# A Level Biology: Lesson 296.

# The Hardy-Weinberg Principle

## Task 1. Check Where this Lesson fits into your Exam Specification!

## Task 2. Watch the Revision Notes Lessons in Full.

00:00 Intro Screen

00:40 Learning Outcomes

01:00 The Hardy-Weinberg Equation

01:06 Punnett and Hardy

02:24 Monohybrid Cross (Brachydactyly)

05:28 What does the Hardy-Weinberg Principle state?

05:45 What are the Rules?

06:23 A population of Rabbits...

14:17 p's and q's

16:52 What does all this tell us?

00:00 Intro Screen / Learning Outcomes

00:18 in the previous lesson

00:42 Brachydactyly Punnett Square

00:56 - We need to recap some key terms

01:10 Definition 1. Population

01:27 Definition 2. Phenotype

01:38 Definition 3. Genotype (Homozygous Dominant, Heterozygous and Homozygous Recessive).

02:26 Definition 4. Gene Pool

02:55 Definition 5. Allele Frequency

03:36 Hardy-Weinberg Exam Style Q and A (1).

08:48 Hardy-Weinberg Exam Style Q and A (2).

12:04 Hardy-Weinberg Exam Style Q and A (3).

14:38 Hardy-Weinberg Exam Style Q and A (4).

★ AQA Specification Reference: - 3.7.1 Inheritance (A-level only). In a diploid organism, the alleles at a specific locus may be either homozygous or heterozygous. Monohybrid and cross involving dominant, recessive and alleles. Students could use information to represent phenotypic ratios in monohybrid crosses. Students could show understanding of the probability associated with inheritance. 3.7.2 Populations (A-level only). The Hardy–Weinberg principle provides a mathematical model, which predicts that allele frequencies will not change from generation to generation. The conditions under which the principle applies. The frequency of alleles, genotypes and phenotypes in a population can be calculated using the Hardy–Weinberg equation. Students could collect data about the frequency of observable phenotypes within a single population. Students could calculate allele, genotype and phenotype frequencies from appropriate data using the Hardy–Weinberg equation.

★ CIE Specification Reference: - 17.2 Natural and artificial: d) Use the Hardy–Weinberg principle to calculate allele, genotype and phenotype frequencies in populations and explain situations when this principle does not apply selection.

★ Edexcel (Biology A – Salters-Nuffield) Specification Reference: - Topic 2: Genes and Health. 2.13 i) Know the meaning of the terms: gene, allele, genotype, phenotype, recessive, dominant, homozygote and heterozygote. ii) Understand patterns of inheritance, including the interpretation of monohybrid inheritance. Topic 4: Biodiversity and Natural Resources: 4.5 i) Understand how the Hardy-Weinberg equation can be used to see whether a change in allele frequency is occurring in a population over time.

★ Edexcel (Biology B) Specification Reference: - 8.2 Transfer of genetic information: Understand the terms ‘genotype and phenotype’,’ homozygote and heterozygote’, ‘dominance’, ‘recessive’. Be able to construct genetic crosses. 8.3 Gene pools - Understand how the Hardy-Weinberg equation can be used to monitor changes in the allele frequencies in a population.

★ OCR (Biology A) Specification Reference: - 6.1.2 Patterns of inheritance. (f) the use of the Hardy–Weinberg principle to calculate allele frequencies in populations. The equations for the Hardy–Weinberg principle will be provided where needed in assessments and do not need to be recalled.

★ OCR (Biology B) Specification Reference: - 5.1.2 Population genetics and epigenetics. (c) the use of Hardy-Weinberg equations to analyse changes in allele frequencies in populations. The equations for the Hardy-Weinberg principle will be provided where needed in assessments and do not need to be recalled.

★ WJEC Specification Reference: - Continuity of Life: 6. Variation and evolution. (g) the use of the Hardy-Weinberg principle and equation. (h) the conditions under which the Hardy-Weinberg principle applies.