In chickens, a key gene involved in sex determination has recently been identified. Called DMRT1, it is located on the Z chromosome and is absent on the W chromosome. Like SRY in humans, it is male determining. Unlike SRY in humans, however, female chickens (ZW) have a single copy while males (ZZ) have two copies of the gene. Nevertheless, it is transcribed only in the developing testis. Working in the laboratory of Andrew Sinclair (a co-discoverer of the human SRY gene), Craig Smith and colleagues were able to 'knock down' expression of DMRT1 in ZZ embryos using RNA interference techniques. In such cases, the developing gonads look more like ovaries than testes. What conclusions can you draw about the role that the DMRT1 gene plays in chickens in contrast to the role the SRY gene plays in humans?
3. Extensions to Mendelian Inheritance
Sex Chromosome
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
How many chromosomes are present in a typical human somatic cell?
A
23
B
44
C
48
D
46
Verified step by step guidance1
Understand that human somatic cells are all the body cells except the gametes (sperm and egg cells).
Recall that humans have 23 pairs of chromosomes, where each pair consists of one chromosome from the mother and one from the father.
Calculate the total number of chromosomes in a somatic cell by multiplying the number of pairs by 2, since each pair has two chromosomes.
Express this calculation as an equation: $\text{Total chromosomes} = 23 \times 2$.
Recognize that the result represents the diploid number of chromosomes in a typical human somatic cell.
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