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B6 H) Variation & Mutations
B6 H) Variation & Mutations
Mutations
A mutation is a random change in an organism’s DNA/ genome (genome is the entire genetic material of an organism). A mutation alters a gene, which leads to a genetic variant (a different version of the same gene). Genes give the instructions for arranging the amino acids to make a protein. A mutation causing a different genetic variant for a gene will result in the amino acids being put together in a different order, which will lead to changes in the protein that the gene codes for.
Most of the genetic variants caused by mutations will have no effect on the phenotype (the phenotype is the physical characteristic that the individual displays). The protein that the mutated gene produces works just as well as the protein produced by the non-mutated gene.
Some of the genetic variants caused by mutations will have a small effect on the phenotype of an individual. For example, eye colour is determined by more than one gene. If there was a mutation on one of the genes that contributes to eye colour, the eye colour of an individual may change a little bit but not by a huge amount; the phenotype will be changed very slightly. Hair colour is also controlled by multiple genes so a mutation on one of the genes that contributes to hair colour would also result in a slight change in hair colour; the phenotype will change very slightly.
Sometimes and very rarely, the genetic variant produced by the mutation has a huge effect on the phenotype. An example is the mutation that causes cystic fibrosis. The gene codes for a protein that produces mucus, sweat and digestive juices. The gene also controls the movement of salt and water in and out of cells. The mutated cystic fibrosis gene means that the protein produced does not work properly. This results in excess mucus that is thicker and stickier than normal mucus being produced in the lungs and the digestive system. This mucus makes it difficult for individuals with cystic fibrosis to breath and digest food.
A mutation is a random change in an organism’s DNA/ genome (genome is the entire genetic material of an organism). A mutation alters a gene, which leads to a genetic variant (a different version of the same gene). Genes give the instructions for arranging the amino acids to make a protein. A mutation causing a different genetic variant for a gene will result in the amino acids being put together in a different order, which will lead to changes in the protein that the gene codes for.
Most of the genetic variants caused by mutations will have no effect on the phenotype (the phenotype is the physical characteristic that the individual displays). The protein that the mutated gene produces works just as well as the protein produced by the non-mutated gene.
Some of the genetic variants caused by mutations will have a small effect on the phenotype of an individual. For example, eye colour is determined by more than one gene. If there was a mutation on one of the genes that contributes to eye colour, the eye colour of an individual may change a little bit but not by a huge amount; the phenotype will be changed very slightly. Hair colour is also controlled by multiple genes so a mutation on one of the genes that contributes to hair colour would also result in a slight change in hair colour; the phenotype will change very slightly.
Sometimes and very rarely, the genetic variant produced by the mutation has a huge effect on the phenotype. An example is the mutation that causes cystic fibrosis. The gene codes for a protein that produces mucus, sweat and digestive juices. The gene also controls the movement of salt and water in and out of cells. The mutated cystic fibrosis gene means that the protein produced does not work properly. This results in excess mucus that is thicker and stickier than normal mucus being produced in the lungs and the digestive system. This mucus makes it difficult for individuals with cystic fibrosis to breath and digest food.
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Genes & Variation
Individuals within a species vary. For example, we are all of different heights, we all have different facial characteristics etc… The characteristics that we display are known as the phenotype (phenotype starts with a P, so use the P to think Physical characteristics). There are two different reasons for this variation.
Genetic Factors
One of the reasons for the variation between individuals is due to differences in the genetic material that we contain. The entire genetic material of an organism is known as the genome and all humans have different genomes (except for identical twins or triplets etc.). All of the genetic information of organisms is stored as DNA in the nucleus of cells. DNA can be arranged in chromosomes and humans have 23 pairs of chromosomes (which is 46 chromosomes in total). A gene is a small section of DNA that determines a particular feature. Genes determine a particular feature because they tell the cell the order to put the amino acids in to make a protein, which leads to the development of that particular feature. Individuals have different genes, which means that they have different genomes, thus meaning that they have different genotypes and phenotypes. This is why hair colour, eye colour and facial features vary between individuals.
Environmental Factors
The second reason for variation between individuals in a population is environmental factors. For example, how much nutrients and food individuals eat will determine the development of individuals; if a baby does not receive sufficient nutrients when it is young, it will likely mean that the baby will not develop and grow correctly. Also, if a plant does not have access to light, plenty of carbon dioxide and nutrients, it will likely have stunted growth and maybe even some deficiency diseases.
Most of the variation between individuals is determined by a combination of genetic and environmental factors.
Individuals within a species vary. For example, we are all of different heights, we all have different facial characteristics etc… The characteristics that we display are known as the phenotype (phenotype starts with a P, so use the P to think Physical characteristics). There are two different reasons for this variation.
Genetic Factors
One of the reasons for the variation between individuals is due to differences in the genetic material that we contain. The entire genetic material of an organism is known as the genome and all humans have different genomes (except for identical twins or triplets etc.). All of the genetic information of organisms is stored as DNA in the nucleus of cells. DNA can be arranged in chromosomes and humans have 23 pairs of chromosomes (which is 46 chromosomes in total). A gene is a small section of DNA that determines a particular feature. Genes determine a particular feature because they tell the cell the order to put the amino acids in to make a protein, which leads to the development of that particular feature. Individuals have different genes, which means that they have different genomes, thus meaning that they have different genotypes and phenotypes. This is why hair colour, eye colour and facial features vary between individuals.
Environmental Factors
The second reason for variation between individuals in a population is environmental factors. For example, how much nutrients and food individuals eat will determine the development of individuals; if a baby does not receive sufficient nutrients when it is young, it will likely mean that the baby will not develop and grow correctly. Also, if a plant does not have access to light, plenty of carbon dioxide and nutrients, it will likely have stunted growth and maybe even some deficiency diseases.
Most of the variation between individuals is determined by a combination of genetic and environmental factors.
Discontinuous & Continuous Variation
Variation between individuals can be measured with two different types of variables; discontinuous and continuous.
Discontinuous variation is where the variation of a particular characteristic (phenotype) can be split into two or more distinct categories and each individual falls into exactly one of these categories (they can never appear in more than one category). An example of discontinuous variation is blood group. There are 4 distinct blood groups; A, B, AB and O. An individual will be in only 1 of these 4 blood groups; you cannot be in none or more than 1 of these blood groups.
Continuous variation is where the phenotype of individuals varies within a range and there are no categories. Examples of continuous variation are an individual’s height and mass. Both of these can take a wide range of values. For example, with height, you could be 165 cm, or 186.52 cm, or 192.76212 cm etc….
Characteristics that are of discontinuous variation tend to be determined solely by genetic factors and not by environmental factors. In our example, blood group is determined by our genes, and it is not influenced by environmental factors (your blood group will remain the same irrespective of the environment that you are in). Whereas, characteristics that are of continuous variation tend to be influenced by both genetic and environmental factors. For example, height is dependent on genetics and the environment that you are in.
Variation between individuals can be measured with two different types of variables; discontinuous and continuous.
Discontinuous variation is where the variation of a particular characteristic (phenotype) can be split into two or more distinct categories and each individual falls into exactly one of these categories (they can never appear in more than one category). An example of discontinuous variation is blood group. There are 4 distinct blood groups; A, B, AB and O. An individual will be in only 1 of these 4 blood groups; you cannot be in none or more than 1 of these blood groups.
Continuous variation is where the phenotype of individuals varies within a range and there are no categories. Examples of continuous variation are an individual’s height and mass. Both of these can take a wide range of values. For example, with height, you could be 165 cm, or 186.52 cm, or 192.76212 cm etc….
Characteristics that are of discontinuous variation tend to be determined solely by genetic factors and not by environmental factors. In our example, blood group is determined by our genes, and it is not influenced by environmental factors (your blood group will remain the same irrespective of the environment that you are in). Whereas, characteristics that are of continuous variation tend to be influenced by both genetic and environmental factors. For example, height is dependent on genetics and the environment that you are in.
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