3.1: Genes

Key vocabulary

Essential idea: Every living organism inherits a blueprint for life from its parents.

U1: A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic.

U2: A gene occupies a specific position on a chromosome.

U3: The various specific forms of a gene are alleles.

U4: Alleles differ from each other by one or only a few bases.

U5: New alleles are formed by mutation. Guidance from the syllabus: Deletions, insertions and frame shift mutations do not need to be included.

U6: The genome is the whole of the genetic information of an organism.

A1: The causes of sickle cell anemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in hemoglobin. Guidance from the syllabus: Students should be able to recall one specific base substitution that causes glutamic acid to be substituted by valine as the sixth amino acid in the hemoglobin polypeptide.

Exercise 3: watch the animation below and answer the following questions:

• What causes the symptoms of sickle cell anaemia?

• Mutations in which gene cause these symptoms?

• What is the specific base substitution mutation which creates the sickle cell allele? What is the difference between the normal allele and the sickle cell allele?

• What is the corresponding change in the mRNA sequence?

• What is the corresponding change in the translated amino acid sequence?

NoS: Developments in scientific research follow improvements in technology—gene sequencers are used for the sequencing of genes. (1.8)

U7: The entire base sequence of human genes was sequenced in the Human Genome Project.

Exercise 4: Using the resource linked on this page, describe the human genome project and it's outcomes.