DNA Replication and Chromosomes: DNA and Chromosomes Flashcards
How is DNA packaging within chromosomes characterised?
Not constant.
How are more active DNA regions packed?
Less lightly.
How are less lightly DNA packed regions shown?
As bands on the chromosome.
How is Heterochromatin packed?
Tightly packed.
In how many forms does heterochromatin come?
In 2 forms.
Which are the 2 forms of heterochromatin?
- Constitutive.
2. Facultative.
What is the constitutive heterochromatin?
A permanent structure.
What does the constitutive heterochromatin contain?
No active genes: centromeres, Y chromosome.
What is the facultative heterochromatin?
A temporary structure.
What does the facultative heterochromatin contain?
Genes which are switched off sometimes: regions for embryo development switched off after completed development.
How is euchromatin packed?
Loosely packed.
What does eychromatin contain?
Actively-expressed DNA.
How can the chromosome structures be described?
Length of the arms relative to central bodyz.
Which is the central body in the chromosome structure?
The centromere.
What does the centromere link during replication?
A pair of sister chromatids.
Where do protein spindles connect?
To the centromere.
How are the protein spindles connected to the centromere?
Via the kinetochore.
Why do protein spindles connect to the centromere?
To move chromosomes within the nucleus.
What do telomeres define?
The end of the chromosome arms.
What do the telomeres help determine?
Age.
What happens to each chromosome during DNA replication?
It is duplicated.
Why is each chromosome duplicated during DNA replication?
To form the classic ‘X’ chromosome structure.
What does an individual have?
A copy of chromosomes from each parent.
How does a copy of chromosomes from each parent called?
‘Chromosome pairs’.
What do ‘chromosome pairs’ have?
Very similar sequences.
What can ‘chromosome pairs’ do?
Recombine.
What do ‘chromosome pairs’ give when they recombine?
Combinations of alleles.
How many re-arrangement between sister chromosomes are possible?
All sorts of re-arrangements are possible.
Which are the most often re-arrangements between sister chromosomes?
Moving/loosing large pieces of chromosomes.
What is karyotyping?
A modern diagnostic tool.
What can karyotyping identify?
Some genetic disorders.
How is karyotype produced?
5mL venous blood –> add phytohemagglutinin + culture medium –> culture at 37 degrees for 3 days –> add colchicine + hypotonic saline –> cells fixed –> spread cell onto slide by dropping –> digest with trypsin and stain with Giemsa –> analyse ‘metaphase spread’ –> karyotype.
What is a spectral karyotyping (SKY)?
A modern cytogenetic technique.
What can SKY do?
Identify all 24 humans chromosomes at one time.
How can SKY identify all human chromosomes at one time?
By using FISH probes.
What can an automated software examine?
Each chromosome for irregular patterns suggestive for genetic re-arrangements/known genetic conditions.
How can chromosomes be identified?
Based on size, shape and banding patterns.
What did mating experiments produce?
‘Recombination maps’.
What were the ‘recombination maps’ for?
Linking alleles with chromosomes.
With what were ‘recombination maps’ compared?
Physical maps.
What did physical maps incorporated?
DNA sequence.
What did recombination and physical maps allow?
Isolation of specific sequences.
Investigation of gene function.
Mutations’ effect.
For what are different types of map linking alleles and sequences valuable?
For population-level genetics.
Individual diagnostics.
Molecular biology investigations.
