Clear and orderly summary of Chapter 8 of the book "Genetics: Analysis and Principles, 6th Edition by Robert Brooker". Together with all my other summaries of Genetics I got an 8,5 for this course.
Genetic summary Chapter 8 – Variation in chromosome structure and
number
Genetic variation; genetic difference among members of the same species or among
different species BIG
Allelic variation; genetic variation, that occurs two or more different alleles SMALL
8.1 Microscopic examination of eukaryotic chromosomes
Cytogenetics; scientist who study chromosomes under the microscope
Chromosomes are visible during cell division.
Classify and identify chromosomes
1. Location of the centromere
- Metacentric
- Submetacentric
- Acrocentric
- Telocentric
P; short arm Q; long arm
2. Size
Karyotype; photographic representation of all the
chromosomes in a cell. Largest chromosomes have the
smallest number. Sex chromones are an exception!
3. Banding patterns, revealed when chromosomes are
treated with stains (kleur)
G bands; banding pattern that is observed when
chromosomes are treated with chemical dye Giesma.
Chromosomes bind to the dye and produce dark bands/ the stain binds and
produce light bands
Left chromatid of each pair; banding pattern during metaphase
Right chromatid of each pair; banding pattern during prometaphase → more
bands → chromatid is less compact
Karyotype comes in EXAM! Bijv. 3x 21 → down syndrome
Useful;
- Distinguish (onderscheiden) chromosomes that are similar in size and
centromeric location
- Identify changes in chromosome structure
- Explore evolutionary relationship between species
, 8.2 changes in chromosome structure;
an overview
Mutations
1. Deletion/deficiency – change in the
total amount of genetic material
Section of chromosomal material is
missing
2. Duplication – change in the total
amount of genetic material
Section of chromosomal material is
repeated
3. Inversion – rearrangement
(herschikking)
Section of chromosomal material is
flipped so it runs the opposite
direction.
4. translocation – rearrangement
(herschikking)
Section of chromosomal material become attached to a different chromosome
or to a different part of the same chromosome
- simple translocation; single piece of chromosome is attached to another
chromosome
- reciprocal translocation/balanced translocation; two different chromosomes
exchange piece
8.3 Deletions and duplications
Deletion
- terminal deletion; deletion at the end
- Interstitial deletion; deletion within the
chromosome
Phenotypic consequence; depends on the size of the
deletion and of it includes genes that are vital to the
development of the organism. Disease cri-du-chat
syndrome. MORE HARMFUL THAN DUPLICATION.
Nonallelic homologous recombination; recombination that occurs at
homologous sites (repetitive sequence) within chromosomes, where the sites
are not alleles of the same gene. → result one duplication and one deletion.
Duplication
Segmental duplication; duplication in which a small segment of a
chromosome ends up with more than one copy of the same gene.
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