DNA The Code of Life

Introduction… DNA RNA There are two types of nucleic acids… Deoxyribonucleic acid This makes up the genes located on the chromosomes in the nucleus. RNA Ribonucleic acid This is formed in the nucleus BUT functions in the cytoplasm.

Structure of Nucleic Acids Both DNA and RNA are large molecules. They are made up of a number of smaller units or monomers called nucleotides. Each nucleotide is made up of: A nitrogenous base (NB) A sugar portion (S) Deoxyribose in DNA Ribose in RNA A phosphate portion (P)

Structure of Nucleotide Each nucleotide is made up of: A nitrogenous base (NB) A sugar portion (S) Deoxyribose in DNA Ribose in RNA A phosphate portion (P) P NB S

DNA Location of DNA Structure of DNA Functions of DNA

DNA: Location of DNA The DNA within the nucleus is called NUCLEAR DNA. Together with proteins, it makes up the chromosomes which in turn go to make up the chromatin network. Small amounts of DNA are also found outside the nucleus (extra-nuclear DNA) such as: Within chloroplasts (called chloroplastic DNA) Mitochondria (called mitochondrial DNA or mtDNA)

DNA: Structure of DNA Structure was discovered by James Watson and Francis Crick in 1953. DNA is double stranded i.e. it consists of two strands of nucleotides joined together by weak hydrogen bonds. The natural shape of DNA is a double helix. Each DNA nucleotide contains the sugar – deoxyribose.

DNA: Structure of DNA There are 2 groups of nitrogenous bases: purines and pyrimidines. Purines = adenine and guanine (PUAG) Pyrimidines = cytosine and thymine (PYCTH) The nitrogen bases are complementary: Cytosine ONLY with guanine Adenine ONLY with thymine

Deoxyribose Purines: Adenine Guanine NB S Pyrimidines: Cytosine DNA: Structure of DNA Purines: Adenine Guanine P NB S Pyrimidines: Cytosine Thymine Deoxyribose

Basic double helix of DNA DNA: Structure of DNA Basic double helix of DNA

DNA: Structure of DNA

DNA: Functions of DNA DNA codes for the formation of different proteins required in the body. DNA is responsible for transmitting hereditary characteristics form parents to offspring.

RNA Location of RNA Structure of RNA Functions of RNA

RNA: Location of RNA There are 3 types of RNA: Ribosomal RNA (rRNA) found in the ribosomes in the cytoplasm of the cell. Messenger RNA (mRNA) which is found in the nucleus and attaches to the ribosome in the cytoplasm. Transfer RNA (tRNA) found in the cytoplasm of the cell.

RNA: Structure of RNA Ribonucleic Acid (RNA) is similar to DNA except that: It is a single stranded structure. The sugar in it is RIBOSE. Thymine is replaced by URACIL. The bases are not paired.

RNA: Functions of RNA All three types of RNA play important roles in PROTEIN SYNTHESIS.

Similarities between DNA and RNA Both contain sugar alternating with phosphate. Both contain the nitrogenous bases ADENINE, GUANINE and CYTOSINE. Both play a role in protein synthesis.

Similarities between DNA and RNA Found in the nucleus, chloroplast and mitochondria. Double stranded molecule. Contains the sugar deoxyribose. Contains the nitrogenous base thymine. Found in the nucleus and cytoplasm. Single stranded molecule. Contains the sugar ribose. Contains the nitrogenous base uracil.

Similarities between DNA and RNA Found in the nucleus, chloroplast and mitochondria. Double stranded molecule. Contains the sugar deoxyribose. Contains the nitrogenous base thymine. Found in the nucleus and cytoplasm. Single stranded molecule. Contains the sugar ribose. Contains the nitrogenous base uracil.

Similarities between DNA and RNA

Similarities between DNA and RNA

DNA Replication

DNA Replication What is DNA replication? When does it occur? The process by which DNA makes an identical copy of itself. When does it occur? DNA replication occurs just before cell division (mitosis and meiosis). It occurs during interphase. Why does it occur? DNA replication is a process by which identical copies of DNA are made so that it could be shared amongst the daughter cells during cell division so that each daughter cell has the same number of chromosomes as the original. It allows the daughter cells after mitosis to be identical to each other and to the cell from which they were formed.

DNA Replication HOW DOES IT OCCUR? Double helix DNA unwinds. Weak hydrogen bonds between nitrogenous bases break. Two DNA strands unzip/separate. Each original DNA strand serves as a template to form a new strand by attaching to free nucleotides from the nucleoplasm. This forms complementary strands (A to T and C to G). Each DNA molecule now consists of 1 original strand and 1 new strand. The result is two genetically identical DNA molecules. The entire process is controlled by enzymes.

http://www.hhmi.org/biointeractive/dna-replication-advanced-detail

DNA Profile What is a DNA profile? DNA profiles are patterns of black bars left on X-Ray film when an extract of DNA is put through a special biotechnical process. This is called PCR (Polymerase Chain Reaction) DNA profiling is a method of identifying an individual by comparing his/her DNA profile with another known DNA profile.

DNA Profile What are the uses of DNA Profiles? DNA profiles are used for: The diagnosis of inherited disorders such as cystic fibrosis, haemophilia and sickle cells anaemia. Identificaiton of criminals in forensic science. Identification of relatives such as: Establishing whether a particular person is the father of a child or not. Tracing siblings (brothers and sisters) who have been separated at birth. Identifying people who have died and where their bodies cannot be recognised.

DNA Profile Debates around DNA Profiling The small piece of DNA may NOT be unique to an individual Uniform testing standards & quality controls may be lacking in private laboratories Human error could occur during interpretation of the results DNA profiling is expensive Profiling may reveal personal information like HIV which could lead to prejudice

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