Inheritance
In the topic of inheritance it is easy to deliver conflicting information if not carefully planned. Students need to appreciate that for the majority of phenotypic features it is a combination of genes that give rise to this feature, yet in using genetic diagrams (punnett squares) it appears that a single gene codes for a single trait and that there are only two alleles for each gene.
Students often have misconceptions in relation to dominant traits, believing that this is most likely to be found in a population, rather than it being the one expressed over a reccessive trait in a particular individual. It is useful to refer to dominant traits that are rare in populations, such as Achondroplasia and Huntingtons disease.
When using Punnett squares it is important that students understand that these are probabilities and not fixed outcomes. The misconception that students demonstrate is that they believe that if there is a 1 in 4 chance of a couple having a child with a particular condition, if the first child has the condition, the other three will not. It is important to highlight that each child (however many children they have) has a 25% chance of having the condition. This can be linked to explaining sex determination- there is a 50% chance of having a boy or a girl. No matter how many children a couple have, if they have a boy first it does not change the probability of whether the next child will be a boy or a girl.
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Quizzes *suitable for home teaching*
This is a set of four quizzes each with a different theme. The one on inheritance and selection is most relevant for this topic. The quiz contains 20 multiple choice questions and would be a useful homework activity.
Explaining Inheritance
This article describes the stages in discovering that DNA was the molecule responsible for passing on inherited information.
The article can be used as a focus for a small group activity (pairs or threes). You could challenge students to clearly show the sequence of events, and the build-up of evidence, that pointed to DNA being the molecule responsible for inheritance. Listening to discussions provides an opportunity to assess understanding. This activity shows how scientific discoveries build one on the next. It also allows students to practice skills in interpreting and presenting information. Once groups have completed their initial discussion, they can then be mixed to allow students to compare each others’ interpretations. These second discussions can often allow students to tackle any misunderstanding.
There are many ways to make effective use of Catalyst articles such as this. A booklet has been produced which provides ideas on how Catalyst articles can be used with students and includes six exemplar activities.
BBC bite size genetic diagrams
This straight forward explanation of genetic diagrams would be a useful introduction for students to support their understanding of how to predict the results of single gene crosses. This website could be used on a white board, with a careful explanation as a start to the lesson and then left on the board while students complete some exam style single gene cross questions.
BBC bitesize: mendel
This easy to read page would be a useful as pre-reading before this topic was undertaken in class. Students could be provided with this website link for homework, and be tasked with reading through pages 2, 3 and 4 and then completing the “test bite” the link for which is at the bottom of page 4
Characteristics of Inheritance
There are a number of animations on this weblink which students could review through independent study. The animations are tours of the basics of inheritance and visually demonstrate how chromosomes and traits are inherited from parents.
Groups or pairs of students could be assigned a particular animation to review and then could feedback to their peers on what they learnt from the animation.
Animations suitable for this group work activity would be the 6 tours listed under "Tour of basic genetics".
Students could then be asked to read the "What are dominant and recessive?" information provided in the Characteristics of inheritance section.
There are a range of other useful pages on this weblink that students could use as independent study or that cold be used in class--for example the pigeonetics. When using this however it is important to stress that bird sex determination is different to sex determination in humans