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ANSC 333 Exam 1 Questions & answers
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ANSC 333 Exam 1 Questions & answers
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ANSC 333 Exam 1If growth of the gubernaculum were blocked in a male bovine fetus, what would the
impact be on male fertility if this bull survived to adulthood? - ANS-Bull would be sterile.
Sterility results from a failure of testicular thermoregulation, testes must be kept a few
degrees below core body temperature for spermatogenesis to occur...testes found in the
abdomen would be too warm to sustain spermatogenesis.
Methods of sex determination vary across the animal kingdom. Identify the two general
mechanisms of sexual determination we discussed in class and provide a BRIEF and
general description of how each mechanism works. - ANS-Genetic sex determination.
Here, sex is determined by the genes that the embryo possess. For instance, in
mammals, females have two X chromosomes, while males have an X and a Y
chromosome. The Y chromosome contains a gene known as SRY; SRY is the master
regulator that causes the embryo to form a testis.
Environmental sex determination. Here, all animals have the same chromosomal (or
genetic) contribution; there are no sex chromosomes, every embryo inherits the same
chromosomes and some environmental queue causes an individual to develop into a
male or female. In some reptiles, the temperature at which eggs are incubated can
dictate which sex develops.
How would fertility be impacted if a genetically male bovine embryo contained a
mutation that prevented c-kit from being produced? Assume this embryo could survive
to adulthood. As an adult, would this animal be fertile? Explain your reasoning as to why
this impact on fertility comes about. - ANS-Kit ligand is the ligand that binds to the c-kit
receptor; c-kit receptors is expressed on the cell surface of the primordial germ cells
(PGCs). The binding of kit ligand to c-kit is the stimulus that leads the PGCs from the
yolk sac to the indifferent gonad. A mutation in c-kit would interfere with the binding to
kit ligand, therefore PGCs would fail to migrate to the indifferent gonad; PGCs would not
be able to differentiate into sperm, therefore this animal would be sterile.
What would happen with regard to the development of the tubular reproductive tracts in
a genetically female embryo if the indifferent gonads were removed. -
ANS-Paramesonephric duct system would develop into a female tubular reproductive
tract; mesonephric duct system would regress.
What would happen with regard to the development of the tubular reproductive tracts in
a genetically male embryo if the indifferent gonads were removed. -
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