B. meiosis. This process randomly rearranges the pairs of homologous chromosomes in formation of the sex cells. In addition, there is crossing-over of the chromatids while the homologous chromosomes are synapsed during meiosis I.
Answer:brain
Spinal cord
Explanation: the two make up the nervous system
Answer:
the first question answer is C and for the second one is D
Answer:
A) histone coding genes
Explanation:
Histones are the proteins involved in the packing of DNA in eukaryotes. They are positively charged proteins and are not found in bacteria. To analyze the evolutionary relationship in a gene between eukaryotes and bacteria, one must choose the gene present in both of them. The tRNA, rRNA and hexokinase encoding genes are common to both bacteria and eukaryotes. Therefore, one of these genes may be chosen for the study. However, histone encoding genes are not present in the genomes of bacteria. Therefore, the study of the histone encoding gene would not be useful for the mentioned purpose.
Answer:
a. + glucose, + lactose = On
b. - glucose, - lactose = Off
c. + glucose, - lactose = Off
d. - glucose, + lactose = On
Explanation:
Lac operon has both types of control, repressible and inducible.
Whenever glucose level is low in the cell, an enzyme known as adenylyl cyclase raises the level of cAMP which forms a dimer with CRP protein and they both act as activator of lac operon and cause expression.
Apart from this, when lactose is present in the cell, β-galactosidase enzyme metabolizes lactose to form allolactose which causes allosteric repulsion in the lac repressor and causes its removal from the operator. As soon as repressor is removed lac operon gets activated.
In wild type lac operons, the expression of lac operon occurs when glucose level is low in the cell and lactose is present but in this mutant presence or absence of glucose will not make a difference because CRP will bind Plac promoter independent of cAMP level i.e. activator CRP will work even in high glucose concentration. If lactose is present then lac operon will always express so in option 'a & d' lac operon will express but in option 'b & c' it will not express.
