Genetics summary – VU BMS 2020/2021
Simone Zweers
Reference: Brooker, Genetics: Analysis and prinicples, 7th edition
Chapter 8: variation in chromosome structure and number
1
, Genetics summary – VU BMS 2020/2021
Simone Zweers
Reference: Brooker, Genetics: Analysis and prinicples, 7th edition
- Genetic variation refers to genome differences between members of the same species or those of
different species
o Allelic variations = variation in specific genes
- Agricultural geneticists have discovered that such variation can lead to the development of new
crops
8.1: Microscopic examination of eukaryotic chromosomes
- Cytogeneticists are scientists who study chromosomes microscopically
o They compare chromosomes from many members of a given species
o Analysing chromosomes of more species to see the similarities/differences
o Analysing in actively dividing cells
- Most members of the same species have the same amount of chromosomes
- Three used features to classify and identify chromosomes
o Location of the centromere
o Size
o Banding patterns that are revealed when the chromosomes are treated with stains
- Chromosomes are classified with regard to centromere location as follows:
o Metacentric = centromere near the middle
o Submetacentric = centromere is slightly off center
o Acrocentic = centromere is significantly off center but not at the end
o Telocentric = centromere is at one end
- Short arm = p, long arm = q
- Karyotype = photographic representation in which all the chromosomes in a single cell have
been arranges in a standard fashion
- Some chromosomes have the same length and centromeric locations → detailed identification
necessairy → chromosomes treated with stains to produce charasteristic banding patterns (G
bands)
- Some regions of chromosomes bind the stain molecules heavily and produce dark bands
- Dark bands show regions that are more tightly compacted
- 300 G bands in human chromosomes in metaphase, 800 in prometephase
- Why is the banding pattern of eukaryotes useful?
o Individual chromosomes can be distinguished from each other
o Banding patterns detect changes in chromosome structure
o Banding assess evolutionary relationships betweens species
2
Simone Zweers
Reference: Brooker, Genetics: Analysis and prinicples, 7th edition
Chapter 8: variation in chromosome structure and number
1
, Genetics summary – VU BMS 2020/2021
Simone Zweers
Reference: Brooker, Genetics: Analysis and prinicples, 7th edition
- Genetic variation refers to genome differences between members of the same species or those of
different species
o Allelic variations = variation in specific genes
- Agricultural geneticists have discovered that such variation can lead to the development of new
crops
8.1: Microscopic examination of eukaryotic chromosomes
- Cytogeneticists are scientists who study chromosomes microscopically
o They compare chromosomes from many members of a given species
o Analysing chromosomes of more species to see the similarities/differences
o Analysing in actively dividing cells
- Most members of the same species have the same amount of chromosomes
- Three used features to classify and identify chromosomes
o Location of the centromere
o Size
o Banding patterns that are revealed when the chromosomes are treated with stains
- Chromosomes are classified with regard to centromere location as follows:
o Metacentric = centromere near the middle
o Submetacentric = centromere is slightly off center
o Acrocentic = centromere is significantly off center but not at the end
o Telocentric = centromere is at one end
- Short arm = p, long arm = q
- Karyotype = photographic representation in which all the chromosomes in a single cell have
been arranges in a standard fashion
- Some chromosomes have the same length and centromeric locations → detailed identification
necessairy → chromosomes treated with stains to produce charasteristic banding patterns (G
bands)
- Some regions of chromosomes bind the stain molecules heavily and produce dark bands
- Dark bands show regions that are more tightly compacted
- 300 G bands in human chromosomes in metaphase, 800 in prometephase
- Why is the banding pattern of eukaryotes useful?
o Individual chromosomes can be distinguished from each other
o Banding patterns detect changes in chromosome structure
o Banding assess evolutionary relationships betweens species
2
