Lect 5 Flashcards
Chromosome painting
It is a technique that allows the visualization of chromosomes and the regions why hybridization with fluorescent DNA probes producing different colors at each side of hybridization
Why chromosome painting
To detect numerical and chromosomal aberrations relationship with diseases
Used on
Animal and human chromosomes for cancer
Recently on plants
FISH provides intense and…fluorescent staining at …and…
Specific
Metaphase
Interphase
First identified translocated chromosome in human neoplasia
Philadelphia chromosome
T(9:22)(q34:p11)
Each homologous pair of chromosomes are
FISH depends on..
Similarly painted
Computer analysis softwares
B chromosomes are…..
Due to….
Extra chromosomes to the standard complement and non essential
Inter and intraspecies crosses
B chromosomes are……jumping genes
They display . Inheritance
They collect….and…
Transposons
Non mendelian
Transposons and repetitive DNA
B chromosomes help scientists study…and in…
Centromeres
Genetic engineering
B chromosomes are also called
…eukaryotes
…mammals
Supernumerary chromosomes
15%
1.2%
The 3 main characteristics of B chromsomes
Non essential
Morphology distinct from As
Display non mendelian inheritance
Are B chromosomes in all members of a species?
They vary in…and…
Example with grass
No
Copy number, in an individual, acc to tissue
No in roots but in aerial tissues and gametes
B chromosomes are usually….
Size in plants
Size in mammals
Heterochromatinised
Smaller then smallest As
Similar to As
Do As and Bs pair and combine during meiosis
No
What is a meiotic drive
The bias in the transmission of certain alleles or chromosomes during meiosis
Why Bs show non mendelian drive
To allow accumulation and inheritance at greater ratios
Plants drive
Post meiotic nondisjunction in gametophytes, no proper separation of gametes after meiosis resulting in abnormal no of chromosomes.
Premeiosis, during meiosis
After fertilisation like oocytes of parasitic wasp
Bs with drive in mammals usually have
Meiotic drive in females
Bs freq is independent of…..
But larger….has…
Genome ploidy
Genomes more Bs
…..Bs are…..with pollution and stress
More Bs=….=….
Vertebrates
Positively correlated
Larger cell size, more mass, longer mitosis, low RNA levels
Bs applications
Amenability for research
Maize Bs
BA translocations and non disjunction
Mapping loci on maize As
Engineering minichromosomes
Bs in maize
loci mapping, centromere biology, gene dosage, engineered minichromosomes
Reciprocal translocations between As and Bs can lead to…..during…leading to
disjunction
Meiosis
Sperm with varying no. Of chromosomes
BA translocations are in all maize As expect ….
Allows the ….of chromosome arm where….
8s
Identification
Gene of interest is present
Do cells with damaged Bs suffer from aneuploidy
No
Artificial chromosomes are
Synthetic chromosomes with DNA fragments integrated into a host chromosome.
Non viral, non bacterial DNA into bacterial chromosome then expressed and continues with host
Artificial chromosomes are used for
Transfection of cells
Why use BAC not YAC
More stable
No chimeric effect
Plasmid vs BAC vs YAC
10k
300k
1 million
What is the chimeric effect
For the gene to be expressed in some cells but not the others in the same organism
Advantages of BAC
Larger genes
Several genes at once
entire viral genome
The process of introducing BAC
Results
Media
Foreign DNA is ligated into lac z gene of bacterial F plasmid
BAC is electroporated into E.coli
Positive is white
Negative is blue
Media is x gal
Prokaryotic chromosome structure
Folded genome
50-100 loops each -vely supercoiled
DNases vs RNases
DNase cleaves a site to relax supercoiling at the site
RNase destructs DNA connectors causing unfolding but no effect on supercoiling
Eukaryotic chromosomes arrangement
Digestion of DNA with an endonuclease
Multineme, multiple molecules per chromosomes
Unineme, proved 1 DNA molecule per chromosome
200bp in length for nucleosomes
Which plants were B chromosomes identified in
Do all Bs exibit drive mechnisms
Rye
Maize
No
Sometimes drive in one sex is balanced by…through the other in B chromosomes
Drag
Researchers can cross recessive mutants ofB-A chromosmes if expressed…
Gene locus identified
E.coli bp
Human bp
Each chromosome in human bp
Largest human chromosome nm
4.710^6
310^9
50-25010^6
8.510^7
