1. You are studying a species of birds that does not have X and Y chromosomes, b
ID: 199492 • 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. 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 melosis. 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 I 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
Sex determination in birds:
Unlike fruit flies to human birds have ZW chromosomes as sex chromosomes. Male is homomorphic sex having ZZ, female is heteromorphic having ZW. Z chromosome is the large chromosome having majority of the sex linked genes. W is smaller micro chromosome.
In mammals male is heterogametic – XY
In birds male is homogametic – ZZ
Unlike in mammals where Y chromosome decides the sex, in birds W in ovum decides the sex.
One theory states that ZW system of sex determination is due strenuous male competition system in animals.
DMRT1 gene:
FOXL2, WNT4, RSPO1:
Question 2:
You are studying diploid species with a haploid n value of 8.
Mitosis is the cell multiplication occurs in somatic cells, meiosis is reduction division occurs in reproductive cells.
A. How many total chromosomes would you expect this species to have during interphase of mitosis.
Since it is a diploid species, during interphase of mitosis cell division total number of chromosome would be 16.
B. During metaphase of mitotic cell total of 16 chromosome will be present lined up in the center of the cell.
C. Total number of chromatids present at the metaphase II is 8 chromosomes and 16 chromatids.
D. Total number of chromatids present at the metaphase I is 16 chromosomes and 32chromatids.
E. During leptotene phase it has 16 chromosomes and 32 chromatids
F. During Prophase I of meiosis n value is 16.
G. During prophase II of meiosis n value is 8.
H. During prophase of mitosis n value is 16.
Question 3:
The two sister chromatids are attached at the center by a centromere.
These centromere has kinetochore protein to which the microtubule get attach, microtubules to the other end is attached to the spindle fibre.
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