【单选题】Certain dominant alleles are so important for normal development that mutant recessive alleles, called lethal alleles, lead to the death of the homozygous recessive organism. In many cases, the hetero...
【单选题】关于维修电工的安全规程,以下做法不正确的是().
A.
工作前,必须检查工具,测量仪表和防护用具是否完好
B.
任何电器设备未经验电,一律视为有电,不准用手触及
C.
电气设备及其带动的机械部分需要修理时,不准在运转中拆卸修理
D.
在配电总盘及母线上进行工作时,在验明无电后即可进行工作
【单选题】The alleles of a particular autosomal gene follow a simple dominance relationship. For which of the following individuals would the genotype be uncertain even if you knew the phenotype?
A.
a male with the dominant phenotype
B.
a female with the recessive phenotype
C.
a male with the recessive phenotype
【单选题】DNA双螺旋的每一螺距(以B-DNA为例)为
【单选题】DNA双螺旋的每一螺距(以B-DNA为例)为
【单选题】According to Mendel's laws, in a cross involving an individual that is homozygous dominant or a trait and an individual that is homozygous recessive for the same trait,( )
A.
the recessive trait will be present in a 1: 3 ratio in the F1 phenotypes
B.
the recessive trait will not be present in the F1 phenotypes
C.
the recessive trait will be present in the F1 phenotypes more often than the dominant trait
D.
the recessive trait will be present three times more often than the dominant trait in the F1 phenotype