DNA Intro: DNA

Background Information: It is important to recall from the information from unit C about DNA. The acronym DNA stands for Deoxyribonucleic Acid. It is important to recall from the information from unit C about DNA. The acronym DNA stands for Deoxyribonucleic Acid. DNA is the molecule that makes up Chromosomes and serves as hereditary information. DNA is the molecule that makes up Chromosomes and serves as hereditary information.

Nucleic Acids There are two types of nucleic acids, DNA and RNA. Both DNA and RNA are polymers of nucleotides. (ie chains of joined nucleotides). They form genetic material and are involved in the functioning of chromosomes and protein synthesis. There are two types of nucleic acids, DNA and RNA. Both DNA and RNA are polymers of nucleotides. (ie chains of joined nucleotides). They form genetic material and are involved in the functioning of chromosomes and protein synthesis. DNA Structure The shape is a double helix made up of repeating nucleotide units. The shape is a double helix made up of repeating nucleotide units.

Nucleotides are composed of 3 basic parts Nucleotides are composed of 3 basic parts i) Phosphoric acid (Phosphorus) ii) 5 carbon sugar (Deoxyribose)

iii) Nitrogen Base : a. Purines: (**larger base than Pyrimidines**) a. Purines: (**larger base than Pyrimidines**) (Double ring) (Double ring)

b. Pyrimidines: (Single ring)

When the bases bond together to form the “rungs of the DNA ladder they do so in a set pattern. The alternating sugar and phosphates make up the rails (backbone). The bases make up the rungs.

Adenine always bonds to Thymine (Two hydrogen bonds) Adenine always bonds to Thymine (Two hydrogen bonds) Guanine always bonds to Cytosine. (Three hydrogen bonds) Guanine always bonds to Cytosine. (Three hydrogen bonds) This bonding of bases is called Complementary Base Pairing. This bonding of bases is called Complementary Base Pairing. Cannot bond any other way because 2 purines would overlap and 2 pyrimidines would be too short to form the rungs of the ladder. Cannot bond any other way because 2 purines would overlap and 2 pyrimidines would be too short to form the rungs of the ladder.

The double strand is held in place by hydrogen bonds between the bases. It is the number and order as well as the type of the bases that determine what kind of organism will develop.

Example: ATCCGATT means something entirely different than ACCGTTAT, just as the words Hate and Heat mean different things even though they contain the same letters. Example: ATCCGATT means something entirely different than ACCGTTAT, just as the words Hate and Heat mean different things even though they contain the same letters. As a DNA strand lengthens, it twists into a double spiral called a Double Helix. As a DNA strand lengthens, it twists into a double spiral called a Double Helix.

Functions of DNA Functions of DNA 1. Replicates (duplicates) itself so each new cell has a complete, identical copy. 2. Controls the activities of a cell by producing proteins. The combination of proteins determines the characteristics (phenotype) of each living organism. 3. Undergoes occasional mutations. (Mistakes in replication) which accounts for the variety of living things on Earth. 3. Undergoes occasional mutations. (Mistakes in replication) which accounts for the variety of living things on Earth.

Steps in DNA Replication Steps in DNA Replication 1. The DNA molecule becomes untwisted by enzymes breaking the bonds. The 2 strands that make up DNA become unzipped. Each side acts as a template. (ie. The weak hydrogen bonds between the paired bases are broken by an enzyme)

2. New complementary nucleotides, always present in the nucleus, move into place and pair with complementary bases on the exposed strands. T joins to A C joins to G

3. The adjacent nucleotides, through their sugar-phosphate components become joined together along the newly forming chain. The enzyme DNA polymerase helps this. (Adds nucleotides to template).

4. When the process is finished, 2 complete DNA molecules are present, identical to each other and to the original molecule.

5. Both DNA will now wind back up into their helical shape. DNA replication is called semiconservative because each new double helix is composed of an old (parental) strand and a new (daughter) strand. DNA replication is called semiconservative because each new double helix is composed of an old (parental) strand and a new (daughter) strand. Enzymes assist the unwinding process, join together the nucleotides, and assist the rewinding process and many others. Enzymes assist the unwinding process, join together the nucleotides, and assist the rewinding process and many others. When errors are made in replication. A mutation can arise. When errors are made in replication. A mutation can arise.

Recombinant DNA Definition: DNA having genes from 2 different organisms, often produced in the laboratory by introducing foreign genes into a bacterial plasmid. Definition: DNA having genes from 2 different organisms, often produced in the laboratory by introducing foreign genes into a bacterial plasmid. Makes DNA Makes DNA A vector is used to introduce recombinant DNA. A plasmid is the most common vector (they are small rings of DNA founds in bacteria) A vector is used to introduce recombinant DNA. A plasmid is the most common vector (they are small rings of DNA founds in bacteria) The plasmid has to be removed from the bacteria and has to have a foreign gene inserted in. The plasmid has to be removed from the bacteria and has to have a foreign gene inserted in.

An enzyme (restriction enzymes) breaks the plasmid DNA. The new foreign DNA can now be attached to the plasmid. The enzyme, ligase, acts like glue and sticks the foreign DNA to the plasmid and makes it whole again. An enzyme (restriction enzymes) breaks the plasmid DNA. The new foreign DNA can now be attached to the plasmid. The enzyme, ligase, acts like glue and sticks the foreign DNA to the plasmid and makes it whole again.

The plasmid DNA is then put back into the bacteria. This bacteria will now replicate every cell the same as the one you just put in. Eventually there are many copies of the foreign gene.

Viral DNA can also be used as a vector to carry recombinant DNA into a cell. When a virus containing Recombinant DNA infects a cell, the viral DNA enters. Here it can direct the reproduction of many more viruses. Each virus derived from a viral vector contains a copy of the foreign gene, therefore viral vectors allows cloning of a particular gene. Viral DNA can also be used as a vector to carry recombinant DNA into a cell. When a virus containing Recombinant DNA infects a cell, the viral DNA enters. Here it can direct the reproduction of many more viruses. Each virus derived from a viral vector contains a copy of the foreign gene, therefore viral vectors allows cloning of a particular gene. Viral vectors are also used to create genomic libraries. Viral vectors are also used to create genomic libraries. Genomic library is a collection of engineered viruses that carry all the genes of a species. It takes about 10 million viruses to carry all the genes of a mouse. Genomic library is a collection of engineered viruses that carry all the genes of a species. It takes about 10 million viruses to carry all the genes of a mouse.

Summary Segments of DNA (particular genes) can be inserted into bacteria and the bacteria will go on its merry way and produce these genes. If desired genes are used – like those that produce certain chemicals (vaccines, antibodies, etc) then these proteins become much more available. Proteins hormones like insulin can be used using yeast cells. Interferon, a protein used in cancer treatments to help the immune system is now mass-produced this way. Segments of DNA (particular genes) can be inserted into bacteria and the bacteria will go on its merry way and produce these genes. If desired genes are used – like those that produce certain chemicals (vaccines, antibodies, etc) then these proteins become much more available. Proteins hormones like insulin can be used using yeast cells. Interferon, a protein used in cancer treatments to help the immune system is now mass-produced this way.

Uses of Recombinant DNA Generate DNA library, which will catalogue all the base sequences of known genes. Generate DNA library, which will catalogue all the base sequences of known genes. Identify specific genes. (In 1998, the gene that mutates to cause prostate cancer was identified) Identify specific genes. (In 1998, the gene that mutates to cause prostate cancer was identified) Produce synthetic copies of genes. Produce synthetic copies of genes. Insert genetic material into chromosomes that will help regulate cell function to make organism genetically “better”. Insert genetic material into chromosomes that will help regulate cell function to make organism genetically “better”.

DNA VS RNA Both are nucleic acids made up of nucleotides. DNA (Deoxyribonucleic Acid) RNA (Ribonucleic Acid) 1. Sugar is deoxyribose (5 carbon) Sugar is ribose (5 carbon) 2. Double stranded Single stranded 3. Found only in the nucleus Found in nucleus and cytoplasm. 4. Bases: Bases: A – AdenineA, C, G, but not T C– Cytosine Thymine is replaced by G – Guanine U – Uracil T – Thymine

Types of RNA: mRNA- Messenger RNA tRNA –Transfer RNA rRNA – Ribosomal RNA rRNA – Ribosomal RNA

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