The process during which one type of bacteria is permanently transformed into another is known as transformation.

b. transformation

Bacteriophages are viruses that invade bacteria. They have a protein coat and a core made of deoxyribonucleic acid.

d. viruses

Hershey and Chase wanted to find out which part of the bacteriophage will enter the bacteria and pass on genetic material – protein or DNA. The proteins were marked with radioactive sulfur-35, while DNA contained radioactive phosphorus-32. At the end of this experiment, they found phosphorus-32 in the bacteria, which supports Avery’s theory that genes are located in the DNA of the cell.

c. Alfred Hershey and Martha Chase

The experiments of Griffin and Avery proved that DNA was the transforming factor that carries traits and can be passed on the next generation. Three roles of the DNA molecule in heritage are in storage, copying and transmitting genes. Every cell contains DNA, where is the complete genetic material stored. It must be doubled during the cell division and then passed on the daughter cells.

b. carry and make copies of information

Griffin experimented with heat-killed S and R strain bacteria. He discovered that their offspring had the ability to develop pneumonia in mouses, even though none of the parental bacteria could cause that disease. He concluded that heat-killed S strain bacteria passed on their genetic material to the offspring, so the harmless bacteria transformed into the type that causes pneumonia. He named the process transformation and concluded that gene was a transforming factor.

Hershey and Chase wanted to find out which part of the bacteriophage will enter the bacteria and pass on genetic material – protein or DNA. The proteins were marked with radioactive sulfur-35, while DNA contained radioactive phosphorus-32. At the end of this experiment, they found phosphorus-32 in the bacteria, which supported theory that genes are located in the DNA of the cell.

Nucleotides consist of deoxyribose, the phosphate group, and a nitrogenous base (adenine, cytosine, thymine, and guanine).

b. an amino acid

Erwin Chargaff first noticed that the percentage of adenine and thymine, as well as guanine and cytosine, is almost the same in every DNA molecule. That is known as the Chargaff’s rule.

a. [A] = [T], and [G] = [C]

In DNA, the strands are antiparallel, they are composed of nucleotides that are connected with covalent bonds. Two strands are connected with weak, hydrogen bonds. That is an important characteristic which facilitates cell division, regarding the duplication of DNA molecule.

c. weak hydrogen bonds between nitrogenous bases.

Nucleotides consist of deoxyribose, the phosphate group, and a nitrogenous base (adenine, cytosine, thymine, and guanine).

Watson and Crick made the first model of the DNA. The strands of the DNA molecule are antiparallel, they are composed of nucleotides that are connected with covalent bonds. Two strands are connected with weak, hydrogen bonds. According to the Chargaff’s rule, adenine binds with thymine, while guanine binds with cytosine in every DNA molecule.

The antiparallel arrangement of strands allows them to follow the Chargaff’s rule. In this way, nucleotides of one strand are oriented in the center of the molecule where they bind with adequate nucleotides of the other DNA strand.

The first picture of this molecule was made by Rosalind Franklin. She isolated DNA molecules, which was then stretched until most of them were parallel. She successfully made an X-ray image, in which the DNA had a shape of an X. This led to the conclusion that the DNA molecule has the shape of a helix.

DNA molecule in prokaryotes is usually single and circular. It is located in their cytoplasm.

c. cytoplasm

DNA molecule in eukaryotic cells is located in the nucleus.

a. nucleus

DNA polymerase is an enzyme that attaches matching nucleotides to the DNA strand in a process of replication.

d. DNA polymerase

Base pairing follows the Chargaff’s rule. According to this rule, adenine binds only with thymine, while cytosine binds only with guanine. During replication, DNA polymerase attaches matching nucleotides to the DNA strand. Practically, if the sequence on the DNA strand of the parental cell is GATCG, the base sequence that is made by DNA polymerase will be CTAGC.

A prokaryotic cell has a single and circular DNA molecule that consists of two strands. This genetic material is found in the region of cytoplasm, known as a nucleoid. A nucleoid doesn’t have a membrane that separates it from the rest of the cytoplasm, oppose the nucleus in eukaryotic cells. Some prokaryotic cells contain DNA outside of nucleoid. These structures are called plasmids.

Replication process begins in the S phase, in one or more spots on the DNA molecule, where the replication fork is being formed. From this point, DNA polymerase attaches matching nucleotides to the DNA strand. Base pairing follows the Chargaff’s rule. According to this rule, adenine binds only with thymine, while cytosine binds only with guanine. Practically, if the sequence on the DNA strand of the parental cell is GATCG, the base sequence that is made by DNA polymerase will be CTAGC. Replication is always done in two directions (always from 5′ to 3′), simultaneously on both of the DNA strands of the parental cell. In this way, both of the daughter cells have the same DNA as the parental cell.

Griffin experimented with heat-killed S and R strain bacteria. He discovered that their offspring had the ability to develop pneumonia in mouses, even though none of the parental bacteria could cause that disease. He concluded that heat-killed S strain bacteria passed on their genetic material to the offspring, so the harmless bacteria transformed into the type that causes pneumonia. He named the process transformation and concluded that gene was a transforming factor.

Avery’s team proved in 1944 that DNA contains genetic material. They concluded that DNA of the heat-killed S strain, when mixed with R strain bacteria, was passed on the next generation, which was able to induce pneumonia. They have made an experiment where they have been previously resolved different types of molecules of the heat-killed S strain bacteria. The transformation process occurred even though lipids, proteins, carbohydrates, and RNA were previously dissolved. However, if the DNA of the heat-killed S bacteria was resolved and these bacteria were mixed with R strain bacteria, the transformation didn’t occur. They concluded that DNA is the transforming factor.

Watson and Crick made the first model of the DNA. The strands of the DNA molecule are antiparallel, they are composed of nucleotides that are connected with covalent bonds. Two strands are connected with weak, hydrogen bonds. This model showed base pairing, which follows Chargaff’s rule. According to this rule, adenine binds only with thymine, while guanine binds only with cytosine in every DNA molecule. It explained that the percentage of adenine and thymine, as well as guanine and cytosine, is almost the same in every DNA molecule.

The distance between two strands of the DNA is the same through its whole length, which was proven with an X-ray image of the molecule made by Rosalind Franklin. Based on this discovery, Watson and Crick concluded that in base pairing, a purine always binds with a pyrimidine base with two or three hydrogen bonds. Purine bases are adenine and guanine and they are larger than pyrimidine bases – cytosine and thymine. Since the percent of adenine is nearly the same as thymine, as well as the percent of guanine is almost equal to cytosine, they have made a DNA model in which complementary bases are adenine-thymine and guanine-cytosine.

During replication, one original DNA splits into two strands that serve as models for building two new molecules that are exactly the same as was the original. During photocopying a paper, we also end up with two identical papers, but one of them is the original, while the other is a brand new paper.

The replication of a DNA molecule is done in the S phase of the cell cycle. Before mitosis begins, a parental cell must double its genetic material so each chromosome can organize into two chromatids, which can separate during mitotic division. In this way, one diploid parental cell gives two diploid daughter cells.

Watson and Crick presented a model of DNA molecule that has two antiparallel strands which consist of nucleotides connected with covalent bonds. Two strands are connected with weak, hydrogen bonds. That is an important characteristic which facilitates DNA replication because they are easy to break. Watson and Crick also concluded that complementary bases are adenine-thymine and guanine-cytosine. In this way, each strand of the DNA molecule serves as a model for building two new molecules that are exactly the same as was the original.

Ultraviolet light is considered a mutagen because it makes chemical changes in the DNA molecule. Prolonged and frequent exposure to ultraviolet light can cause dimerizing and oxidative mutations on the molecule of DNA. Cyclobutane pyrimidine dimer is the most common of dimerizing mutations. In this case, a double covalent bond is made between two adjacent pyrimidines, which disables them to bind with their complementary bases on the other strand. Oxidative mutations imply forming of oxidized bases which don’t pair with their complementary bases. These processes induce DNA repairing, that is usually made by cutting off these changed parts. DNA polymerase is activated in adding nucleotides in order to repair these areas. However, mistakes could also be made in this process, causing new mutations of the DNA molecule. Because the penetration of UV light is low, only DNA molecules in our skin cells are affected. A very high percentage of skin cancers is directly related with patients overexposure to the ultraviolet light.

The first picture of a DNA molecule was made by Rosalind Franklin. In this picture, we can see that the DNA molecule has the shape of a helix with two strands, where the distance between them is the same through its whole length, and the nitrogenous bases are near the center of the DNA molecule. The question that needed an answer was how the bases are paired. Watson and Crick concluded that in base pairing, a purine always binds with a pyrimidine base with two or three hydrogen bonds. Purine bases are adenine and guanine and they are larger than pyrimidine bases – cytosine and thymine. Since the percent of adenine is nearly the same as thymine, as well as the percent of guanine is almost equal to cytosine, they have made a DNA model in which complementary bases are adenine-thymine and guanine-cytosine.

Gene mapping gives us an approximate gene position on a certain chromosome, as well as the distance between these genes. However, DNA sequence shows nucleotides and their exact order in different genes.

DNA molecule has two strands that contain nucleotides in a unique order which determines complete genome. In this way, information about genes is stored. Two antiparallel strands are interconnected with weak, easy to break, hydrogen bonds, which facilitates the replication process. Since these strands are antiparallel and bases are complementary (A-T and G-C), each strand of the DNA molecule serves as a model for building two new molecules that are exactly the same as was the original. In this way, information is transmitted to two daughter cells.

Erwin Chargaff first noticed that the percentage of adenine and thymine, as well as guanine and cytosine, is almost the same in every DNA molecule. That is known as the Chargaff’s rule. As a percentage of thymine in a human genome is 29,4, we can conclude that the percentage of adenine is also around 29%.

Erwin Chargaff first noticed that the percentage of adenine and thymine, as well as guanine and cytosine, is almost the same in every DNA molecule. That is known as the Chargaff’s rule. The percentage of adenine in a bacterial genome is 13,4, which is the same as the percentage of thymine.
A = 13,4 T = 13,4

A + T + G + C = 100
13,4 + 13,4 + G + C = 100
G + C = 100 – 13,4 – 13,4
G + C = 73,2
G = C
Therefore, we can conclude that percentage of guanine and cytosine in the bacterial DNA is around 36,6 (73,2/2).

Erwin Chargaff first noticed that the percentage of adenine and thymine, as well as guanine and cytosine, is almost the same in every DNA molecule. That is known as the Chargaff’s rule. However, this rule will not apply to one, isolated strand. For example, if a part of a DNA has sequence 5′ – AATTGTC – 3′ on one strand, the corresponding sequence of the other strand will be 3′ – TTAACAG – 5′. On both strands, A = T and G = C, but on either one of these strands, we can not use the Chargaff’s rule.

D. The four nitrogenous bases may have any value

A gene represents a sequence of nucleotides in a DNA molecule that contains information about coding a functional protein. Three roles of the DNA molecule in heritage are in storage, copying and transmitting genes.
Deoxyribonucleic acid is made of nucleotides which are combined with covalent bonds and form a chain. Nucleotides consist of deoxyribose, the phosphate group, and a nitrogenous base (adenine, cytosine, thymine, and guanine). A DNA molecule has two antiparallel strands that are interconnected with weak, hydrogen bonds, which facilitates the replication process. Pyrimidine base on one strand is always paired with the corresponding purine base on the other strand. Adenine binds only with thymine, while cytosine binds only with guanine. This allows DNA molecule of a parental cell to divide into two strands, in order to double genetic material before a mitotic division. DNA molecules are organized in chromosomes, which makes a karyotype of an individual.

Hershey and Chase wanted to find out which part of the bacteriophage will enter the bacteria and pass on genetic material – protein or DNA. The proteins were marked with radioactive sulfur-35, while DNA contained radioactive phosphorus-32. Their experiment consisted of the following steps:

1. Bacteriophages are grown with radioactive sulfur-35 and radioactive phosphorus-32
2. Bacteriophages and bacteria are mixed for several minutes
3. Bacteriophages and bacteria are isolated
4. Bacteria are analyzed for radioactivity
5. Almost all the radioactivity originated from radioactive phosphorus-32

At the end of this experiment, they found phosphorus-32 in the bacteria, which supports Avery’s theory that genes are located in the DNA of the cell.

DNA molecule in prokaryotes is usually single and circular, while eukaryotes have up to one thousand more genetic material in their nuclei. Replication process begins in one spot in prokaryotes, while a number of spots can be even several hundred in the DNA of eukaryotes. In both cases, replication is done in two directions. In eukaryotic cells, DNA molecule is wrapped around histones and forms nucleosomes. These structures slow down DNA polymerase, which moves about 50 times slower than in prokaryotes.

Watson and Crick made the first model of the DNA. Deoxyribonucleic acid is made of nucleotides which are combined with covalent bonds and form a chain. Nucleotides consist of deoxyribose, the phosphate group, and a nitrogenous base (adenine, cytosine, thymine, and guanine). The strands of the DNA molecule are antiparallel. Two strands are connected with weak, hydrogen bonds. According to the Chargaff’s rule, adenine binds with thymine of the other strand, while guanine only binds with cytosine of the other strand in every DNA molecule. When we see the animated 3D model of the DNA molecule, everything that we read about its chemical structure in the textbook becomes perfectly clear.