Answer: Each chromosome actually consists of two sister chromatids, which are joined together at a centromere. ... During this process, sister chromatids separate from each other and move to opposite poles of the cell. This happens in four phases, called prophase, metaphase, anaphase, and telophase. Homologous chromosomes are two pieces of DNA within a diploid organism which carry the same genes, one from each parental source. In simpler terms, both of your parents provide a complete genome. Each parent provides the same 23 chromosomes, which encode the same genes. Sister chromatids are two identical copies of the same chromosome formed by DNA replication, attached to each other by a structure called the centromere. During cell division, they are separated from each other, and each daughter cell receives one copy of the chromosome. Spindle fibers are filaments that form the mitotic spindle in cell division, i.e. mitosis and meiosis. They are chiefly involved in moving and segregating the chromosomes during nuclear division. Spindle fibers are made up of microtubules. In meiosis. Each pair of chromosomes—called a tetrad, or a bivalent—consists of four chromatids. At this point, the homologous chromosomes exchange genetic material by the process of crossing over (see linkage group). The tetrad occurs during the first phase of meiosis. It is the foursome of chromatids that forms when replicated homologous chromosomes align. It must be formed for crossing over to occur. It is broken apart when the homologous chromosomes separate in meiosis I.
Explanation:
Answer:
<em>Both the parents are carriers of sickle cell anaemia.</em> A carrier can be described as a person who carries a diseased causing allele but the allele is not functional in the body of the person due to the dominant allele suppressing its activity. Such kind of people might produce children actually having the disease.
In the above scenario, <em>there is a 25% chance that the children born will be normal. </em>
<em>There is a 50 percent chance that the children born will be carriers, like the parents.</em>
<em>There is a 25% chance that the child born from these parents might have sickle cell anaemia.</em>
Answer:
Either A or C but A is a bit more true
Explanation:
You can measure one on option C but you can measure both
on answer A. Hope this helps you out.
<span>
Wind dispersion of reproductive cells allowed in seedplants to colonize
land away from water supplies. If water is needed to
passively transport gametes to each other and protect them from desiccation
plants were limited to densely inhabited space near water sources.
Bryophytes & ferns (seedless) are dependent on moist environments
for reproduction but the first seed plants developed an alternate
delivery system allowing independence from water- assisted reproduction.
Conifers produce pollen that can survive by carrying water and
nutrients along. Wind can now carry these male gametophytes to female
gametophytes under the scales of a cone. Fertilization produced a
diploid seed. The seed is protected and can survive dry conditions for a
period of time before growing. Pollen and seeds transferred a conifer’s
water dependence for their reproduction to wind dependence. </span>
