Lecture 33 Flashcards
What are the causes of variation?
• mutation - the original source of all variation
• recombination at prophase I of meiosis
• segregation of alleles at anaphase 1 of meiosis
• independent assortment of chromosomes at anaphase I of meiosis
• fertilisation between genetically different gametes
-variation to DNA structure but variation can be epigenetic as well
= not because the DNA structure is changed but because some external factor influences it
What is a microsatellite?
short tandem repeats (STR) - 2 - 9 bases – can have several alleles according to how many repeats (usually 7-40 repeats)
How do you detect variation in a microsatellite?
-
Where are STRs also used?
-in FBI investigations
What are the Single nucleotide polymorphism (SNP)?
-Single nucleotide polymorphism (SNP) 1 base – can only have two alleles at a locus
-only one base changed
about 10 millions SNPs in a human= accounts for lot of the differences in appearance. most of them however don’t leave any observable trace, by the difference in SNPs you can tell how closely you are related to someone
Is there association between SNPs and disease?
-yes
shows associtation between having a particular SNP and developing a disease so how likely you are to get it
What is the Hap Map?
The HapMap, will describe the common patterns of human DNA sequence variation
-To be a SNP has to occur in 1% population
About 10 million SNPs exist in human populations, where the rarer SNP allele has a frequency of at least 1%.
-apolipoprotein E and Alzheimers Disease ApoE gene!alleles E2, E3, and E4. Each allele differs by DNA base, and the protein product of each gene differs by one amino acid. one E4 allele; person will have a greater chance of developing Alzheimer’s disease
How can be SNPs detected?
- • DNA sequencing •
- restriction cutting site- the change results in the loss or gain of a restriction enzyme recognition sequence
What are the applications of all this?
• Paternity • Forensic analysis – Crime • Matching after a disaster
How do you use it for identifying the father?
-you can pick up microsatellite etc
only need the sample of the father and child= they should half match
What does it look like when you’re identifying the father? pic
-
How do you use it in forensic analysis?
-• Use several loci and estimate
probability
• Collect specific population data
How can you use if for matching after a catastrophe?
-Romanovs
What is population genetics concerned with?
Concerned with variation in whole populations: • measure the population variation • looks at factors affecting levels of variation
• explains why there are changes in the levels of variation in a population
applications:
-• Conservation genetics • Calculating disease risk • DNA forensics
What are the two main ways of calculating allele frequencies?
-when measuring variation= looking at allele frequency
got gene locus= have 1,2 or many alleles at that locus, polymorphism= more than 1 allele at that locus
1st way of calculation: relies on you being able to pick up the heterozygote genotype, (good with incomplete dominance and codominance)
2nd: harder and less accurate, make assumption,when heterozygote dominant and homozygous fominant= same phenotype (can’t distinguish them)
