Malignant tumors are classified according to the type of cells that give rise to them.
Three reasons a species could become extinct include, deforestation, being overhunted, not enough food available.
• Homologous structures: Both Ostriches have wings similar in form to those of their ancestors, but that do not allow the birds to fly.
Homologous structures are those that have structural similarities but are different in function. For example, if we look at the anatomical structure of a bird’s wing, it is very similar in structure with a human arm. However, over the course of time they have evolved to perform different functions.
• Vestigial structures: The inner ear bones of mammals have evolved from bones that form the jaws of reptiles.
Vestigiality refers to the process in which some structure lose their function over the course of evolution in some specie but they are functionally normal in other species. Such a structure is the inner ear bones of mammals which donot perform an important function in mammals but do perform in reptiles.
• DNA sequence data: Both Genes involved in RNA replication are conserved among bacteria and animals, suggesting a common evolutionary origin.
The sequencing of genetic data is an excellent method of finding the evolutionary histories and relatedness of different organisms. This field of sciences is called phylogenetics and the mentioned example is the result of phylogenetics.
• Analogous structures: The jointed legs of insects and vertebrates arose independently, indicating a different evolutionary origin.
Analogous structures are those that have similar function but they look very different in structure or anatomy. This is because they have been evolved from different ancestors and perform different functions. One example of these structures is mentioned, The jointed legs of insects and vertebrates that look different bur perform same function.
Answer and Explanation:
The Huntington disease is caused by a mutation in the gene that codifies for the Huntingtin protein (Htt). The mutation produces an altered form of the protein leading to the neuron´s death in certain areas of the brain.
The Huntington disease characterizes for being,
- Hereditary, passing from generation to generation. To express the disease, a person must have been born with an altered gene.
- Autosomal, affecting men and women equally, because the mutated gene is located on an autosomal chromosome.
- Dominant, which means that by getting only one copy of the altered gene coming from any of the parents, the receiving person will express the disease. The mutation in the gene dominates over the normal gene copy.
- Expressed by heterozygosis. Most people affected by the disease are heterozygous, with a normal copy and a mutated copy.
There are just a few cases all around the world (3% approximately) in which the disease is expressed with no family history. The progenitors are not affected by the mutation. These cases are very rare and are called <u>"de-novo" mutations.</u> A new mutation is spontaneously produced and it is not inherited from any of the parentals. It consists of an increase in the number of CAG repetitions. In a normal person, the number of CAG repetitions is less than 35. When there are 40 or more repetitions it occurs the disease. But when there are between 35 and 39 repetitions, the penetrance of the disease is incomplete. This is a "gray zone". Those alleles that fall in the gray zone are unstable and might produce the HD. Individuals with these unstable alleles have a tendency to increase the number of repetitions from generation to generation until the number reaches 40 repetitions and the person expresses the disease. This <u>usually occurs in the paternal germinal line</u>, as it is particularly unstable in sperm and probably meiosis greatly affects their instability, causing an increase in the number of CAG repeats.
I think the answer is B
Beacuse It follows the successful completion of S phase, during which the cell's DNA is replicated. Mitosis is a part of the cell cycle process by which chromosomes in a cell nucleus are separated into two identical sets of chromosomes, each in its own nucleus.
