DNA STRUCTURE AND REPLICATION: (chapter 9)

What are the names of the four nitrogen bases?

A is for adenine and it forms together with T G is for guanine and it forms together with C C is for cytosine T is for thymine Their job is composing a code for DNA to shape the physical characteristics of most living things.

What is "backbone" of DNA?

The DNA backbone is a polymer with an alternating sugar-phosphate sequence. The deoxyribose sugars are joined at both the 3'-hydroxyl and 5'-hydroxyl groups to phosphate groups in ester links, also known as "phosphodiester" bonds

What is the end result of DNA replication? How many DNA molecules? Identical or different?

Two molecules of DNA instead of the original one; each molecule now contains one strand from the double helix of the original molecule, and one new strand

Which are pyrimidines?

Uracil = 2,4-dioxy pyrimidine Thymine = 2,4-dioxy-5-methyl pyrimidine Cytosine = 2-oxy-4-amino pyrimidine Orotic acid = 2,4-dioxy-6-carboxy pyrimidine

Be able to figure out the complement of a given DNA sequence.

For DNA, adenine (A) bases complement thymine (T) bases and vice versa; guanine (G) bases complement cytosine (C) bases and vice versa. With RNA, it is the same except that uracil is present in place of thymine, and therefore adenine (A) bases complement uracil (U) bases.

Which are purines and which are pyrimidines?

There are two kinds of nitrogen-containing bases - purines and pyrimidines. Purines consist of a six-membered and a five-membered nitrogen-containing ring, fused together. Pyridmidines have only a six-membered nitrogen-containing ring.

What are the basic steps in the replication of DNA?

1. DNA unzips 2. Nitrogen bonds floating outside of the nucleus attach with the unzipped DNA. 3. Two DNA strands with the exact same bases are formed

What is a mutation?

A mutation is a permanent change in the DNA sequence of a gene. Mutations in a gene's DNA sequence can alter the amino acid sequence of the protein encoded by the gene. Changes in the nucleotide sequence of DNA that are passed on from one cell, or organism, to another.

What three molecular structures makeup a single nucleotide?

A single nucleotide contains a nitrogenous base , a deoxyribose sugar molecule , and a phosphate group attached to the 5' side of the sugar . At the most basic level, all DNA is composed of a series of smaller molecules called nucleotides. In turn, each nucleotide is itself made up of three primary components: a nitrogen-containing region known as a nitrogenous base, a carbon-based sugar molecule called deoxyribose, and a phosphorus-containing region known as a phosphate group attached to the sugar molecule

Which are purines ?

Adenine = 6-amino purine Guanine = 2-amino-6-oxy purine Hypoxanthine = 6-oxy purine Xanthine = 2,6-dioxy purine

What components are in the center of the DNA molecule? (Phosphate groups, deoxyribose or nitrogen bases?)

DNA had two sides, or strands, and that these strands were twisted together like a twisted ladder -- the double helix. The sides of the ladder comprise the sugar-phosphate portions of adjacent nucleotides bonded together. The phosphate of one nucleotide is covalently bound (a bond in which one or more pairs of electrons are shared by two atoms) to the sugar of the next nucleotide. The hydrogen bonds between phosphates cause the DNA strand to twist.

When in the cell cycle is DNA replicated?

DNA replication occurs during the S stage of interphase. Interphase is the stage between two mitotic or meiotic divisions. It can be slpit into three stages:G1, S and G2. During G1 (gap 1), cells grow and build up ATP on preparation for DNA replication. During the S (synthesis) phase the DNA is replicated. During the G2 phase the cell prepares itself for the process of cell division (mitosis or meiosis).

The two DNA strands are attached to each other because what molecules are attracted to each other?

Each base pair is formed from two complementary nucleotides (purine with pyrimidine) bound together by hydrogen bonds. The two strands of DNA are held together by weak hydrogen bonds.

Why is DNA referred to as the "double helix"?

Its structure is two spirals interlaced; double meaning two, helix being the technical word for such a shape. Double Helix refer to DNA and the coil configuration of two complementary, antiparallel strands. DNA is a normally double stranded macromolecule. Two polynucleotide chains, held together by weak thermodynamic forces, form a DNA molecule.

Are the nitrogen bases in one strand attached to the phosphate group or the deoxyribose?

The deoxyribose . The deoxyribose and the phosphate groups form the backbone of the nucleic acid molecule. Nitrogenous bases, which are bound to the deoxyribose groups, protrude from the backbone. In the double helix, these bases protrude into the centre of the double helix. So, the answer is, the deoxyribose.

What components are in the center of the DNA molecule? (Phosphate groups, deoxyribose or nitrogen bases?) Cont...

The nitrogenous bases point inward on the ladder and form pairs with bases on the other side, like rungs. Each base pair is formed from two complementary nucleotides (purine with pyrimidine) bound together by hydrogen bonds. The base pairs in DNA are adenine with thymine and cytosine with guanine

The two DNA strands are attached to each other because what molecules are attracted to each other? Cont...

The nucleotides connect the two strands through hydrogen bonds. Because each nucleotide has a unique complimentary nucleotide, each strand contains all the information required to synthesize a new DNA molecule. The double stranded structure also makes the molecule more stable.

When in the cell cycle is DNA replicated? Why?

The replication of DNA forms new DNA which form new cells when put in the cells of new nucleus's. The body continuously needs to produce new cells through mitosis for growth and repair and therefore without DNA replication these new cells would not be able to be made, which are needed in the human body.

What type of bonds hold together the complementary nitrogen bases? Are these bonds strong or weak? To which base is adenine attracted? To which base is guanine attracted?

This is how the two strands of DNA link together. There are four types of base. Thyamine and cytosine are pyrimidines and guanime and adenine are purines (pyrimidine and purine relates to the shape of the molecule). As the name suggests the base will only pair with another base that is complementary in shape. Thyamine pairs with adenine and cytosine pairs with guanime.The pairs of nitrogenous bases are held together by bonds caused by hydrogen that are called hydrogen bonds. Adenine and thyamine have two hydrogen bonds pairing them together wheras cytosine and guanine have 3.

What is the "backbone" of DNA composed of?

Phosphate molecules and deoxyribose sugar. DNA backbones are made up of deoxyribose, a pentose sugar. These sugars are connected via a phosphodiester bond. The phosphate groups have a negative charge to them, which allows positively charged histone proteins to interact with them in forming chromatin. Also helps separate DNA with gel electrophoresis.

Know the 3 enzymes involved and what they do.

Primase - Forms an RNA primer Polymerase - Adds nucleotides to the new Okazaki fragment only at the 3' end, continuing until it encounters the primer on the previous Okazaki fragment. Ligase - Catalyzes the formation of the phosphodiester linkage that finally joins the two Okazaki fragments.

Which are composed of 1 ring and which are composed of 2 rings?

Purine - A pyrimidine ring fused to a imidazole ring. Contains two carbon-nitrogen rings and four nitrogen atoms. Pyramidine - Contains one carbon-nitrogen ring and two nitrogen atoms.

How do we refer to DNA replication?

The process of making an identical copy of a section of duplex (double-stranded) DNA, using existing DNA as a template for the synthesis of new DNA strands. In humans and other eukaryotes, replication occurs in the cell nucleus.