Hardy-Weinberg Equilibrium: Factors Influencing Genetic Variation

This assignment provides a detailed explanation of the Hardy-Weinberg equilibrium principle, which states that genetic variation in a population remains constant from one generation to the next in the absence of disturbing factors. It identifies factors like non-random mating, natural selection, genetic drift, mutation, and gene flow that can disrupt this equilibrium. The assignment includes calculations related to allele frequencies based on given data, an analysis of genotype frequencies, and a discussion of lethal alleles, including examples like cystic fibrosis and sickle cell anemia. It also provides calculations for determining the frequency of carriers for diseases like Tay-Sachs within a population, demonstrating the practical application of the Hardy-Weinberg principle in understanding genetic traits and disease prevalence.

Population genetics
Introduction
The Hardy Weinberg equilibrium refers to a principle of genetic. The principle states that the genetic
variation in any population will always remain constant from one particular generation to the
subsequent generation provided disturbing factors are absent. This law predicts that both the genotype
and the frequencies of allele will remain constant since they are in equilibrium in the presence of
random mating. The principle can however be disrupted or disturbed by a number of factors. Some of
these factors include the following; on random mating, natural selection, genetic drift, mutation and
gene flow. During the process of mutation, the equilibrium of allele frequencies is disrupted by
introduction of another new alleles into the population. Also natural frequencies and processes of
nonrandom mating will always lead to the disruption of the principles considering that they change the
allele frequencies. This will happen since some of the alleles assist in the destruction of the reproductive
success of the living organisms that possess them. Another important factor that can potentially disrupt
this particular principle is genetic drift. This will always happen when allele grows higher or lower
through probabilities. This particular phenomenon is common within small populations. Due to the
factors that have just been mentioned, this particular principle rarely applies in reality. The principle
therefore describes an idealized state and also variation in the genetics that can actually be measured as
it changes from the state of equilibrium.
PART A paper tasting test
CONTROL
12
7
10
15
44
THIOUREA
Y
1
9
10
27Y 17N
SODIUM BENZOATE
Y6
5
7
9
27Y 17N
PTC
Y4
0
8
6
Y 26N
This implies that 27 are tt and q2=27/44
Also 26 are tt and the subseqwuent calculation becomes;
Thus q2=26/44,the squareroot of the answer gives 0.7687.This makes the frequency required to be 77%
=t is equivalent to 77%.In the data above,18 samples were either Tt or TT.This implies that p2=1-q
P2=0.23 and therefore p=0.05.The frequency of the TT genotype becomes 5%.Also fTt =0.35
Using the formular for equilibrium,
It follows that q2+p2+2pq =1
Thus 0.6+0.05+0.35=1

PARTB
HW equilibrium without selection
Genotype frequencies; This particular part will describe how often we see each ale combination.
Frequency of TT=6/9=0.67
Frequency of Tt=1/9=0.11
Frequency of tt=0.22
Allele frequencies overtime. This will describe how often each allele will be seen.
Frequency of TT=13/18=0.77
Frequency of t=5/18=0.28
PART C
Alleles that make or cause death of the organism is called lethal alleles. The gene that is usually involved
is called an essential gene. The discoveries have revealed that a mutant allele can potentially cause
death. The mutation of such essential genes normally results into a lethal phenotype. If the mutation
that is happening is as a result if dominant lethal gene or allele, which can either be homozygote or
heterozygote, then the resulting allele must be lethal. In the cases of the mutation being caused by the
recessive lethal allele, then the homozygote for this particular allele will potentially have phenotype that
is lethal. It is important to note that most of the genes that are lethal are recessive ones. Some of the
diseases that are caused by such genes are cystic fibrosis, sickle cell anemia among others. In the
heterozygous form, recessive lethal alleles do not cause death. This due to the fact that a certain

threshold of the required protein is kept. It is only when this threshold of the protein is not met that
death do occur.
Calculations
Assuming the population under target is at 20 000 and out of this population 2 individuals have the
disease of Tay-Sachs,the frequency of “aa” will be given as 2/20000 ;
Using the equation
P2+2pq+q2=1,then q2=0.0001
The calculation of p becomes p+q=1 which implies p=0.99
The carriers of this particular diseases will be heterozygous individuals=2pq
=2*0.99*0.00001
=0.02 the frequency thus translate to 2%.
In smaller set up of class the number may be regarded as 2x50+20/200=0.6 in which 2N=200 thus
frequency will be calculated for allele as shown 0.5+1/2(0.2)=0.6.
Frequency of phenotype =0.3TT+1/2(0.2Tt)=0.4
PART E