Question

Choose the correct combination.

a	Walter Sutton	$1$	Discovered penicillin
b	Thomas Hunt Morgan	$2$	Discovered chromosomal basis of heredity
c	James Watson	$3$	Described the phenomenon of linkage and crossing over
d	Alexander Fleming	$4$	Discovered double helical structure of DNA

• A. a-$1$, b-$4$, c-$2$, d-$3$
• B. a-$2$, b-$3$, c-$1$, d-$4$
• C. a-$3$, b-$2$, c-$1$, d-$4$
• D. a-$2$, b-$3$, c-$4$, d-$1$
• E. a-$4$, b-$1$, c-$2$, d-$3$

Answer 1

The correct option is D a-$2$, b-$3$, c-$4$, d-$1$

• Sutton deduced that chromosomes are the basis of heredity and that the reduction of chromosomes in meiosis is directly related to Mendel's laws of inheritance.
• Thomas Hunt Morgan described the phenomenon of linkage and crossing over. Morgan imagined that genes on chromosomes were similar to pearls on a string, in other words, they were physical objects. The closer two genes were to one another on a chromosome, the greater their chance of being inherited together. In contrast, genes located farther away from one another on the same chromosome were more likely to be separated during recombination. Therefore, Morgan correctly proposed that the strength of linkage between two genes depends upon the distance between the genes on the chromosome. This proposition became the basis for construction of the earliest maps of the human genome.
• James Dewey Watson discovered the structure of DNA in 1953 with Francis Crick.
• Scottish bacteriologist Alexander Fleming accidentally discovered the antibiotic in 1928, when he came back from a vacation and found that a green mold called Penicillium notatum had contaminated Petri dishes in his lab and were killing some of the bacteria he’d been growing.

So, the correct answer is 'a-2, b-3, c-4, d-1'.