Answer:
(a) crossing over: Meiosis I, Recombination
(b) chromatids separate at their centromeres and migrate to opposite poles: Meiosis II, Anaphase II
(c) chromosomes become aligned in pairs at the equator: Meiosis II, Metaphase II
Explanation:
Homologous recombination is a type of genetic recombination that occurs during meiosis (formation of ovum and sperm cells). The paired chromosomes of the male and female parents are aligned so that similar DNA sequences intersect. This crossing over produces an exchange of genetic material, which is an important cause of the genetic variability observed in the offspring.
Meiosis II: Anaphase II. The centromeres separate and the daughter chromatids - now individual chromosomes - move to the opposite poles of the cell. The centromeres separate, and the two chromatids of each chromosome move toward the opposite poles in the spindle.
Meiosis II: Metaphase II. Chromosomes are accommodated in the equatorial plate of metaphase, similar to what happens in mitosis. They are attached to the already fully formed meiotic spindle. Each chromosome is aligned in the equatorial plate of the metaphase, as it happens in mitosis.
Answer:
I, II, III
Explanation:
A threshold stimulus is a stimulus that is capable to produce a response in excitable tissues such as neurons and muscle fibers. At threshold potential, the outward movement of K+ and inward movement of Na+ become equal to each other. When the potential exceeds the threshold potential, more and more Na+ enter the cell to depolarize it and to allow the opening of Na+ channels. Therefore, to fire an action potential, the threshold must be exceeded.
Conduction of action potential is all or none phenomenon which means that either it occurs or it does not occur. As an impulse is passed by each successive part of an exon, it enters the refractory period during which there is no conduction of nerve impulse. It ensures the one-way conduction of impulse from the cell body to the axon terminal only.
Answer:
<u>Polygenic therapies are more likely to show </u><u>unintended effects</u><u> in other regions of the genome likely resulting in harmful diseases.</u>
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Explanation:
Gene therapy involves biotechnological techniques that add or remove gene sequences in the genome. These are typically used in eliminating harmful genes that cause genetic diseases or disorders and are generally thought to improve an individual's quality of life.
Polygenic traits are controlled by several genes. Similarly, polygenic diseases may be caused by variations in several gene sequences. These include hypertension, heart disease, and diabetes. Polygenic therapies are more likely to show unintended effects in other regions of the genome, leading to other deleterious disease-causing effects.
Answer:
a) There are lots of genes on chromosome 1 could be affected, and the gametes could be imbalanced (missing segments of DNA or whole chromosomes)
b) Roughly 50%
c) No. I would advise that the couple undergo preimplantation genetic diagnosis, so that a zygote carrying the normal copy of chromosome 1 could be selected.
Explanation:
Chromosome 1 is one of the largest and most gene rich chromosomes. An inversion that covers 70% of its length would cover lots of genes.
While an inversion on its own would not seem problematic (as all the genes on the chromosome are still there), when it comes to meiosis, the sister chromatids would not be able to correctly align, and crossing over would further complicate this. It could also lead to unbalanced gametes missing entire parts of the chromosome. Therefore, there are likely numerous genes that will be affected and messed up by the inversion.
This could explain the high incidence of past still births, as if lots of genes are affected, and non-functional, the pregnancy would be rendered non-viable, or highly deleterious causing premature death.
b) There is a 50% chance of a child inheriting the defective copy of chromosome 1 (and 50% of a chance of them inheriting the normal chromosome 1. Therefore, there is likely a 50% chance that future offspring would be affected by defects
c) No. I would advise that the couple undergo preimplantation genetic diagnosis. In this, the couple undergoes in vitro fertilization (IVF). When embryos are produced through IVF, they can then be tested for the presence of the abnormal chromosome. Embryos will only be implanted into the mother if the normal chromosome 1 is present.
