3.1 Genes

State the number of genes in the human genome: Application: Comparison of the number of genes in humans with other species.

There are an estimated 20,000 - 25,000 genes in the human genome.

Outline two outcomes of the Human Genome Project: Understanding: The entire base sequence of human genes was sequenced in the Human Genome Project.

- The Human Genome Project identified the number, location, size and sequence of the human genome. - Allowed for the production of specific gene probes to detect carriers of genetic diseases.

Describe a base substitution mutation: Understanding: New alleles are formed by mutation.

A base substitution mutation occurs replaces one base in a gene with another. The new allele that results from the mutation might: cause a small change in the protein produced by the gene, have no effect on the protein produced by the gene, cause an incomplete non-functioning protein to form.

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

A gene is a sequence of DNA on a chromosome that codes for a particular characteristic and can be inherited.

Define gene locus: Understanding: A gene occupies a specific position on a chromosome.

A gene locus is the location of a gene on a chromosome.

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

A genome is a complete set of genes present in an organism.

Define "sequence" in relation to genes/genomes: Understanding: The entire base sequence of human genes was sequenced in the Human Genome Project.

A sequence is the order of nitrogenous bases in a gene or a genome.

Define alleles: Understanding: The various specific forms of a gene are alleles.

Alleles are alternative forms of a gene that code for the different variations of a specific characteristic. (ex: eye color is a gene and alleles are the colors)

State a similarity between alleles of the same gene: Understanding: The various specific forms of a gene are alleles.

Alleles of the same gene are found at the same locus on homologous chromosomes, have mostly the same nucleotide sequence and code for the same type of protein.

State the difference between alleles of the same gene: Understanding: Alleles differ from each other by one or only a few bases.

Alleles of the same gene differ from other alleles in the nucleotide sequence by one or a few bases.

Define gene mutation: Understanding: New alleles are formed by mutation.

Gene mutation is an alteration in the DNA sequence of a gene.

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

The Human Genome Project aimed to determine the sequence of the complete human genome and the order of all the bases in human DNA.

Base substitution mutation in sickle cell disease: Understanding: New alleles are formed by mutation.

The base substitution mutation of GAG into GTG in the sequence of haemoglobin causes an incorrect amino acid to be translated into the protein. This leads to a malformation of red blood cells and results in sickle cell disease.

State the size in base pairs of the human genome: Understanding: The genome is the whole of the genetic information of an organism.

The human genome is composed of about 3.2 billion base pairs organized into 23 paired chromosomes.