Lecture 8 Flashcards
Why is it challenging to map human chromosomes?
Inability to perform crosses, typically families only have a small number of progeny so only pedigrees can be used, however as each chart only provides a small amount of data several charts from several different families must be used in order to test for independent assortment
Why was the X chromosome the first human chromosome to be mapped?
It was easier to perform recombination analysis on it as males are hemizygous for X-linked genes so by looking at only male progeny from a dihybrid female you can effectively sample her gametic output (like a testcross)
What is somatic cell hybridisation?
The fusion of two different types of cells, these cells can then be altered by viruses or if they are derived from tumours they will go on to live indefinitely and the nuclei will fuse?
What is heterokaryon and how does apply to research of the human genome?
Heterokaryon is when cells from different species fuse and therefore have two nuclei from different species these nuclei then fuse with the chromosomes from one species being preferentially lost.
In mouse-human cells the human chromosomes are preferentially lost resulting in different cell lines which have retained different chromosomes, the different cell lines can then be characterized resulting in the identification of gene products which are only present in cell lines which have a particular chromosome allowing us to map this gene to this chromosome
How can the precision of somatic cell hybridisation be improved allowing genes to be localized only to certain parts of chromosomes?
By irradiating the cells the chromosomes will be damages and will lose segments, we can then observe which cell lines have the product and which section of the chromosome they have all retained in common to localise the gene to that chromosome segment
What is In situ hybridisation?
A method where the location of a gene on a chromosome, where the chromosome is denatured and a probe which is fluorescently labelled and complimentary to the gene being search for is used to identify the location of the gene
What is the value of in-situ hybridisation with regards to genetic mapping?
Now there are many more genetic markers available
What are the different types of DNA markers?
Minisatellites which are based off tandem repeats 15-100bp long
Microsatellites which are based of tandem repeats only 2-6bp long
What is a restriction fragment length polymorphism?
A SNP that alters a restriction enzym recognition site
What is a SNP?
Single nucleotide polymorphism which is a position where people differ in a single nucleotide base
What are genome wide association studies?
A process of looking for no random associations between a rait and alleles scattered across the genome
Mutation appears on a particular chromosome it can then be given a haplotype to potentially give linkage disequilibrium
