The Hardy-Weinberg Equilibrium states that allele and genotype frequencies in a population will remain constant in the absence of evolutionary influences. It provides a mathematical framework for studying genetic stability and is based on principles of random mating, large population sizes, and the absence of natural selection, migration, and mutations. The document discusses the application of the Hardy-Weinberg equation and real-world examples, emphasizing its significance in understanding population genetics.

1. Hardy
Weinberg
equilibrium
Submitted to: Dr. Khalid
Mukhtar
Submitted by: Amna Akram
Roll no.: ZOOL51F22R002
BS ZOOLOGY

2. Hardy Weinberg
equilibrium
Submitted to: Dr. Khalid Mukhtar
Submitted by: Amna Akram
Roll no.: ZOOL51F22R002
BS Zoology 5th regular
University of Sargodha

3. Introduction
• In population genetics, the Hardy–Weinberg principle,
also known as the Hardy–Weinberg
equilibrium, model, theorem, or law, states
that allele and genotype frequencies in a population
will remain constant from generation to generation in
the absence of other evolutionary influences.

4. History
• Independent Discovery (1908):
• ○ Godfrey Harold Hardy: A British mathematician who
formulated the principle in a letter to the Science magazine.
○ Wilhelm Weinberg: A German
physician who independently derived the same principle.
• Significance:
○Provided a mathematical framework to understand genetic
stability in populations.
○ Challenged the prevailing notion that dominant alleles would
automatically increase in frequency.

6. Basic concepts:
• Genome-
Complete set of DNA, including all of it’s genes(of
organism). In human being, copy of entire genome more than
3billion DNA base pairs in all cells that have nucleus.
• Gene frequency-
Relative proportion of a particular genes or alleles of single
locus in a population. When we consider a particular gene on
single locus in population, then we note the probability of a
particular genes. One character dominant in a population while
other is recessive.

7. Cont…
• Genotypic Frequency-Relative proportion of
a particular genotype in population.
• Population Genetics-Study of allele
frequency and genotype frequency.
• Population-It is freely interbreeding group of
individuals.
• Allele frequency- It is number of individuals
alleles of certain type divided by total number
of alleles of all types in a population.
• Gene locus- It is the portion on chromosome
that representing single gene.

8. Hardy Weinberg
equation
• For example –
• If the frequency of allele ‘A’ in the population is
‘p’ and the frequency of allele “a” in the
population is “q”. Then the frequency of
genotype AA=p² the frequency of genotype
Aa=2pq the frequency of genotype aa= q²
mathematical, p+q=1
• p² + 2pq + q2 = 1

9. ardy Weinberg
quation
Hardy
Weinberg
equation

10. Hardy Weinberg Assumptions
1. Random mating
2. Very large
population
3. Absence of natural
selection
4. No gene flow or
migration
5. No mutation 6. Genetic drift

11. Random
mating
• Organisms mate randomly with
each other, no preference with a
particular genotypes. This type of
mating leads to the resultant
production of the same number of
offspring for all females in a
population which tends to maintain
genetic equilibrium. Hence, to
attain the genetic equilibrium,
random mating should occurring in
the population.

12. Rando
m
mating

13. INFINITE
LARGE
POPULATION
• To maintain the genetic equilibrium
the population should be effectively
infinitely large in size. Because of
that genetic drift is not causing a
random changes in allele
frequencies due to sampling error
from one generation to the next
generation.

14. Natural Selection
Is the differential survival
and reproduction of
individuals due to difference
in the phenotype.
It is a key mechanism of
evolution, the change in the
heritable traits characteristics of
the population over the
generation. Hence, to apply the
Hardy-Weinberg law the natural
selection should be absent.

15. Natural
Selection

16. • Migration is the movement of an organisms
from one place to another with intent to
settle. Causes of migration due to
environmental condition / factors need for
resources due to over population were often
cause migration.
M
Migration/ Gene
flow

17. NO GENE FLOW / MIGRATION
Immigration
Coming into groups/population from
other area.
Emigration
Emigration Leaving habitat area
to move to another area.

18. CONTS.
• Migration is ultimately leads to genes disturbs
in the population.
• It is responsible for adding and deleting the
alleles from the population. Due to gene flow,
population becomes unstable and disturbs the
genetic equilibrium. Hence, migration should
not be present in the population to attains the
Hardy-Weinberg equilibrium.

19. Mutation
• Mutation is the alteration in the nucleotide
sequence in the genome of an organism, virus
or extra-chromosomal DNA. Mutation is the
ultimate source of genetic variation, preventing
populations becoming genetically
homogeneous situations where they otherwise
would.

20. Genetic drift
• Genetic drift :- Genetic drift is a change in the
frequency of an allele within a population over
time. This change in frequency of the allele or
gene variation must occur randomly in order
for genetic drift to occur

21. Use of hardy
Weinberg equilibrium
• 1. Identify the known genotype frequencies.
• 2. Calculate the allele frequencies (p and q).
• 3. Use the allele frequencies to calculate the
expected genotype frequencies.
• 4. Compare the expected and observed
genotype frequencies.

22. Example: A Population
of Flowers
• Scenario: In a population of 100 flowers, 36 are red
(dominant phenotype), and 64 are white(recessive
phenotype). Steps:1. Calculate q² (frequency of white
flowers): q² = 64/100 = 0.64
• 2. Calculate q (frequency of the recessive allele): q = √0.64
= 0.83. Calculate p (frequency of the dominant allele): p = 1
– q = 0.2
• 4. Calculate the expected genotype frequencies: p² = 0.04
(homozygous dominant) 2pq = 0.32 (heterozygous) q² =
0.64 (homozygous recessive)

23. Real-world Examples of
Hardy-Weinberg
Equilibrium and Deviations
• Human populations: Examples of genetic
disorders like cystic fibrosis and sickle cell
anemia. Animal populations: Studies on
populations of birds, insects, and mammals.
• Plant populations: Investigations of flower
color, seed shape, and other traits.

24. Conclusions
• Hardy-Weinberg equilibrium is a powerful
tool for understanding population genetics.
By understanding the assumptions and
limitations of this model, we can gain
insights into the forces shaping the genetic
makeup of populations over time.