Question 1

The division of a bacterial cell occurs as the:

Accepted Answer

The new membrane and cell wall materials grow and form a septum, dividing the cell into two daughter cells. This process is known as binary fission. Chromosomes are replicated and pulled apart, but this is not the direct cause of the cell division. Actin and microtubules are not present in bacterial cells, so they cannot constrict the cytoplasm. The cell wall does not develop cracks around the equator of the cell.

Question 2

You are assembling a model of a chromosome,but begin having some trouble when you get to the step of forming chromatin loops.If you are unable to resolve this problem,what step of chromosome structure would you be unable to achieve?

Accepted Answer

Chromatin loops are crucial for the formation of higher-order chromosome structures, including rosettes. Without the ability to form chromatin loops, the assembly process cannot progress to the stage where these larger, more complex structures like rosettes are formed. Rosettes are a part of the hierarchical organization of chromatin in the nucleus, representing a level of structure beyond the solenoid or nucleosome level, involving the folding and organization of chromatin into larger, looped structures.

Question 3

Eukaryotic chromosomes are composed of a complex of 60% protein and 40% DNA.This complex is referred to as:

Accepted Answer

Eukaryotic chromosomes are composed of a complex of 60% protein and 40% DNA, which is referred to as chromatin. The histone complex refers to the proteins that make up the nucleosome structure within the chromatin, while cohesin is a protein complex that helps hold sister chromatids together during cell division. The kinetochore is a protein structure on chromosomes to which spindle fibers attach during cell division.

Question 4

If a cell contained a mutation in the gene that encodes FtsZ,which process would be affected?

Accepted Answer

FtsZ is a protein that is essential for cell division. It forms a ring-like structure at the site of cell division and helps to constrict the cell membrane, eventually leading to the separation of the two daughter cells. A mutation in the gene that encodes FtsZ would therefore affect the process of cytokinesis, which is the physical separation of the two daughter cells.

Question 5

If there are 32 sister chromatids in a normal somatic cell,what is the haploid number for that cell?

Accepted Answer

The haploid number, represented by "n", is the number of chromosomes in a gamete (sex cell). A somatic cell is a non-sex cell and has a diploid number of chromosomes (2n). In this case, since there are 32 sister chromatids, we can divide by 2 to determine the diploid number, which is 16 (2n=16). To find the haploid number, we divide the diploid number by 2, which gives us 8 (n=8). Therefore, the correct answer is choice A.

Question 6

Before cell division of somatic cells,each chromosome must be replicated.After replication,the resulting two parts of each chromosome are held together by cohesin at the centromere.These two parts are referred to as:

Accepted Answer

After replication, the two identical copies of a chromosome are referred to as sister chromatids. They are held together by a protein complex called cohesin at the centromere. Sister chromatids separate during cell division and go to different daughter cells. Homologous chromosomes, on the other hand, are pairs of chromosomes that carry genes for the same traits but may differ in the actual genetic information they carry. Daughter chromosomes and kinetochores are not correct terms for describing the replicated chromosomes held together by cohesin. Genes are specific sequences of DNA that code for proteins or RNA.

Question 7

If there are 32 sister chromatids in a normal somatic cell,how many chromosomes are there?

Accepted Answer

Sister chromatids are the replicated forms of a single chromosome. Therefore, if there are 32 sister chromatids, there are only 16 unique chromosomes in the somatic cell.

Question 8

How does the organization of the bacterial genome differ from the organization of the eukaryotic genome?

Accepted Answer

Most bacterial chromosomes are circular, whereas eukaryotic chromosomes contained in the nucleus are linear. Additionally, eukaryotic genomes are often made up of multiple chromosomes, while bacterial genomes typically have one circular chromosome.

Question 9

A person whose cells all contain a chromosome number of 2n+1 most likely has what type of condition?

Accepted Answer

A chromosome number of 2n+1 indicates that there is an extra chromosome present. This is commonly seen in trisomy conditions, such as Down syndrome, where an individual has three copies of chromosome 21 instead of the normal two copies. A person with monosomy would have a chromosome number of 2n-1, indicating that they are missing a chromosome. This is typically seen in conditions such as Turner syndrome, where females only have one X chromosome instead of the normal two.

Question 10

A cell biologist produces a karyotype of mouse somatic cells arrested in mitosis.She sees 40 chromosomes,which is completely normal for mice.Based on this information,what is the haploid number of chromosomes for mice?

Accepted Answer

The haploid number of chromosomes is half of the diploid number. Since the mouse somatic cells have 40 chromosomes, the diploid number is 2 times that, or 80 chromosomes. Therefore, the haploid number of chromosomes for mice is 40/2, which is 20.

Question 11

The accommodation of the very long DNA strands that are part of a chromosome into the limited space of the nucleus is achieved by coiling the DNA around beads of histones into repeating subunits.These DNA-wrapped histones are called:

Accepted Answer

The repeating subunits of DNA-wrapped histones are called nucleosomes. Solenoids, chromatin loops, and rosettes are not the correct terms for describing this structure.

Question 12

A somatic cell from a garden pea normally contains 14 chromosomes.How many sister chromatids would that cell contain during G1 of the cell cycle?

Accepted Answer

The answer of A somatic cell from a garden pea...

Question 13

In later chapters,you will learn more about the regulation of gene expression.One way to regulate gene expression is to make changes to the histone proteins to alter how tightly the DNA is coiled and wrapped.The more tightly coiled and wrapped a particular region of DNA is,the less likely it is that the genes in that region will be expressed.Bearing this in mind,how tightly do you think regions of heterochromatin are compacted?

Accepted Answer

Regions of heterochromatin are known to be heavily compacted due to the presence of highly condensed chromatin structures. This prevents access of transcription machinery to the genes that lie within the heterochromatin region, resulting in their suppression or silencing.

Question 14

The point of constriction on chromosomes that contains certain repeated DNA sequences that bind specific proteins is called:

Accepted Answer

The point of constriction on chromosomes that contains certain repeated DNA sequences that bind specific proteins is called the centromere.

Question 15

In bacterial cell division,the cell divides into two nearly equal halves.This process is referred to as:

Accepted Answer

Binary fission is the process by which bacterial cells divide into two nearly equal halves. Mitosis is a process that occurs in eukaryotic cells, not bacterial cells. Fusion is a process by which two cells combine to form one cell, also not applicable in bacterial cell division. Meiosis is a type of cell division that produces gametes, also not applicable in bacterial cells. Cytokinesis is the final stage of cell division in which the cytoplasm divides to form two separate cells, which applies to binary fission.

Question 16

The number of chromosomes in diploid eukaryotic cells

Accepted Answer

The number of chromosomes in diploid eukaryotic cells can vary considerably between different species, ranging from just 2 in some species of roundworms to over 1000 in some species of ferns. Therefore, option D is the only correct answer. Options A and B are incorrect as the number of chromosomes is not always 46 and cannot be predicted by the size of the organism. Option C is also incorrect as the number of chromosomes does not change with growth and aging, it remains constant throughout the life of an organism.

Question 17

These structures are held together by cohesin:

Accepted Answer

Cohesin holds sister chromatids together during cell division until they are separated during anaphase.

Question 18

The two copies of each type of chromosome found in normal somatic (body)cells in an organism,throughout the cell cycle,are called:

Accepted Answer

The two copies of each type of chromosome found in normal somatic cells are called homologous chromosomes. This is because they carry the same genes but may have different versions of those genes (alleles). Sister chromatids, on the other hand, are identical copies of a single chromosome that are produced during DNA replication. Daughter chromosomes are divided sister chromatids during cell division. Kinetochores are protein structures that form on the centromere of a chromosome and are important for spindle fiber attachment during cell division.

Question 19

A scientist wants to study histones.Histones are:

Accepted Answer

Histones are proteins that double-stranded DNA molecules wrap around in eukaryotes. This helps to form a structure known as chromatin, which can be further condensed into chromosomes during cell division. Histones play a key role in regulating gene expression and DNA replication.

Question 20

A somatic cell from a corn plant normally contains 20 chromosomes.How many sister chromatids would that cell contain during G2 of the cell cycle?

Accepted Answer

During G2 of the cell cycle, the DNA has already replicated to form sister chromatids. Therefore, each chromosome would have two sister chromatids, resulting in a total of 40 chromatids in a somatic cell with 20 chromosomes.

Quiz 10: How Cells Divide