Chapter Six: Genes and DNA
Section One: What Does DNA Look Like?
Vocabulary
DNA- deoxybribonucleic acid, a molecule that is present in all living cells and that is present in all living cells and that contains the information that determines the traits that a living thing inherits and needs to live
Nucleotide- in a nucleic-acid chain, a subunit that consists of a sugar, a phosphate, and a nitrogenous base
Chapter Five; Section One: Summary
Adenine only pairs with thymine and guanine only pairs with cytosine.
Section one was about DNA. Genes must be able to build and maintain cells and be able to copy each time a cell divides. The bases of a nucleotide are adenine, thymine, cytosine, and guanine. Erwin Chargaff, a biochemist, discovered adenine and thymine are equal amounts and guanine and cytosine are equal amounts. Rosalind Franklin, a chemist, used X-ray diffraction on a DNA molecule. The rays bounced off the molecule and she recorded the pattern and suggested DNA had a spiral shape. James Watson and Francis Crick used Rosalind Franklin's X-ray images to conclude DNA has a spiral shape. The spiral shape is called a double helix. Correct bases only fit in DNA's ladder width. Both sides of the DNA molecule are complementary, meaning pairs of bases go well together. The sequence GCAT is complementary to the sequence CGTA. Copies of DNA are made when the cell divides. To begin copying, the DNA molecule splits down the middle. Then complementary nucleotides pair with the old side. Now there are two there are two DNA strands.
Section Two: How DNA works
Vocabulary
RNA- ribonucleic acid , a molecule that is present in all living things and that plays a role in protein production
Ribosomes- a cell organelle composed of RNA and protein; the site of protein synthesis
Mutation- a change in the nucleotide-base sequence of a gene or DNA molecule
Chapter Six, Section Two: Summary
These are genetically engineered strawberries.
Section two was about DNA and RNA. DNA is wound around proteins, coiled into strands, then it is bundled even more. In prokaryotic cells DNA strands form a loose loop within the cell in eukaryotic cells DNA strands and proteins are bundled into chromosomes. DNA's structure allows it to hold information. Genes consist of nucleotide strings that give a cell information about how to make a specific trait. groups of three bases form a specific code for an amino acid. For example the bases CCA is the code for the amino acid proline. Proteins cause most of the differences you can see in organisms. Proteins act as chemical trigger and messengers for many processes in the cell. One organism can have thousands of genes that code for thousands of proteins. RNA can serve as a temporary DNA sequence. RNA helps in the process of changing DNA code into proteins. The first step of making a protein is copying one side of a DNA segment containing a gene.The copy is made of RNA. The segment is called messenger RNA (mRNA). It then moves out of the nucleus into the cytoplasm. The mRNA runs through ribosomes. Ribosomes are made of RNA and protein. The mRNA is fed through the ribosomes three bases at a time. Molecules of transfer RNA (tRNA) translate the mRNA. The tRNA pick up amino acids in the cytoplasm. The tRNA match up with mRNA in the ribosome. The tRNA release their amino acids. The amino acids link in a chain. The chain then folds into a new protein molecule.
Mutations are changes in a DNA sequence. When a base is added it is called an insertion. When a base is left out it is called a deletion. When a base is changed it is called a substitution Sometimes a mutation are helpful, harmful, or have no affect on an organism. Any physical thing that causes a mutation is called a mutagen. Asbestos, cigarettes, ultra violet radiation are mutagens. A simple change in an amino acid can cause a disease. Scientists can also genetically change an organism. They can make new products such as food or fabric. Scientists also use DNA for crime scenes. They can use a person's finger print to identify them. Scientists can create clones which are exact copies of an organism. It's not a twin because it doesn't happen naturally.
Mutations are changes in a DNA sequence. When a base is added it is called an insertion. When a base is left out it is called a deletion. When a base is changed it is called a substitution Sometimes a mutation are helpful, harmful, or have no affect on an organism. Any physical thing that causes a mutation is called a mutagen. Asbestos, cigarettes, ultra violet radiation are mutagens. A simple change in an amino acid can cause a disease. Scientists can also genetically change an organism. They can make new products such as food or fabric. Scientists also use DNA for crime scenes. They can use a person's finger print to identify them. Scientists can create clones which are exact copies of an organism. It's not a twin because it doesn't happen naturally.
Now that you know about genes and DNA, here is a song about DNA.