Lectures 13 & 14: Quantitative Genetics Flashcards Preview

Introduction to Human Genetics > Lectures 13 & 14: Quantitative Genetics > Flashcards

Flashcards in Lectures 13 & 14: Quantitative Genetics Deck (37)
Loading flashcards...

What is Quantitative Genetics?

The study of the inheritance of characteristics that do not fall into distinct classes.


What are quantitative trait loci, QTLs?

Quantitative trait loci (QTLs) are stretches of DNA containing or linked to the genes that underlie a quantitative trait.


Define Heritability

The proportion of total variation in the population that is due to genetic variation


What does a high heritability indicate?

That there is a high proportion of the phenotype which can be attributed to shared genes, shared environments or both. High heritability does not indicate that the characters with high heritability are insulated from environmental effects


Define broad sense heritability

the proportion of total phenotypic variation which is due to genetic variation


Define narrow sense heritability

The proportion of total phenotypic variation that is due to additive genetic variation


Narrow sense heritability is easily measured in humans; T/F

False; applies more to animal and plant breeder because it determines responses to selection


T/F: Heritability is a ratio



What type of distribution is seen with quantitative traits?

Normal Distribution


What is "regression to the mean"?

When two people with similar quantitative characteristics mate and the offspring have the characteristic closer to the mean rather than the same measure of that characteristic


Why don't quantitative diseases follow the pattern expected of single-gene disorders?

There is an underlying liability in the distribution of complex diseases in a given population


What does liability mean?

The factors that contribute to the disease manifestation


What are the facts about multifactorial inheritance?

Most affected children have normal parents, Recurrence risk increases with the number of children affected in a family, Recurrence risk increases with severity of defect, rick of affected relatives falls off very quickly with the degree of relationship


Why does the affected relatives fall off quickly with the degree of relationship?

The many genes and environmental factors must combine to produce the disease-phenotype


What is correlation?

The tendency of two measures on different individuals, or two different measures on the same one, to vary in parallel.


Which two statistical measures are taken into account when calculating correlation?

Mean and Variance


What is covariance?

The multiplying of the deviation of a point on the x axis from the mean x and its deviation on the y axis from the mean y


What is the range for covariance?

-1 to 1


What does covariance measure?

Only the precision of the relationship between two variables but not the extent to which one increases given a unit increase in the other


What is the equation for heritability?

H^2 = Vg/Vp


What is the equation for Vp?

Vp = Vg + Ve + Vge


Does a strong genetic correlation disprove the importance of the environment in multifactorial traits?



Monozygotic twins are the result of..

One fertilization event followed by the separation of blastomeres into two groups during cleavage


Separation before trophoblast tissue formation at day 5 =

embryos have two separate chorions and amnions


Separation between day 5 and 9 is when

the amnion lining forms and thus the embryos have one shared chorion and two amnions


Separation after day 9 =

embryos share one chorion and one amnion


T/F Dichorionic MZs survive better than monochorionics

True, the later the embryo splits the more likely the twins are to be monochorionic or even conjoined


What is twin-twin transfusion?

When blood supplies are shared in the womb and one twin begins to take blood from the other. Donors grow to be anaemic and underweight whilst recipients are overweight and have heart problems.


What are adoption studies?

These are studies which compare adopted children with their biological parents and their adoptive parents. They share genes with their biological parents but not environments, but they share environments but not genes with their adoptive parents.


What was the conclusion of the adopted-away children studies of schizophrenia?

The incidence of schizophrenia in adopted-away children of schizophrenic mothers was ~10%, roughly the same as that of the children of schizophrenic mothers who bring up children in their own home.