Topic: Protein case study
July 17, 2019 / By Ofer Question:
1)Suggest two factors that might cause mutations
2) Mutations that are passed on to the next generation may have an effect in the offspring, or no effecr at all. Explain how a mutation could cause the following results
i) no effect ..........................
ii) a harmful effect.................
iii) a positive effect.......................
Any input would be great
Lauren | 8 days ago
1) Two classes of mutations are spontaneous mutations (molecular decay) and induced mutations caused by mutagens.
i. Spontaneous mutations on the molecular level include:
Tautomerism – A base is changed by the repositioning of a hydrogen atom.
Depurination – Loss of a purine base (A or G) to form an apurinic site (AP site).
Deamination – Changes a normal base to an atypical base. Examples include C → U and A → HX (hypoxanthine), which can be corrected by DNA repair mechanisms; and 5MeC (5-methylcytosine) → T, which is less likely to be detected as a mutation because thymine is a normal DNA base.
Transition – A purine changes to another purine, or a pyrimidine to a pyrimidine.
Transversion – A purine becomes a pyrimidine, or vice versa.
ii. Induced mutations on the molecular level can be caused by:
Base analogs (e.g. BrdU)
Alkylating agents (e.g. N-ethyl-N-nitrosourea) These agents can mutate both replicating and non-replicating DNA. In contrast, a base analog can only mutate the DNA when the analog is incorporated in replicating the DNA. Each of these classes of chemical mutagens has certain effects that then lead to transitions, transversions, or deletions.
Agents that form DNA adducts (e.g. ochratoxin A metabolites)
DNA intercalating agents (e.g. ethidium bromide)
Ultraviolet radiation (nonionizing radiation). Two nucleotide bases in DNA – cytosine and thymine – are most vulnerable to radiation that can change their properties. UV light can induce adjacent thymine bases in a DNA strand to pair with each other, as a bulky dimer.
DNA has so-called hotspots, where mutations occur up to 100 times more frequently than the normal mutation rate. A hotspot can be at an unusual base, e.g., 5-methylcytosine.
Mutation rates also vary across species. Evolutionary biologists have theorized that higher mutation rates are beneficial in some situations, because they allow organisms to evolve and therefore adapt more quickly to their environments. For example, repeated exposure of bacteria to antibiotics, and selection of resistant mutants, can result in the selection of bacteria that have a much higher mutation rate than the original population (mutator strains).
i. there are an effect when make a mutation.. so no answer for this..
ii. Harmful effect
Changes in DNA caused by mutation can cause errors in protein sequence, creating partially or completely non-functional proteins. To function correctly, each cell depends on thousands of proteins to function in the right places at the right times. When a mutation alters a protein that plays a critical role in the body, a medical condition can result. A condition caused by mutations in one or more genes is called a genetic disorder. Some mutations alter a gene's DNA base sequence but do not change the function of the protein made by the gene. Studies in the fly Drosophila melanogaster suggest that if a mutation does change a protein, this will probably be harmful, with about 70 percent of these mutations having damaging effects, and the remainder being either neutral or weakly beneficial.
If a mutation is present in a germ cell, it can give rise to offspring that carries the mutation in all of its cells. This is the case in hereditary diseases. On the other hand, a mutation can occur in a somatic cell of an organism. Such mutations will be present in all descendants of this cell, and certain mutations can cause the cell to become malignant, and thus cause cancer.
Often, gene mutations that could cause a genetic disorder are repaired by the DNA repair system of the cell. Each cell has a number of pathways through which enzymes recognize and repair mistakes in DNA. Because DNA can be damaged or mutated in many ways, the process of DNA repair is an important way in which the body protects itself from disease.
iii. Positive effect
Although many mutations are deleterious, mutations may have a positive effect given certain selective pressures in a population.
For example, a specific 32 base pair deletion in human CCR5 (CCR5-Δ32) confers HIV resistance to homozygotes and delays AIDS onset in heterozygotes. The CCR5 mutation is more common in those of European descent. One theory for the etiology of the relatively high frequency of CCR5-Δ32 in the European population is that it conferred resistance to the bubonic plague in mid-14th century Europe. People who had this mutation were able to survive infection; thus, its frequency in the population increased. It could also explain why this mutation is not found in Africa where the bubonic plague never reached. Newer theory says the selective pressure on the CCR5 Delta 32 mutation has been caused by smallpox instead of the bubonic plague.
Originally Answered: Atomic species, molecular species or extensive 3-D structures?
The metals are going to be extensive 3-D, since their structure at room temperature (RT) consist of a huge crystalline lattice with the atoms on the crystal vertices. That means Mg and Cs are definitely in this category. Carbon is also an extensive 3-D, since either as diamond or graphite, their structure consists of a very large number of C connected to each other through covalent bonds.
Also at RT, oxygen is a molecular species: it consists of molecules O2.
Neon is atomic. But you could also say it is molecular. The Ne species are in the gas phase, single atoms moving like free particles, but you could also say their are "monoatomic molecules".
The others I'd say are a combination of molecular + extensive 3-D at RT. Phosphorous (at least one of its form) is made of molecules, like P4, Iodine molecules like I2, Sulfur molecules S8. Therefore, in this sense, they're molecular. However, at RT, these molecules are not totally disconnected from each other. These elements are solids at RT and each one of their molecular species are connected to others by van der Waals type of forces and are positioned somewhat like an endless crystal, or non-crystalline solid arrangement, but with no specific "ending". Therefore, their 'extensive 3D structures'.
Two great answers so far. rAY's answer in particular is spectacular.
I just wanted to comment on the first three words of your question ... "Producing new species .." I hope you are not under the misunderstanding that mutations=evolution and evolution=speciation. It is necessary to understand why small changes (mutations) appear and then propagate in a species before we understand how enough of these can result in *speciation* (the split of a species into two species).
Mutations are just the first *tiny* step in this process. But a mutation by itself is NOT evolution, much less speciation. Evolution cannot be said to occur until that mutation *spreads* into the population, through genetic drift, or natural selection. And only after *many* generations of *many* mutations accumulating differently in two different subpopulations of a species, can the two subpopulations be said to be separate *species* ... because they have accumulated so many genetic differences that they are no longer able to interbreed.
In other words, the headline of your question felt a little jarring ... jumping from "producing new species" to asking about the factors that cause mutations. It is a bit like headlining a question "About auto mechanics ..", but then asking a question about how gasoline burns. It's certainly a valid question ... but it is such a small part about explaining the topic of the headline.
It's all about X and Y chromosomes. A female will have two X chromosomes and a male will have one X and one Y. These are known as the sex chromosomes, which determine the sex in the species. This occurred from mutations of the chromosomes in the simple species at the beginning of evolution and since those species have evolved, the recessive and dominant factors of these chromosomes has produced countless males and females.
Mutations can be caused by strong chemicals or radiation; chance also plays a part.
1) no effect: a change in human eye color
2) a harmful effect: the gene which produces a digestive protease in a carnivore no longer makes a functioning enzyme
3) a positive effect: the gene that produces chlorophyll in a plant produces a pigment able to absorb a wider range of light wavelengths.