Answer:
The correct answer is option B, that is, promoter, operator, gene.
Explanation:
In a prokaryote, just in front of the operator, the promoter is located, and just in front of the structural genes, the operator is located. All these in combination give rise to an operon.
Any gene, which codes for an enzyme or a structural protein is termed as a structural gene, in the lac operon, a structural gene codes for three distinct kinds of enzymes. A short sequence of DNA is situated just in front of the structural gene, which is known as the operator. An operator functions as a switch for transcription, that is, it monitors whether the process of transcription will take place or not.
Just in front of an operator, a sequence of a promoter is present, and for the transcription and translation of all the structural genes, the RNA polymerase needs to combine first with the promoter. In case, if no transcription is to take place, then the operator allows the repressor to bind with it and prevent the attachment of RNA polymerase with the promoter. Hence, the correct sequence of a prokaryotic operon is a promoter, operator, and gene.
Every cell of the organism has the same DNA sequence and same genes. However, not all genes are expressed in every single cell at the same time. Only those genes necessary for a specialised function of a specialised cell are expressed in the specialised cell. For example, skin cells have some different proteins than nerve cells. Genes responsible for those "skin proteins" are activated in skin cells and are turned off in nerve cells.
Answer:
Ss (male) × Ss (female)
Explanation:
This question involves a single gene coding for hair length in guinea pigs. Based on the information in this question, the allele for short hair (S) is dominant over the allele for long hair (s). This means that a guinea pig will only be phenotypically long-haired if the genotype is "ss".
According to this question, Two short-haired guinea pigs are mated several times. Out of the 100 offsprings produced by this cross, 25 of them have long hair (recessive). This means that the phenotypic ratio of this cross is 3 short hair : 1 long hair i.e. 100 - 25 = 75 short hair. 75/25 = 3/1 = 3:1
To produce this phenotypic ratio, the parents must both be heterozygous (Ss) for the hair length gene.
