Inheritance

Learn about genetic inheritance and the findings of Mendel.

  • Credit: Tim Mitchell

Introduction

We have developed a series of clips to explore the Life Fantastic with your students. The pages are intended for use as a prompt to help you prepare when exploring these topics in lessons. Teachers have told us that the videos and questions best suit being used as a topic introduction.

On this page you will find an overview of the topic covered by the clips, a brief summary of each clip, related questions and how the topic links to the curriculum.  This is one of eight available resources on developmental biology. For more topics see the teaching resources list.

Overview

Topics in the videos

  • Understand that genetic information is transmitted down the generations and the unit of inheritance is the gene
  • Understand that the work of Gregor Mendel and his pea plants was crucial in the discovery of genes as the unit of inheritance
  • Explain how characteristics like hair length and colour can seem to skip generations, because of dominant and recessive genes
  • Explain the terms genotype, phenotype, heterozygous and homozygous

The material in this resource is supported by video clips from the CHRISTMAS LECTURES 2013.

Curriculum links

This resource is suitable for Key Stages 3 and 4 and AS/A2 level. Full curriculum links are given at the bottom of the page.

Clip 1 - How does genetic inheritance work?

With demonstrations involving blue and yellow paint and blue and yellow balls, Alison Woollard unpicks the mechanism of inheritance. This video first considers the now-discredited blending theory of inheritance by using paint to represent the genetic contributions of each parent and asking if it is possible to recreate the parental blue and yellow colours after they have been mixed. Alison next introduces the work of Gregor Mendel and his discoveries on particulate inheritance. Alison proceeds to explain, using the blue and yellow balls as models for alleles of a single gene, how two parents of different phenotype will produce offspring of a single phenotype due to genetic dominance. In the second part of the demonstration Alison reveals how certain phenotypes can be recovered further down the generations as each parent contributes a single set of genes. 

Running Time: 7 min 47 secs

Summary questions

  • Did Mendel’s experiments with pea plants show results similar to the paint or the ball demonstration? (Ball demonstration, 3:39)
  • What is a gene? In the ball demonstration, what represents the alleles? (The different coloured balls, 4:27)
  • In the ball demonstration, which characteristic skips a generation? (Yellow, 6:53)
  • What is the genotype and phenotype of the first generation offspring? (Genotype = where B=blue and b=yellow: Bb; Phenotype = Blue, 5:00)
  • In the ball demonstration, which colour ball represents the dominant gene and which represents the recessive gene? (Dominant=blue, recessive=yellow 5:05)

Questions for discussion 

  • What’s the difference between the genotype and phenotype?
  • What would be the phenotype of offspring of the first cross if the yellow balls were bigger than the blue balls?
  • Huntington’s disease is caused by a dominant allele. Work through the ball demonstration using the example of Huntington’s disease, to find out the chances of a grandchild having Huntington’s if one Grandparent was homozygous for Huntington’s like the blue box in the demo (1st generation: HH x hh -> Hh; 2nd generation: Hh x Hh -> HH, Hh, Hh, hh = 3/4)

Clip 2 - Mendelian inheritance in cats

With the help of a new litter of Oriental cats, Alison Woollard further illustrates the Mendelian mechanism of inheritance. In a real-life example of the previous experiment, Alison asks what the offspring of two short-haired cats will look like. The litter contains a mixture of short- and long-haired kittens. To produce a mixed litter of short and long hair we learn that the adult cats must have had two different coat-length alleles, just like the mixture of blue and yellow balls in the experiment. Like the blue balls, the parent cats have short hair because it is the dominant allele. We also see that there is a mixture of colours in the litter, in a second example of the assortment of genes under Mendelian inheritance.

Running Time: 2 min 34 secs

Summary questions

  • What characteristics can you see in the kittens that are similar to their parents? Which characteristics differ?(Similar: long ears, four legs, tail, two eyes. Differ: short hair vs long hair, yellow vs brown colour)
  • How many kittens have long hair? (three, 1:24) How many have short hair? (five, 1:24)
  • Compare the cats to the ball demonstration. Which colour ball represents long hair and which colour ball represents short hair? (Long hair - yellow ball, short hair - blue ball, 1:35)

Questions for discussion

  • Are there characteristics in you that are similar to your parents? Do you have anything that is different?
  • If hair length is controlled by one gene, is long hair dominant or recessive? (recessive, as the short-haired parents must be carriers to have a litter containing both long and short haired kittens) Does that mean the parents are homozygous or heterozygous?
  • Three kittens have long hair and five have short hair. Given that long hair is recessive (like the yellow balls), what must be the genotype of each of the parents? Use a punnet square and the distribution of phenotypes in the litter to help.

    (Example: Each parent must be heterozygous:

    - S (short)s (long)
    S (short) SS Ss
    s (long) Ss ss

    25% of the litter would be long haired, 3/8 is close to 25%.)

Curriculum links

KS3

Conforming to ‘Genetics and Evolution: Inheritance, chromosomes, DNA and genes’, this resource expands upon the idea that information is transmitted onto the next generation. 

KS4

The clips give a visual demonstration of Mendel’s work and genetic crossing. The concepts of dominant and recessive genes are illustrated by ball colour and coat length in cats. The ball demonstration illustrates the inheritance of characteristics due to different genes and the terms hetero- and homozygosity.

This corresponds to Edexcel GCSE Biology 2BI01/ Science 2SC01 Unit B1 Topic 1 ‘Classification, variation and inheritance’ 1.21-22; AQA GCSE Biology 4401/Science 4405 Unit 1: Biology 1 B1.7.1 ‘Why organisms are so different’ and Biology 4401/Advance Science 4408 Unit 2: Biology 2 B2.7.2 ‘Genetic variation’; OCR GCSE Biology A J243/Science A J241 Unit A161 Module B1 ‘You and your genes’ sections  B1.1 5, B1.2 1-4, 7-8, 12, and B1.3 2 and 4; and in the discussion of inheritance  in AQA GCSE Science B 4450 Unit 2: My Family and Home 3.4.1.3 ‘Human Inheritance and genetic disorders’.

AS/A2

The clips demonstrate the concepts of dominant and recessive genes, hetero- and homozygosity, genotype and phenotype.

Appropriate for AQA GCE Biology A2 2411 Unit 4 BIOL4 ‘Populations and environment’ section 3.4.8; OCR GCE Biology A2 Unit F215 Module 1 ‘Cellular control and variation’ section 5.1.2.

Watch the full lectures

View the full CHRISTMAS LECTURES, Life Fantastic, along with behind the scenes footage, and related content, at the Ri Channel (www.richannel.org).