Genes and hence genetic information is inherited from parents, but the combination of genes inherited from parents by each offspring will be different. In sexual reproduction each parent can only pass on 50% of there genes as the other 50% comes from the second parent.
3.1 Genes
Essential idea: Every living organism inherits a blueprint for life from its parents.
| Statement | Guidance |
3.1.U1 | A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic. |
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3.1.U2 | A gene occupies a specific position on a chromosome. |
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3.1.U3 | The various specific forms of a gene are alleles. |
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3.1.U4 | Alleles differ from each other by one or only a few bases. |
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3.1.U5 | New alleles are formed by mutation. | Deletions, insertions and frame shift mutations do not need to be included. |
3.1.U6 | The genome is the whole of the genetic information of an organism. |
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3.1.U7 | The entire base sequence of human genes was sequenced in the Human Genome Project. |
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3.1.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. | 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. |
3.1.A2 | Comparison of the number of genes in humans with other species. | The number of genes in a species should not be referred to as genome size as this term is used for the total amount of DNA. 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. |
3.1.S1 | Use of a database to determine differences in the base sequence of a gene in two species. | The Genbank® database can be used to search for DNA base sequences. The cytochrome C gene sequence is available for many different organisms and is of particular interest because of its use in reclassifying organisms into three domains. |
3.1 Genes
Essential idea: Every living organism inherits a blueprint for life from its parents.
Syllabus Reference
Chromosome made of DNA and protein
Genes – heritable factors which control specific characteristics
Alleles – different forms of a specific gene
Gene locus – specific position of a gene on a chromosome
All individuals of a species carry the same genes at the same loci on the same chromosomes
3.1 Genes
A gene is a heritable factor that controls or influences a specific characteristic, consisting of a length of DNA occupying a particular position on a chromosome (locus)
3.1.U1 A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic. AND 3.1.U2 A gene occupies a specific position on a chromosome. AND 3.1.U3 The various specific forms of a gene are alleles. AND 3.1.U4 Alleles differ from each other by one or only a few bases.
3.1 Genes
A gene is a heritable factor that controls or influences a specific characteristic, consisting of a length of DNA occupying a particular position on a chromosome (locus)
3.1.U1 A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic. AND 3.1.U2 A gene occupies a specific position on a chromosome. AND 3.1.U3 The various specific forms of a gene are alleles. AND 3.1.U4 Alleles differ from each other by one or only a few bases.
Differing from other alleles by 1 to 2 bases only and occupying the same gene locus as other alleles of the same gene.
3.1 Genes
Allele: One specific form of a gene
3.1.U3 The various specific forms of a gene are alleles. AND 3.1.U4 Alleles differ from each other by one or only a few bases.
3.1 Genes
The genome is the complete set of genetic information
3.1.U6 The genome is the whole of the genetic information of an organism.
It is not just plants such as the grapevine that have large numbers of genes; water fleas are an animal example of an organism with more genes than humans.
When analysing an organisms’ complexity, what other than the count of an organisms’ genes needs to be considered?
Virus
Bacterium
Insect
Bird
Plant
Mammal
3.1 Genes
Humans see themselves as being more complex and evolved than other species.
3.1.A2 Comparison of the number of genes in humans with other species.
3.1 Genes
Humans see themselves as being more complex and evolved than other species.
3.1.A2 Comparison of the number of genes in humans with other species.
3.1 Genes
Allele: One specific form of a gene
3.1.U5 New alleles are formed by mutation.
Genes consist of a certain sequence of DNA bases which can be 100’s to 1000’s bases in length. Usually different alleles of the gene vary by only 1 to 2 of different bases.
3.1 Genes
The allele for Sickle Cell Anemia is created by a mutation of a single nucleotide.
3.1.U5 New alleles are formed by mutation.
This variation when one nucleotide is switched for another is called a single nucleotide polymorphism (SNPs for short)
3.1 Genes
The allele for Sickle Cell Anemia is created by a mutation of a single nucleotide.
3.1.U5 New alleles are formed by mutation.
3.1 Genes
The allele for Sickle Cell Anemia is created by a mutation of a single nucleotide.
3.1.U5 New alleles are formed by mutation.
3.1 Genes
The allele for Sickle Cell Anemia is created by a mutation of a single nucleotide.
3.1.U5 New alleles are formed by mutation.
3.1 Genes
The allele for Sickle Cell Anemia is created by a mutation of a single nucleotide.
3.1.U5 New alleles are formed by mutation.
2 sickle cell alleles
This leads to the production of abnormal red blood cells
Decreased Haemoglobin
Tired and Fatigued
Carrier (1 normal and 1 mutant allele)
This leads to the production of mostly normal red blood cells
Although decreased normal haemoglobin levels decrease the likelihood of malaria surviving
3.1 Genes
The allele for Sickle Cell Anemia is created by a mutation of a single nucleotide.
3.1.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.
Those who only possess the normal blood cell allele do not suffer from sickle cell anaemia but are more susceptible to malaria
Malaria is caused by an endoparasite (Plasmodium falciparum) which reproduces inside red blood cells (but not sickle cells)
3.1 Genes
The allele for Sickle Cell Anemia is created by a mutation of a single nucleotide.
3.1.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.
The Human Genome* Project (HGP) was an international 13-year effort, 1990 to 2003. Primary goals were to discover the complete set of human genes and make them accessible for further biological study, and determine the complete sequence of DNA bases in the human genome.
*The genome is the entire genetic material of an organism. It consists of DNA (or RNA in RNA viruses) and includes both the genes and the non-coding sequences.
3.1 Genes
3.1.U6 The genome is the whole of the genetic information of an organism. AND 3.1.U7 The entire base sequence of human genes was sequenced in the Human Genome Project.
3.1 Genes
“The first methods for sequencing DNA were developed in the mid-1970s. At that time, scientists could sequence only a few base pairs per year, not nearly enough to sequence a single gene, much less the entire human genome. By the time the HGP began in 1990, only a few laboratories had managed to sequence a mere 100,000 bases, and the cost of sequencing remained very high. Since then, technological improvements and automation have increased speed and lowered cost to the point where individual genes can be sequenced routinely, and some labs can sequence well over 100 million bases per year.” (https://www.genome.gov/10001177)
Key advances in technology:
3.1 Genes
Nature of Science: Developments in scientific research follow improvements in technology - gene sequencers are used for the sequencing of genes. (1.8)
One use of aligning base sequences is to determine the differences between species: this can be used to help determine evolutionary relationships.
Your task is to analyse the differences between three or more species (the skill asks for two species, but the online Clustal tool works better with a minimum of three).
For each chosen species retrieve the base sequence:
3.1 Genes
3.1.S1 Use of a database to determine differences in the base sequence of a gene in two species.
Analysis:
To align the sequences:
3.1 Genes
3.1.S1 Use of a database to determine differences in the base sequence of a gene in two species.