Giardia intestinalis can cause disease in several different mammalian species, including humans. Giardia organisms (G. intestinalis) that infect humans are similar morphologically to those that infect other mammals, thus they have been considered a single species. However, G. intestinalis has been divided into different subgroups based on their host and a few other characteristics. In 1999, a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species. The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G. intestinalis and a few other morphologically distinct species of Giardia. The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species

Which of the following changes would a modern systematist be most likely to make after learning of the results of the rRNA analyses?

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#Question id: 12485

#Unit 2. Cellular Organization

Following statements are regarding to the centrosome cycle of an animal cell.

A. During G1, the daughter procentrioles continue to elongate.

B. During S phase, daughter procentrioles form adjacent to maternal centrioles so that two pairs of centrioles become visible within the centrosome. 

C. During G2 phase, the centrosome contains a single pair of centrioles.

D. At the beginning of mitosis, the centrosome splits, with each pair of centrioles becoming part of its own centrosome. As they separate, the centrosomes organize the microtubule fibres that make up the mitotic spindle.

Which of the following option is correct? 

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#Question id: 12486

#Unit 2. Cellular Organization

Which of the following process occur in prometaphase?

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#Question id: 12487

#Unit 8. Inheritance Biology

Neurofibromatosis type 1 is one of the most common autosomal dominant disorders. A woman with neurofibromatosis type 1 has an unaffected partner. Which of the following is correct regarding their children?

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#Question id: 12488

#Unit 8. Inheritance Biology

Retinoblastoma usually occurs as a sporadic event but in around 10% of cases there is a positive family history due to autosomal dominant inheritance. In these families the penetrance is approximately 80% (= 0.8). A woman with retinoblastoma, whose father and grandfather were also affected, has an unaffected partner with no relevant family history. Which of the following is correct regarding their children?

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#Question id: 12489

#Unit 8. Inheritance Biology

Achondroplasia shows autosomal dominant inheritance with complete penetrance. A man with achondroplasia has an unaffected partner of normal height. Their first two children are not affected. Which of the following is correct?

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#Question id: 12490

#Unit 8. Inheritance Biology

Tay-Sachs disease shows autosomal recessive inheritance. Parents of a newly diagnosed affected child are referred for genetic counselling. It would be correct to tell them that: