Mrs Cortez has asked her students to write an explanation what chromosomes are and what they do. Four student examples are shown. Which student has written the best explanation of chromosomes?

A. Araceli
B. Becca
C. Charles
D. Daniel

The student that has written the best explanation of Chromosome is Araceli (A).

The student wrote that, 'chromosome in each cell contain many genes that hold hereditary information.'

Explanation:

Almost every body cell contains, within its nucleus, an identical copy of the entire complement of the individual's genetic material known as CHROMOSOME. Two important exceptions are red blood cells and the gametes or sex cells. Each chromosome is one of a pair, one inherited from the mother and one from the father, so the human cell had 46 chromosomes that can be arranged as 23 pairs.

Along the length of the chromosomes are the GENES which are composed of very long strands of DNA. DNA is a double- stranded molecule made up of two chains of nucleotides which consists of three subunits:

--> a sugar

--> a phosphate group

--> a base.

The main function of DNA which is found in the gene located in the chromosome is carrying huge amounts of information that determines all biological activities of an organism and which is transmitted from one generation to the next. Therefore the definition given by Araceli in the attached diagram is correct.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms