Lecture notes from Imperial College London, Medical Biosciences BSc, 2nd year, genetics and genomics (GEN) module.
Focus on nuclear chromosomes: learn how 2 metres of DNA is somehow packaged into these tiny chromosomes and understand some key features of chromosomes that determine their structur...
Defining the Genome I - Chromosomes
Mitosis & Meiosis
- cytogenetic: field where microscopic analysis of cellular structures (specifically nuclear chr) is used
to investigate inheritance
- mitosis: normal cell division (somatic cells)
=> 1 cell divides into 2 daughter cells (division of sister chr)
=> follow a S-phase (chr duplication)
- meiosis: formation of gametes
=> 1 cell divides into 4 daughter cells with half amount of genetic inf. (haploid chr)
=> sex cells, gametes (sperm/ eggs)
=> 2 cell divisions: homologues (I) + sisters (II)
=> recombination between homologues (prophase I):
DNA from paired chr of parents cross over each other
to exchange nucleotide sequences => changed chr
, Cytogenetic and the human karyotype
- “metaphase spreads” to count chr: stop cell cycle in metaphase (condensed + distinguishable chr)
- X-shaped structure: pair of sister chromatides (DNA replication of 1 chr) joined at centromere
(end of each chromatid = telomere)
- karyotype = complete set of chr (numbered according to length)
=> determined via G-banding (dye Giesma stain chr: light/ dark bands), length, centromere position
22 homologous pairs (autosomes) + 2 sex chr (allosome)
(only father’s chr determine sex of child)
- euploid cells = normal chr number
- aneuploid = abnormal chr number
- fluorescent in situ hybridisation (FISH): DAPI stains chr
+ hybridisation of the fluorescently labelled DNA probes
identifies specific regions (telomere...)
Chromosomal theory of Mendelian inheritance
- Mid 19th: chr first seen
- Mid 19th: nuclear genetic material + inheritance through germ cells
- 1902: connection w/ Mendelian inheritance: homologous chr separate (haploid) and pair again
(diploid) during fertilisation
- 1905: gender determined by sex chr => genes carried by chromosomes
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller lisaribau. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $10.38. You're not tied to anything after your purchase.
