Class Notes (839,189)
Canada (511,223)
BIOC15H3 (28)
Lecture 20

BIOC15Fall2013 Lecture 20 and Lecture 21.docx

8 Pages
146 Views

Department
Biological Sciences
Course Code
BIOC15H3
Professor
Karen Williams

This preview shows pages 1,2 and half of page 3. Sign up to view the full 8 pages of the document.
Description
BIOC15Fall2013 Lecture 20: Behaviour Genetics and Lecture 21 Drosophila locomotor activity o Ecolosion rhythm  emergence form pupa o Locomotor activity rhythm  movement o Measured locomotor activity to see if the absence of eclosion rhythm is due to the absence of the clock or just desynchronization between the flies o One sex comes out before the other and very shortly after light are on in the morning Drosophila: normal rhythm o Peaks occur around the same time each day, and about 12 hours apart o Mean locomotor activity o flies were tested individually in the locomotor-activity meter o Circardian rhythms o circardian rhythms are biological rhythms of about 24 hours – equal hours of day and night o clock genes are identified by mutations that change the period of rhythmicity hPer o human homolog of the Drosophila period gene o identification of genes influencing any human behavior is complicated by the other genetic influences, environmental influences and cultural factors o advanced sleep phase syndrome has been found to be due to an autosomal dominant mutation (circardian rhythm variant) o affected individuals are morning larks  go to sleep at 730 pm and wake up at 430am o they have a 4 hour sleep temperature and melatonin rhythm advance o attritubuted to hPer, homolog of the period gene in D. melanogasterflies and mammals per  The fruit fly circadian cycle shares three strong similarities with the mammalian: the per gene itself, CLOCK and BMAL regulation of per, and a gene called tau in hamsters and double-time (dbt) in flies, both of which encode the enzyme CKI o by reducing the phenotypic variance between each genotype and exaggerating the difference between genotypes we would have separated the population into three separate non overlappingphenotypic distributions, each characteristic of one genotype o to find a way to convert a quantitative trait into a qualitative (Mendelian) one we need to make the difference between th means of the genotypes large compared with the variation within the genotypes Example: Mouse behaviour 1 o two line of mice that breed true for two alternate behavioural phenotype o to do a norm of reaction study we must first create a group of identical individuals by repeated brother sister matings (inbreeding) o decreasing heterozygosity in inbreeding: o o it is possible to use genetically inbred model organisms to locate genes that contribute to the development of quantitative traits o genetic analysis detects genes only when there is some allelic variation QTL o genetic variation in quantitative traits is due to the segregation of alleles at several loci o even if it is impossible to individually identify all the genes segregating for a particular trait it is possible to identify the region of the genome where these quantitative trait loci (QTL) lie o o linkage disequilibrium two alleles separate together although not known to be linked o these deviations from what is expected by independent assortment of HW eq occur because of new physical linkage associations or population demographic events QTL mapping in mice o QTL for circardian rhythm of locomotor activity in mice o Inbred mouse strains B and D differing in the interval activity (t) were crossed to each other to develop 26 recombinant inbred (RI) strains o B and D RI strains also differed in large number of genetic markers (750) o o the RI lines were measured for their interval of activity (t) o a marker locus that is closely linked with a QTL will differ in its mean interval of activity fromone marker genotype to another o narrow heritability was estimated to be 55% o analysis identified a QTL at 45cM on chromosome 2 near a QTL known to be associated with wheel running o we can compare these results with the homolog, hPer2 o o the region different in patient with FASPS has the following amino acids around nucleotide 662 o 2 o there is a difference in patients with FASPS at 662 (G instead of S) o everyday data was collected about how often mice were active (their locomotor activity) o rodents are typically active at night (dark dots correspond to the night time) o mouse with serine at position 663 of mPer substituted for a Glycine have a shorter day (20.67 hours to 22 hours) compared to wildtype which is 23.7 horus Heritability of polygenic traits in humans can be studied using twins o Heritability o is a population not an individual measure o does not indicate how important genes are in influencing a character is population and environmental specific, it cannot be extrapolated from one population and set of environments to another Concordance of trait in two children raised in the same family o if the heritability is 0.0 (no variation in population) then there are no difference between MZ, DZ or unrelated by adoption (UR) o o if the heritability is 1.0, differences would be observed in MZ, DZ and UR o the extent of difference varies with the trait frequency o Heritability: Twin studies o the phenotypic correlations differing between MZ twins and DZ twins are often used in estimating heritability o MZ twins are treated more similarly than DZ twins  environment is almost identical for MZ o MZ may have greater social interaction than DZ o So environmental correlations are not the same as for identical twins as for fraternal, and heritability is overestimated 3 Is heritability fixed? o Studies have been made of he heritability of IQ p
More Less
Unlock Document

Only pages 1,2 and half of page 3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit