Question

when the chromosomes in a cell are spread out and examined under a microscope, they clearly differ in size and shape. this observation led researchers to conclude that there are different types of chromosomes. to distinguish them, chromosomes are numbered. human cells, for example, have 23 different types of chromosomes. they are numbered 1 - 22; the 23rd type is a sex chromosome called x or y. (more on sex chromosomes later.)
the key thing to understand about chromosomes is that different types contain different and unique genes. human chromosome 1, for example, contains about 2000 genes, including one whose product influences cell division rates as the brain is developing. chromosome 2 has about 2700 genes, including one that codes for a protein involved in moving vesicles around cells. and so on.
life scientists use some key terms to describe the collection of chromosomes that are found in a cell.

1. haploid number refers to the number of different types of chromosomes found in each cell an organism, and is symbolized with an n. in humans, n = 23.
2. many or most eukaryotes have two or more of each type of chromosome. ploidy refers to the number of copies of each type of chromosome present. ploidy is symbolized with a number before the n that refers to haploid number. human cells have two of each type of chromosome, so each cell has a total of 46 chromosomes present. humans are said to be diploid — the greek root di means two or double — and 2n = 46. cells that only have one of each type of chromosome are said to be haploid.

the commercial strawberries you grow in your garden or buy in a store have seven different types of chromosomes and eight of each type. which of the following statements about strawberries are correct? select all that apply.
□ strawberries are said to be hexaploid, because the greek root hexa means six.
□ strawberries are 8n.
□ in strawberries, n = 7.
□ strawberries have a total of 64 chromosomes in each cell.

Explanation:

• For the statement "Strawberries are said to be hexaploid, because the Greek root hexa means six":
• Hexa means six, but strawberries have eight copies of each chromosome type (octoploid, not hexaploid). So this statement is incorrect.
• For the statement "Strawberries are \(8n\)":
• Given that there are eight copies of each chromosome type and \(n\) is the haploid number (number of different chromosome types). So if there are seven different chromosome types (\(n = 7\)), and eight copies of each, the ploidy is \(8n\). This statement is correct.
• For the statement "In strawberries, \(n=7\)":
• Since there are seven different types of chromosomes, by the definition of \(n\) (haploid number as the number of different chromosome types), \(n = 7\). This statement is correct.
• For the statement "Strawberries have a total of 64 chromosomes in each cell":
• If \(n = 7\) and ploidy is \(8n\), then the total number of chromosomes is \(8\times7=56

eq64\). So this statement is incorrect.

Answer:

• B. Strawberries are \(8n\)
• C. In strawberries, \(n = 7\)