Genes 3.1

Genes provide the instructions to build proteins and more besides. The human genome has been decoded by the human genome project and now biologists can search databases to find the location of specific genes. Our understanding of how gene mutations can lead to genetic diseases like sickle cell disease illustrates how genes control our features. The ability to sequence whole genomes allows us to compare the genes in different species and learn more about how they operate.


Key concepts

Learn and test your biological vocabulary for 3.1 Genes using these flashcards 

Essentials - quick revision through the whole topic

These slides summarise the essential understanding and skills in this topic. 
They contain short explanations in text and images - good revision for all students.

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Exam style question about genes

The skill of interpreting DNA sequences alignments is important in this topic.

Answer the question below on a piece of paper, then check your answer with the model answer.

Compare and contrast DNA base sequences shown of three blood group alleles below  [3]

The data comes from a sequence alignment search using the Anagène DNA database.

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Summary list for topic 3.1 Genes

  • Definition of a gene is, "a heritable factor that consists of a length of DNA and influences a specific characteristic."
  • A gene locus is, "the specific position of a gene on a chromosome."
  • Alleles are, "The various specific forms of a gene which differ from each other by one or only a few bases".
  • New alleles are formed by mutation.
  • A genome is, "the whole of the genetic information of an organism."
  • The entire base sequence of human genes was sequenced in the Human Genome Project.
  • The Genbank® database can be used to search for DNA base sequences.

Skills & applications

  • Application to explain: The causes of sickle cell anemia, including a base substitution mutation, subsequent change to the mRNA transcribed from it and a change to the sequence of amino acids in a polypeptide of hemoglobin.
  • Recall of one specific base substitution that causes glutamic acid to be substituted by valine as the sixth amino acid in the hemoglobin polypeptide is required. (Deletions, insertions and frame shift mutations are not needed).
  • Application: Comparison of the number of genes in humans with other species.
    At least one plant and one bacterium should be included in the comparison and at least one species with more genes and one with fewer genes than a human.
    (note: "genome size" is total amount of DNA, not the number of genes in a species).
  • Skill: Use of a database to determine differences in the base sequence of a gene in two species.

Mindmaps

These diagram summaries cover the main details of topic 3.1 Genes.
Study them and draw your own list or concept map, from memory if you can.

Test yourself - multiple choice questions

A quiz containing multiple choice questions covering the understanding and skills outlined in the image above.


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Just for fun

If you want to review key terminology and have some fun with your revision try this Genes card match game. Can you reach the leader board?