive fashion styles of each chromosome.
    • Size differences are evident, just like in a family, where the eldest (chromosome 1 in humans) is the largest, and the youngest (chromosome 21 in humans) is the smallest.
    • The centromere, holding the two chromatids of each chromosome together, varies in position, just like how in some families, the mom or dad might be the more dominant parent!
  • The sorted image of the chromosome is called a karyogram. So, if karyotyping is the family photoshoot, the karyogram is the final family portrait!

Primate chromosome numbers

  • Human cells contain 46 chromosomes, while our primate cousins - chimps, gorillas, and orangutans - carry 48. Imagine going to a family reunion and finding out you have fewer cousins than you thought!
  • One hypothesis suggests that our chromosome 2 is the result of two primate ancestor chromosomes merging. Imagine if two of your cousins decided to become a team and henceforth be known as a single entity!
  • This hypothesis can be tested by comparing human chromosome 2 with chimpanzee chromosomes. If they show similar banding patterns, it would suggest a shared ancestry.
  • Moreover, if this fusion happened, we would expect to find remnants of the 'glue' (telomeres) that held the original chromosomes together at the fusion point.
  • Also, there would be remnants of a second centromere because each original chromosome would have had one. It's as if, when two cousins team up, one can't simply forget their old house; there would be some signs left behind.

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IB Resources
Theme A - Unity & diversity
Biology HL
Biology HL

Theme A - Unity & diversity

Unlocking The Mystery Of Chromosome Evolution

Word Count Emoji
608 words
Reading Time Emoji
4 mins read
Updated at Emoji
Last edited on 15th Oct 2024

Table of content

Karyotyping& karyograms

  • Karyotyping is a process where chromosomes become visible when cells are dividing, with the most clarity during the metaphase. Think of this as the cell's family photo shoot - where each member of the family (chromosomes) comes together and poses for a picture!
  • To get the chromosome picture, cells are stained and placed on a microscope slide, and then gently burst to spread the chromosomes. It's like a chromosome firework show!
  • Using a microscope, scientists can find cells where the chromosomes don't overlap, and take their photographs. It's just like sorting through a pile of family photos to find the perfect shot.
  • With digital technology, we can now arrange chromosomes in an orderly manner based on differences in banding patterns, size, and centromere position.
    • Banding patterns are like the distinctive fashion styles of each chromosome.
    • Size differences are evident, just like in a family, where the eldest (chromosome 1 in humans) is the largest, and the youngest (chromosome 21 in humans) is the smallest.
    • The centromere, holding the two chromatids of each chromosome together, varies in position, just like how in some families, the mom or dad might be the more dominant parent!
  • The sorted image of the chromosome is called a karyogram. So, if karyotyping is the family photoshoot, the karyogram is the final family portrait!

Primate chromosome numbers

  • Human cells contain 46 chromosomes, while our primate cousins - chimps, gorillas, and orangutans - carry 48. Imagine going to a family reunion and finding out you have fewer cousins than you thought!
  • One hypothesis suggests that our chromosome 2 is the result of two primate ancestor chromosomes merging. Imagine if two of your cousins decided to become a team and henceforth be known as a single entity!
  • This hypothesis can be tested by comparing human chromosome 2 with chimpanzee chromosomes. If they show similar banding patterns, it would suggest a shared ancestry.
  • Moreover, if this fusion happened, we would expect to find remnants of the 'glue' (telomeres) that held the original chromosomes together at the fusion point.
  • Also, there would be remnants of a second centromere because each original chromosome would have had one. It's as if, when two cousins team up, one can't simply forget their old house; there would be some signs left behind.

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Dive deeper and gain exclusive access to premium files of Biology HL. Subscribe now and get closer to that 45 🌟