How Traits Change - Part 1 PDF

How Traits Change - Part 1 Unit 1 Module 2: Natural Selection and Adaptations Ms. Nour Kabbara Table of contents Introduction to DNA Replication Transcription Translation How does DNA affect traits? Introduction An organism’s body cells use codes to determine gene...

How Traits Change - Part 1 Unit 1 Module 2: Natural Selection and Adaptations Ms. Nour Kabbara Table of contents Introduction to DNA Replication Transcription Translation How does DNA affect traits? Introduction An organism’s body cells use codes to determine genetic traits. Cells put molecules together by following a set of directions. Genes provide the directions for a cell to put together molecules that express traits, such as eye color or seed shape.  The Structure of DNA Chromosome DNA Chromosomes are made of DNA is an organism’s proteins and deoxyribonucleic genetic material. acid, or DNA. Gene A gene is a segment of DNA Chromosome on a chromosome. DNA Scientists estimate there is over 1 m of DNA in a human cell. How does it fit in such a small space?  The Structure of DNA Strands of DNA in a chromosome are tightly coiled, like a coiled spring. This coiling makes it possible for more genes to fit in a small space.  A Complex Molecule The shape of DNA is like a twisted ladder. It is called a double helix.  Discovery of DNA Rosalind Franklin An American scientist, Watson worked with and Maurice Wilkins James Watson, visited English scientist were two scientists Franklin and Wilkins. Francis Crick to build in London. They Watson saw one of the a model of DNA. used x-rays to DNA x-rays. The model showed study DNA. Some of He realized that the x- how smaller the x-rays showed ray gave valuable clues molecules of DNA that DNA has a about the structure of bond together and helix shape. DNA. form a double helix.  Discovery of DNA Franklin's X-Ray of DNA Watson and Crick model of DNA  Four Nucleotides P Shape DNA A nucleotide is a molecule SUGAR made of a nitrogen base, a sugar, and a phosphate group. Label parts of a nucleotide A closer look  Each nucleotide is Nitrogen bases Sugar-phosphate made of a nitrogen form the teeth of groups form the base, a sugar, and a the helix sides of the helix phosphate group  What is stored in DNA? It is the information, or directions, needed for an organism to grow, maintain itself, and reproduce. Replication  DNA replication process Cells contain DNA in chromosomes. So, every time a cell divides, all chromosomes must be copied for the new cell. The new DNA is identical to existing DNA. Replication is the process of copying a DNA molecule to make another DNA molecule.  DNA strand 1) DNA strand separates and nitrogen bases are exposed. Nitrogen Bases  Nucleotide 2) Nucleotides move into place and form new nitrogen base pairs 3) Two identical strands of DNA are produced.  Making Proteins Proteins are important for every cellular process. Making Proteins Most genes contain instructions for making proteins. Some genes contain The DNA of each instructions for when cell carries a and how quickly complete set of proteins are made. This set of genes. genes provides instructions for making all the proteins a cell needs. The Role of RNA in Making Proteins Proteins are made with the help of ribonucleic acid.  1.How are DNA and RNA similar? 2.What are the key differences between DNA and RNA?  Answers: 1) RNA, like DNA, is made of nucleotides. 2) The key differences between DNA and RNA are: ○ RNA is single-stranded, while DNA is double-stranded. ○ RNA has the nitrogen base uracil (U), while DNA has thymine (T). ○ RNA has the sugar ribose instead of the sugar deoxyribose, which is found in DNA. Types of RNA  Types of RNA 1.Messenger RNA (mRNA) 2.Transfer RNA (tRNA) carries the code for making carries amino acids proteins from the nucleus to around inside a cell. the cytoplasm. 3.Ribosomal RNA (rRNA) forms a part of ribosomes. Transcription  Transcription The first step in making a protein is to make mRNA from DNA. Transcription is the process of making mRNA from DNA. Translation  Translation Translation is the process of making a protein from RNA. Translation occurs as mRNA moves through a ribosome. Recall that ribosomes are cell organelles that are attached to the rough endoplasmic reticulum (rough ER). Ribosomes are also in a cell’s cytoplasm. 1) tRNA carries amino acids to the ribosome. 2) rRNA helps form chemical bonds that attach one amino acid to the next. 3) The first tRNA separates from its animo acid and from the mRNA. A third tRNA brings in another amino acid.  Translating the RNA Code Making a protein from mRNA is like using a secret code. Proteins are made of amino acids. The order of the nitrogen bases in mRNA determines the order of the amino acids in a protein. Three nitrogen bases on mRNA form the code for one amino acid. Each series of three nitrogen bases on mRNA is called a codon. The End!