A horse has 64 chromosomes and a donkey has 62 chromosomes. A cross between a fe
ID: 183861 • Letter: A
Question
A horse has 64 chromosomes and a donkey has 62 chromosomes. A cross between a female horse and a male donkey produces a mule, which is usually sterile. How many chromosomes does a mule have? Number 32 chromosomes Why are most mules are sterile? An even number of chromosomes are required for synapsis during prophase II and proper pairing during metaphase I. An even number of chromosomes are required for synapsis during prophase ll and proper pairing during metaphase II An even number of chromosomes are required for synapsis during prophase I and proper pairing during metaphase l. An even number of chromosomes are required for synapsis during prophase I and proper pairing during metaphase ll.Explanation / Answer
Hybrid sterility in mule occurs due to improper pairing of chromosomes.At prophase 1of meiosis, synapsis occurs at zygotene stage where tetrad is formed and genetic exchange takes place via crossing over at pachytene stage.Further equal number of chromosomes are separated apart in metaphase stage,which result into daughter cells with equal number of chromosomes.
But in case of mule,it is the result of two different species from horse and donkey.horse donate 32 chromosomes while donkey donate 31 chromosomes combining together to form 63 chromosomes in somatic cells of mule.But during sex cells formation,during meiosis,pairing at prophase 1 is improper and thus chromosomes are not separated at metaphase 1 stage.
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