Clear and orderly summary of Chapter 10 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 10 – Chromosome organization and
molecular structure
Chromosomes; structures within living cells that contain genetic material
Genome; all the chromosomes and DNA sequences
Chromosomal sequences facilitate 4 processes;
1. Synthesis of RNA and cellular proteins
2. Replication of chromosomes
3. Segregation (scheiden) of chromosomes
4. Compaction of chromosomes
10.1 Organization of sites along bacterial chromosomes
BACTERIAL CHROMOSOMAL
DNA circular
Intergenic regions; regions
between genes, which are
untranscribed
Origin of replication; a part of the
chromosome that function as an
initiation site that begins DNA
replication. There is one origin
Repetitive sequences; short DNA
sequences that occur many times in a genome.
10.2 Structure of bacterial chromosomes
Nucleoid; region where chromosomes are found high
compacted. In mitochondria, chloroplast or bacteria. The
nucleoid is in direct contact with the cytoplasm.
bacteria 1 to 4 identical chromosomes per cell
Make bacterial chromosome more compact
- Formation of loops
Chromosome has a central core with loops
emanating(weggaan) from the core
Microdomains; 10 kbp
Macrodomains; 800 to 1000 kbp
To form micro- and macrodomains; Nucleoid-associated
proteins (NAPs) are needed; DNA binding proteins that facilitate
chromosome compaction
chromosome segregation (verbreking)
play a role in gene regulation
- Supercoiling
DNA coils already around each other.
Supercoiling; the additional coils in DNA due to twisting forces.
How effect the forces the DNA structure?
4 possibilities
, B and D are unstable and not occur in living cells
A, C and E differ only with regard to supercoiling. topoisomers
Chromosome function influence by supercoiling.
Chromosomal DNA in living bacteria is negatively.
The force of negative supercoiling promotes DNA strand
to sperate in small regions. This enhances genetic activities
replication and transcription that requires DNA strands to be separate
How become supercoiled? TENTAMEN
DNA gyrase (topoisomerase II); contains 4 subunites (2x A 2x B). It
uses energy from ATP. Circulair DNA + DNA gyrase + 2 ATP 2
negative supercoils. Zie process plaatjes hieronder!
DNA gyrase can untangle DNA molecules.
ATP is needed so the DNA held in the upper jaws can pass through the break and
move to the region of the lower jaws.
Topoisomerase I; bind to a negatively supercoiled region and introduce a break in
one of the strands. After the broken the DNA can rotates. Broken strand is then
repaired.
10.3 Organization of sites along eukaryotic chromosomes
EUKARYOTIC CHROMOSOME DNA linear. Humans have 2
sets of 23 chromosomes each.
Few hundred to thousand different genes, with millions of
base pairs.
Origins of replication; chromosomal sites necessary to initiate
DNA replication. There are many origins
Centromeres; play a role is segregation of chromosomes during
mitosis and meiosis. It provides an attachment site for kinetochore.
Kinetochore; group of proteins that attach to the centromere during
meiosis and mitosis, ensuring the proper segregation of the chromosomes
to each daughter cell.
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