Introduction Flashcards
DNA has hydrogen bonds between complementary strands, what other method increases DNA stability?
Base stacking
What interactions does base stacking involve
hydrophobic and electrostatic interactions
List the purines
Adenine and guanine
List the pyramidines
Cytosine, thymine and uracil
How many nucleotides make up the human genome?
3.2x10^9 nucleotides
How many autosomes and how many sex chromosomes exist
22 pairs of autosomes and 1 pair of sex chromosomes
How is DNA compacted
In a structure called a nucleosome
How many histone proteins make up the core nucleosome
Eight, homodimers of h2a h2b h3 and h4
Histone h1 binds with
linker DNA
Describe the structure of euchromatin
relatively open, active genes
Describe the structure of heterochromatin
highly condensed, late to replicate, inactive genes
Where is the telomere located
at the ends of the chromosome
Where is the centromere located
in the centre of the chromosome between the two arms
What is the short arm called and what is the long arm called
p and q
Describe a metacentric chromosome
the centromere is in the middle, the two arms are almost equal in length
Describe a submetacentric chromosome
the length of the arms are unequal
Describe an acrocentric chromosome
The p arm is so short that it is difficult to observe
Which chromosomes are acrocentric in the human genome
13, 14, 15, 21 and 22
Roughly what percentage do intergenic regions make up of the human genome
98%
What four types of DNA do the intergenic regions contain
repetitive DNA, pseudogenes, endogenous retroviruses and transposons
What is a gene
A DNA segment containing instructions for making a particular product, including the regulatory elements
Repetitive DNA sequences are patterns of nucleic acids that occur in multiple copies throughout the genome. How were they first detected?
Due to their rapid reassociation kinetics
What are endogenous retroviruses?
A subclass of a type of gene called a transposon
What are pseudogenes
functionless relatives of genes that have lost their ability to code protein
What are transposons/ transposable elements
they can change their position within a genome ‘jumping genes’
What is transcription?
the synthesis of a mRNA transcript from DNA
what is translation
the process by which cellular ribosomes create proteins
Where do the cells for cell preparation come from usually
lymphocytes, skin, amniocytes
How are cells arrested in metaphase
with the use of colchicine with prevents the formation of spindle
what does lysing with hypotonic saline do?
spreading of the chromosomes/ swelling - easier to view
What does the g in g banding stand for
giemsa banding
what is giemsa
a dna binding dye
what is a giemsa stain compared to
an ideogram
what is an ideogram
a diagrammatic representation of the karyotype that shows all of the pairs of homologous chromosomes in the nucelus
How is numbering of chromosomes done?
from the centromere outwards, chromosome number, the arm, the region and the band
what does cgh stand for
comparative genome hybridisation
what can conventional cgh detect
allele loss and gene amplification
why are microarrays now used instead of cgh
because cgh has low resolution, doesn’t give precise localisation of genes
what does cgh allow in terms of the genome
whole genome analysis
what is a microarray
an ordered assembly of nucleic acids immobilised on a solid support
what does each spot on a microarray contain
thousands of copies of the same nucleic acid sequence
what do different spots on a microarray contain
different genomic regions
what are the advantages of array cgh
detection of any type of gain or loss, faster, more sensitive
in an array cgh, the dna fragments from the test sample would most commonly be labelled with a ____ fluorophore
green
the green fluorophore from the test and the red fluorophore from the control sample would be
mixed and spread onto the microarray
what is detected by the computer to allow array CGH to work
the ratio of green to red
If there is a deletion in arrayCGH then the ratio of green to red will be
1:2
if there is a duplication in arrayCGH then the ratio of green to red will be
3:2
What does FISH stand for
fluorescent in situ hybridisation
what does FISH rely on
the fact that the DNA probe can anneal with its complementary target sequence on the metaphasic chromosome
What is DAPI
a fluorescent stain used in FISH
what is FISH used to detect
detect and localise the presence or absence of specific DNA sequences on chromosomes
What is DiGeorge syndrome
deletion of a small segment of chromo22 detected by FISH
FISH can allow whole chromosome paint probes to be used, this process is called
multiplex hybdrisiation
what is the advantage of multiplex hybdridisation
enables the visualisation of subtle translocations
