1. You are studying a species of birds that does not have X and Y chromosomes, b
ID: 199709 • Letter: 1
Question
1. You are studying a species of birds that does not have X and Y chromosomes, but instead has Z and W sex chromosomes such that males are ZZ and females are ZW. 1A. Considering how sex determination is controlled differently by the X and Y chromosomes of Drosophila compared to humans, please suggest two possible ways that the Z and W chromosomes could control sex determination in these birds. 1B. To determine which of your two possible explanations for this sex determination is correct, you decide to examine the sex characteristics of individuals that have non-standard numbers of sex chromosomes- that is they have karyotypes that differ from the usual ZZ and ZW possibilities. Using the results from Drosophila and humans as a guide, please suggest which karyotypes you would consider most informative to determine how sex determination is controlled in birds. 2. You are studying a diploid species with a haploid n value of 8. A. How many total chromosomes would you expect this species to have during interphase of mitosis? B. How many total chromosomes are present at the metaphase plate of a mitotic cell. C. How many total chromatids are present at the metaphase II plate of a cell in meiosis. D. How many total chromatids are present at the metaphase I plate of a cell in meiosis. E. How many total chromatids are present during the Leptotene phase? F. What is the n value of a cell in prophase J during meiosis? G. What is the n value of a cell in prophase II during meiosis? H. What is the n value of a cell in prophase I of mitosis? 3. What are the names of the connection points on chromatids that microtubules attach to? What structures are the other ends of the microtubules associated with?Explanation / Answer
Question 1 B.
Answer. Although it is given that the karyotpe differ from usual ZZ and ZW possibilties. Still the sex of the individaul is going to be determined by presence or absence of W chromosome, therefore human Karyotype would be more informative as compared to the drosophila sex determination karyotype( Ratio of Autosome to sets of dex chromosome). Sex determination in bidrs is similar to sex determination in Humans and the only notable difference is that in birds sex is determined by heterogametic female( ZW) and in humans sex is determined by heterogametic male (XY).
Question 2.
Question (A)
Answer. Interphase is divided into further 3 phases each having different number of chromosomes,
G1 phase = 16
S-phase = 16 to 32 ( in the beginnong of S-phase no of chromosomes are 16 and at the end it is 32).
G2 phase = 32
Question (B)
Answer. 32
Question (C)
Answer. 32
Question (D)
Answer. 16
Question (E)
Answer. 32
Question (F)
Answer. 32 [ Although 'n' is used to denote haploid set of chromosomes which is constsnt for a species like here also it is given 8 in the first statement itself but here it looks like you are asking for number of chromosomes which are present at prophase-I stage of meiosis]
Question (G)
Answer. 16
Question(H)
Answer. 32
Question 3.
Answer.
One end of Microtubules is attach to the centromere of chromatids. Other end of microtubule is attached to "Centriole".
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