now that we have understood couple of psychological
processes such as how do we perceive how do we understand the world how do we retain information
that we acquire in our life how emotion gets triggered now let us come to a very different
type of a topic which has it’s origin in a controversy why are we the way we are is it
that behave in heritage certain things from our parents and therefore we behave in a particular
way or is it that we have acquired certain things from our environment which makes us
react to situation the way we do so nature nurture controversy that you always
read about that you always hear about that is what we are going to discuss today my basic
intension is basically to introduce you two certain facts scientific facts that has to
do with genetics and then i will now take up certain findings of behavioral genetics
to tell you that how is it that now people give credit for that type of situation to
the genetic makeup as well as to the environmental factors the external factors
so we would be basically talking about the gene environment interaction and how this
interaction of the genetics and the environmental determinants they provide base to our behavior
now look at your screen you see two kids and then the obvious thing that you basically
look at is the resemblance between the faces of these two children now this is something
that we have always been told ah that see if you have a twins later on we will even
discuss fraternal and identical a twins so if you have no children of the same parents
if you have members of the same family and so for people do search for certain resemblance
that resemblance could be in terms of their appearance and that resemblance could be even
know for certain other thing so right now they took it that you look at you search for
similarity in their physical appearance did you find anything look at this now both of
them have grown up a bit again look at the resemblance between their faces now again
try to match now when they are younger compared to when they became little older and now when
they have further grown up so the same kid three different life stages of these two siblings
and you look at their resemblance now resemblance is something that we always ah now look for
when we look at any two objects here it is the human faces psychologically what we would
be interested in is the resemblance in the pattern of response so the sibling that we
saw here do they know reflect certain type of you know mirror image in terms of their
behavioral response say for instance their pattern of interacting with others their pattern
of say certain choices their know behavioral manifestation of certain emotional states
is they are a resemblance and this is something that you know ah psychology gets interested
in and this what brings genetic and psychology come together
from the behavioral science point of view when we look at the human being we tried to
understand his or her personality intelligence memory problem solving ability thinking style
and so far we are more interested in understanding the ability of what ah this very individual
can do what we would do as part of you know this very discussion is we would initially
know spend some time understanding the genetic inheritance pattern then we would come across
certain key terminologist we will try to understand them what each of them mean then we would
also understand you know ah two basic processes biological processes the process of mutation
and recombination that provides variation to human beings both in terms of their appearance
as well as in terms of their behavioral manifestations and once we do all this then we would gradually
move towards you know behavioral genetics where we would be taking a specific type of
behavior a specific type of psychological abilities and then try to see how much of
credit for this type of inability can be given to either ah psychology the environment or
the genetics we will even not take care of certain issues
like say autism dyslexia ok so we will know try to take no variations of examples right
from normal to clinical staff and then try to know understand how this gene environment
interaction takes place so coming back to the basis of genetic inheritance we all know
that human beings have twenty three pairs of chromosomes and of this twenty three twenty
two are autosomes know on your screen you see these twenty three ah pairs one pair is
sex chromosome as i told you that we all have d three pair of a chromosomes twenty two pairs
are autosomes and one is the sex chromosome so if you inherit x x from the two parents
the father and the mother then you become ah female and if you inherit y from the father
and x from the mother then you become a male so this is now the basic genetic inheritance
that we are aware of chromosomes usually this is how you see and then know on the right
hand side you see the d n a structure the double helical structure ah and the genes
now it has been understood that there are certain traits that pass from parents to children
ok now behavioral genetics is that branch of
science which basically looks at the passage of traits from the parents to children now
remember we are not talking about the passage of genes from know parents to children rather
we are talking about the trait if you remember know the trait approach to personality talks
about certain ah basic so certain basic characteristics ah cardinals trait secondary traits ok so
actually what happens behavioral genetics understands excepts and explains that the
traits they pass from ah parents to children and this is how it [transget/transmitted]
transmitted from one generation to the other the second important thing that environment
also exerts certain selective demand so the environment in which you are it compels you
to adapt to the situation and therefore certain ah demands are exerted on you now human beings
they live at the intersection of these two so you have the passage of the traits you
have the passage of the genes and at the same time there are certain extra news demands
environment impose on you and therefore what happens the nature and the nurture they act
together to shape us an individual the way we look took in our real life to others
now d n a is basically comprised of four different nucleotides which are also called as bases
know at adenine thymine guanine cytosine so these are the four bases so these are the
four nucleotides now what happens that these nucleotides they form pairs so a t and c g
these are the two pairs so adenine and thymine they pair together and cytosine and guanine
they pair together now the genes that we are talking about they are basically segments
of d n a that carrying instructions for making any specific protein ok and some time it could
be even true for certain r n a is also now on your screen what we seen is the structure
of adenine thymine cytosine and guanine how they a look like chemically ok and when they
form the pair now cytosine and guanine you see on the top and adenine and thymine you
see at the bottom so this is the pair that we have
so the double helical structure of gene that we have ok we have a sequence of a t c g bonds
that is overlaid over it now a gene might have a few hundred to over
a million base pairs ok and as we discussed right now that we all have twenty three pairs
of chromosomes and a chromosomes has ah know a some few hundred to few thousands genes
and these twenty three pairs of chromosomes they constitute the human genome and hence
we all have somewhere around thirty three thousand to forty thousand genes in us and
approximately six billion d n a base pairs now we come to mutation mutation basically
is a process of change in the genomic sequence and such changes basically a know it could
range from a single d n a base to a segment of a chromosome mutations are of two types
the germ line mutation and the somatic mutation germ line mutation basically is hereditary
mutation so it is inherited from the parents such type of changes ok which gets transmitted
to the child from their biological parents that is germ line mutation but if you acquire
the change so now if mutation is there in the d n a of certain cells due to environmental
factors say for instance ultraviolet radiation little later we will come to one such example
also so if you have know a change a mutation ok which is a consequence of an environmental
factor then it is called as somatic mutation now although all of us say ah obvious body
parts ok none of us exactly look a like so my face is different from yours and yours
is different from the third person and even this variation know between the human beings
that you see it could be either because of mutation germ line or somatic mutation ok
or it could be because of recombination so even identical twins they might have no different
in the shape of the face even though they share same d n a and they also differ in terms
of even metabolism of his specific substances we will take the example of little later now
let’s talk about recombination so right now we talked about mutation the both the germ
line and somatic mutation one that is inherited in nature and other one which is acquired
which is a consequence of environment so what basically we see here in terms of mutation
is that there is a role played by the genetic factor and there is also a effective role
that is played by the environmental factor and therefore both these factors they played
their own significant role as far as mutation is concerned
now we are coming to recombination in normal circumstances one inherits so one chromosome
from the father and one from the mother and this process is repeated in the next generation
as well ok however this chromosome is not the intact one you inherited from the mother
and the father rather it is a combination of the two and this recombination is basically
the genetic mechanism of producing more and more genetic variation ok and such variation
would not have been possible had the whole chromosome been transmitted
so the whole chromosome is not transmitted and therefore it facilitates the process of
a genetic variation and these variations are considered to be desirable the reason being
that if variation doesn’t take place ok then what would happen that the likelihood of the
survival of any species ok would be minimal if there is a change in the environmental
circumstance now think of various types of environmental changes that takes place you
realized at species which have more and more genetic variations they survive so if say
we are say some where if ten of us are there and if there is and we all are genetically
different and if there is a variation in the environment which makes one of us to that
variation at least nine would survive and if several several several such sequences
come then also human race will finally succeed surviving simply because all ten of us were
genetically very different so you can think the number of no variation
the type of variations the extent of variation in the human race and why this is a desirable
trait simply because it allows the human race to survive irrespective of all types of changes
that takes place in the environment now we come to certain important terminologies polygenic
phynotypic genotypic dominant and recessive these are the five terminologies that will
first define and then we will talk again about the behavioral genetics
let us come to polygenic now this is the term which is used for traits whose phenotype is
influenced by more than one gene ok so each of the gene has some additive effect now what
is phenotype we will come little later but basically the physical appearance for example
if you take now if the physical appearance is determined by more than one gene where
each gene makes some additive effect so if there are seven separate genes which now determines
the phenotype that you are looking at and all of them have some incremental effect so
some total of this seven genes their effect becomes a particular phenotype and each of
them defines one aspect of it so that is you know ah polygenic because it is more than
one then we come to phenotypic this is of course
the observable trait so physical appearance for instance anything that you can observed
in the living organism that is the phenotype then we come to the genotype which is the
reverse of phenotype genotype represents the genetic makeup of the living organism and
because it is genetic makeup here therefore you cannot actually observe it so basically
it is you know the biologist who map your genetic makeup and that genetic makeup tells
you why you are ah know having a particular type of a trait visible trait and why your
children have a different trait which you do not have
say for instance you are a black eyed person the color of the eye ball is black and you
realize that ah one of your child has a brown eye ball ok now that is a variation overly
you think that phenol typically you are black eyed person where as there could be possibility
that the genetic makeup that you have basically has a recessive character ok so the dominant
one right now we will talk about the dominant and the recessive ah genes also but the dominant
one gets represented and therefore what you see outwardly the phenotypic trait that is
of the black eye ball that we are talking about is not something which actually gets
equally represented in your genetic makeup so in your genetic makeup you have a dominant
blackness of the eye ball where as you are recessive brownness of the eye and therefore
the child the biological of spring you know has ah phenotypic trait which actually represents
the recessive character that you are carrying in your gene so there is no always something
more to phenotypic trait that is observed to the outer world ok which is apparent in
the genetic makeup so genetic makeup has a larger and broader
image of what you actually carry besides what you actually look like then we come to the
dominant genes genes whose inheritance makes the out word display of the trait ok so basically
those genes which now expresses itself for right now the example that we took now ah
the say black eye a color of their skin color of the hair texture of the hair all of these
are know dominant genes where as the genes which do not allow ah itself to get to expressed
completely basically the dominant gene doesnt allow them to express those genes are called
recessive genes ok so the brownness of the eye ball that we were referring to was the
recessive trait that you are carrying your genetic makeup had that where as the black
dominant eye ball was that trait got that got reflected in you and that dominant gene
did not allow the recessive one the brownness to get reflected in you recessive gene we
have talked about as the name suggest they are basically masked by the dominant gene
so they are expressed only in the homozygous state let us understand genetic inheritance
of traits by this example here you have the father and the mother who are carriers of
a given disease the blue color represents unaffected individuals where as the black
color represents individuals affected by the disease combination of both the colors represent
that the individuals are carrier of the disease here when both the parents are carriers the
first off spring is completely unaffected by the disease the second and the third off
spring are carriers where as the forth off spring is affected by the disease
now the big question is to understand the relative contribution of genetic inheritance
and environmental determinants of any human behavior we have seen that we have the dominant
genes we have the recessive genes we have seen know how a combination of genes they
affect the behavior in the polygenic state there are dominant gene that doesnt allow
the expression of a particular trait but then you also have selective demands that are put
forward by the environmental conditions and for the healthy survival one has to actually
show competence that irrespective of the adversity of the environmental condition one can survive
so having defined ah know these four five definitions and having understood that there
is a beauty and there is a biological mechanism of mutation and recombination which makes
us look different now when we meet next we will be talking about behavioral genetics