T – Vestigal
Test tube B
F1 generation
F1 ratio: 1:2:1
Key:
B= Normal body
B = Black body
T = normal wings
T – Vestigal
F2 generation
F2 Ratio: 9:3:3:1
Key:
B= Normal body
B = Black body
T = normal wings
T – Vestigal
Explain dihybrid patterns using initial research done by Mendel (M18.1b)
Dihybrid inheritance refers to the continuous inheritance of two characters. In one of Mendel experiments he carried out studies on seed shape (round vs. wrinkled) and seed colour (yellow vs. green) together as one investigation. During his previous experiment (monohybrid cross) Mendel knew that round seeds were dominant to wrinkled seeds and yellow seeds were dominant to green seeds. He decided to cross plants with both dominant features and receive features. F1 generation yielded plant of round, yellow seeds- dominant features.
Mendel’s results
Results
Round yellow: 9
Round green: 3
Wrinkled yellow: 3
Wrinkled green: 1
This results show the research Mendel conducted, when he raised f1 generation seeds and allowed them to pollinate. He gathered the seeds. Out of 556 seeds produced, majority of 315 possessed two dominant gene- round yellow, the other group possessed 32 seeds which had two receive gene, 209 possessed features not previously found and 108 possessed both dominant and receive gene.
Though Mendel research on dihybrid crossing did not match his previous research (monohybrid cross) it still showed the significant ratio: 3:1.
On the biases of his findings Mendel produced his second law which stated: Each pair of contrasted characters may be combined with either of another pair
In other words, each pair of allelic member may combine together to form another pair. Through the use of Mendel law it has helped me achieve my observed results and compared the observed result with from Mendel law and results from his experiment.
You then need to analyze the pattern seen in the expected results and the observed results i.e. do they follow the same pattern, if they don’t then how do you explain the difference in the patterns (HINT: think about the work you did with meiosis.) (D18.1b)
Observed results
Males in tube A
8 Normal body, normal wings
4 Normal body, vestigal wings
2 Black body, normal wings
1Black body, vestigal wings
Expected
9: normal body, normal wings
3: normal body, vestigal wings
3: black body, normal wings
1: black body, vestigal
Difference
The expected values from my experiment had tiny amount of difference from the 9:3:3:1 ration. Possible reasons for difference from expected result could be due to an error done during my experiment. The other reason could be during meiosis, though, my results for male test tube A differed slightly from expected result, but it still followed Mendel’s 2nd law of inheritance (3:1 ratio).
Males in 2nd tube
4 Normal body, Normal wings
2 Normal body, vestigal wings
3 black body, normal wings
0 black body, normal wings
Expected
9: normal body, normal wings
3: normal body, vestigal wings
3: black body, normal wings
1: black body, vestigal
Difference
The expected values from my experiment had large amount of difference from the 9:3:3:1 ration. Possible reasons for difference from expected result could be due to an error done during my experiment. The other reason could be during meiosis, pairs of homologues chromosomes assemble themselves randomly on the equator of the spindle during metaphase 1 of meiosis, though each pair has the same general features, they differ in the detail of these features. Another possibility could be, during prophase 1 of meiosis, equal portions of homologous chromosomes may be exchanged to produce new genetic combinations and the separation of linked genes
The observed result does not match with Mendel’s 2nd law of inheritance (3:1 ratio).
Females in tube A
10 normal body, normal wings
3 normal body, vestigal wings
5 black body, normal wings
1 black body, vestigal wings
Expected
9: normal body, normal wings
3: normal body, vestigal wings
3: black body, normal wings
1: black body, vestigal
Difference
The expected values from my experiment had tiny amount of difference from the 9:3:3:1 ration. Possible reasons for difference from expected result could be due to an error done during my experiment. Possible reason could be during meiosis, though, my results for female test tube A differed slightly from expected result, but it still followed Mendel’s 2nd law of inheritance (3:1 ratio).
Females in test tube B
5 normal body, normal wings
2 normal body, vestigal wings
0 black body, normal wings
1 black body, vestigal wings
Expected
9: normal body, normal wings
3: normal body, vestigal wings
3: black body, normal wings
1: black body, vestigal
Difference
The expected values from my experiment had large amount of difference from the Mendel’s 9:3:3:1 ration. Possible reasons for difference from expected result could be due to an error done during my experiment. The other reason could be during meiosis, pairs of homologues chromosomes assemble themselves randomly on the equator of the spindle during metaphase 1 of meiosis, though each pair has the same general features, they differ in the detail of these features. Another possibility could be, during prophase 1 of meiosis, equal portions of homologous chromosomes may be exchanged to produce new genetic combinations and the separation of linked genes.
The observed result does not match with Mendel’s 2nd law of inheritance (3:1 ratio).
Using the processes of mutation you need to explain how this process can lead to evolutionary change. That is how can mutation occur and how this can make new species or changes in species. (D18.1a)
Brief introduction of evolution theory
This theory was published by Darwin in 1859; since it was published, research modification has been added to his theory.
Variation: - he argued in any population of organism that sexually reproduces, there is variation in each person. The results of this variation are environmental differences and inherited variation.
Competition: - Organisms reproduce much more than the world can cope with, so there is competition of food and resources.
Natural selection: - In this, Darwin argued that organisms that were best able to fight or escape predation would be more likely to survive. They would reproduce and parent the next generation. If their dominant characteristics were inherited, the result of this would be the next generation inheriting the dominate gene and are genetically capable of surviving. For example, an animal which is incapable of finding resource to survive is less likely to reproduce large number of offspring’s
Gene mutation
A gene is a long strand of DNA that codes the reproduction of proteins. A spontaneous change in the DNA sequence is called gene mutation. All genes mutate at slow rate but it can be increase if the living organism is exposed to mutagens, such as, radiation or chemicals. Most mutagens are very harmful to living organisms, but some give the organism an advantage over other living organism, for example a mutation giving rats resistance to warfarin, rat poison. This gives the possessor an advantage to other rats. This mutation can be passed on to next generation making the more surviving in the future.
Gene mutation can occur in two ways: gene mutation can be inherited from your father or mother during their life time; mutations passed on from parent to child are called hereditary mutation. Gene mutations that take place in only sperm or egg cells are called De novo mutations.
De novo mutations are thought to be the possible cause of genetic disorders in which a child is affect genetic disorder but has no history of family disorders. Mutations that occur in parents DNA during parent life time could have been acquired through environment changes such as ultraviolet radiation from sun, and mistakes in gene copy during cell division. Gene mutation acquired from cells other than sperm or eggs cells can not be passed on to next generation. Mutation can also occur in a single cell within an embryo, when the cell is dividing during growth and development; the individual will have genes cells and genes with no genetic change. This process is called mosacism. Genetic changes that occur in more than 1% of population are called polymorphisms. There are so common that there are considered as gene variation in DNA. Polymorphisms are the cause of differences such as; eye colour, hair colour and blood type. They have no known negative effects on an individual but other types of mutation such as de novo mutation or heredity mutation can influence risk of developing disorders. Gene mutation can cause alteration during the making of protein and ultimately, cause the protein to malfunction. Proteins are the main component in body tissue and help build, repair muscles, tissues and increase strength of an individual; malfunction of the protein could cause medical disorders such as cystic fibrosis.
Bibliographies
Biological Sciences’ by (Author), (Author), (Author)
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