Science - 3rd Periodical Exam

What is DNA

DNA

• Deoxyribonucleic acid is a long molecule that contains our unique genetic code. Like a recipe book it holds the instructions for making all the proteins in our bodies.  

• Your genome, is made of a chemical called deoxyribonucleic acid, or DNA for short.

• DNA contains four basic building blocks or bases; Adenine (A), Cytosine (C), Guanine (G), and Thymine (T)

  • the order of these bases form the instructions in the genome.

• DNA is a two-stranded molecule

• DNA has a unique ‘double helix’ shape, like a twistedladder.

Some infos

• Eachstrand is composed of long sequences of the fourbases, A, C, G and T. The bases on one strand of the DNA molecule pair together with complementarybases on the opposite strand of DNA to form the ‘rungs’ of the DNA ‘ladder’

• The bases always pair together in the same way, A with T, C with G. Each base pair is joined together by hydrogen bonds. Each strand of DNA has a beginning and an end, called 5’ (five prime) and 3’ (three prime) respectively.

• The two strands run in the opposite direction (anti-parallel) to each other so that one runs 5’ to 3’ and one runs 3’ to 5’, they are called sense strand and the antisense strand. The strands are separated during DNA replication.

• This double helix structure was first discovered by Francis Crick and James Watson with the help of Rosalind Franklin and Maurice Wilkins.

• The human genome is made of 3.2 billion bases of DNA but other organisms have different genome sizes.

Deoxyribonucleic acid is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses. DNA and ribonucleic acid are nucleic acids.

What is DNA made of?

• DNA is shaped like a spiral staircase

• The handrails of the staircase are made of nucleotides

• The steps of the staircase are made of bases.

• There are 4 bases used in the DNA molecule, and each pairs with another.

What is RNA?

• RNA, ribonucleic acid, complex compound of high molecular weight that functions in cellular protein synthesis and replaces DNA (deoxyribonucleic acid) as a carrier of genetic codes in some viruses. RNA consists of ribose nucleotides (nitrogenous bases appended to a ribose sugar) attached by phosphodiester bonds, forming strands of varying lengths. The nitrogenous bases in RNA are adenine, guanine, cytosine and uracil, which replaces thymine in DNA.

• RNA is a single-stranded nucleic acid polymer of the four nucleotides A, C, G, and U joined through a backbone of alternating phosphate and ribose sugar residues.

• It is the firstintermediate in converting the information from DNA into proteins essential for the working of a cell.

• Some RNAs also serve directroles in cellular metabolism. RNA is made by copying the base sequence of a section of double-stranded DNA, called a gene, into a piece of single-stranded nucleic acid. This process, called transcription (see below RNA metabolism), is catalyzed by an enzyme called RNA polymerase.

• Ribonucleic acid - a type of nucleic acid

• R = ribose (a type of sugar)

• single stranded

• can be found inside or outside of the nucleus

• made of monomers (building blocks) called nucleotides. Each nucleotide has a sugar, phosphate, and nitrogenous base.

Structure of DNA

• DNA's unique structure enables the molecule to copy itself during cell division.

• When a cell prepares to divide, the DNA helix splits down the middle and becomes two single strands.

• These single strands serve as templates for building two new, double-strandedDNA molecules - each a replica of the original DNA molecule

• DNA is made up of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base.

How protein is made using DNA

•  First, enzymes read the information in a DNA molecule and transcribe it into an intermediary molecule called messenger ribonucleic acid, or mRNA.

• Next, the information contained in the mRNA molecule is translated into the "language" of amino acids, which are the building blocks of proteins.

What is a protein?

• Proteins are the major ‘working molecules’ within every organism. Among their many jobs, proteins catalyse reactions, transport oxygen and defend organisms from infection. They’re also crucial building blocks of organisms. They are the major components of wool, cartilage and milk, they package up the DNA in chromosomes and they insulate the cells of the nervous system. In short, proteins are hugely important!

• Proteins are made of large numbers of amino acids joined end to end. The chains fold up to form three-dimensional molecules with complex shapes – you could think of it as origami with a very long and thin piece of paper. The precise shape of each protein, along with the amino acids it contains, determines what it does.

Proteins are made from genes

All organisms make proteins in essentially the same way. The process starts with a gene – the ‘instruction manual’ for constructing the protein. For this reason, the process of making a protein is also called gene expression.

Gene expression has two main stages: transcription and translation.

Transcription

• Structures in the cell identify the start and end of a gene and read the DNA sequence between them (the order of A, C, G and T bases within the gene). A molecular message (an mRNA molecule

• Two or more atoms bonded together. The molecule of an element has all its atoms the same. The molecule of a compound has two or more different atoms.

• ) is produced that echoes the sequence of the gene itself. In most respects, mRNA looks similar to a single-stranded piece of DNA.

Translation

• A ribosome receives the mRNA molecule and starts to build a chain of amino acids (a protein) that exactly matches the instructions within the mRNA. The ribosome ‘reads’ the mRNA sequence as a series of three-base chunks or codons. Each codon tells the protein-making machinery which amino acid to add next.

Summary;

Translation: Using mRNA to make a protein

• DNA is found in nucleus

• mRNA is made in the nucleus from DNA template

• mRNA carries the message to the ribosome

• Protein is made using mRNA code like a “recipe” and amino acids as “ingredients”

Overview: Using DNA to make proteins

• DNA - stays in the nucleus

  • copies itself and gets passed on to new cells

  • holds instructions for making proteins

• RNA - made in the nucleus and goes to the cytoplasm

  • uses DNA instructions to make proteins

• Protein - used as body structures (muscle, bone, skin, hair), enzymes, transporters, hormones, etc.

• Trait - observable characteristic

  • who you are.

How proteins are made?

• mRNA copies the DNA code inside the nucleus

• mRNA carries the code from the nucleus to a ribosome

• at a ribosome, amino acids are placed in the order relating to the code

• amino acids join together to make a protein