7.1 DNA and RNA
The Central Dogma: This explains how the information to make proteins is carried: DNA RNA proteins
Discovering DNA It was not always known that DNA contains all of the genetic material. These researchers all helped to identify DNA: Frederick Griffith Oswald Avery Alfred Hershey and Martha Chase Erwin Chargaff James Watson and Francis Crick (and Rosalind Franklin) Figured out that DNA is a double helix shape
Erwin Chargaff mid-1900s Studied properties of DNA and saw that DNA has 4 nitrogen bases: 1. Adenine (A) 2. Guanine (G) 3. Cytosine (C) 4. Thymine (T) Developed Chargaff s rules: Same amounts of adenine (A) and thymine (T) in DNA (A-T) Same amounts of cytosine (C) and guanine (G) in DNA (C-G)
Watson, Crick, & FRANKLIN James Watson and Francis Crick are credited with discovering the double-helix shape of DNA However, they stole the information from Rosalind Franklin. They were only able to figure out the double-helix shape after they looked at the pictures Franklin took.
What is DNA? DNA is responsible for the functions of all living things. The genetic material found in your cells Determines your characteristics and codes for proteins Proteins are the molecules that make the cells of all living things work. The information needed to create a protein is written in DNA. Without DNA, a cell could not create proteins. Without proteins, a cell could not function. DNA Structure & Function
DNA is made from 3 key ingredients What is DNA made from? 1. A base: there are four kinds of bases Adenine (A), Thymine (T), Cytosine (C), and Guanine (G) 2. Sugar molecules 3. Phosphate molecules phosphate Sugar and phosphate together form the backbone of the DNA molecule and hold the bases in place. DNA is made up of 2 strands (double helix) deoxyribose bases
Bases The bases in DNA are the molecules that actually create the code a cell reads in order to create a protein. There are 4 kinds of bases in DNA: adenine, thymine, cytosine, and guanine. The 4 bases are abbreviated by their first letter: A, T, C, G The combinations of these four bases are what create the genetic code.
DNA Structure DNA has 2 strands Each strand is made up of bases, sugars, and phosphates Each strand has a complementary base pair which connects the two strands
DNA Replication When the cell needs to copy its DNA, it will need to open up the DNA to read it. When DNA is in its ladder version, it is not able to be read. The DNA must first be opened in order to read it. The cell opens DNA using an enzyme This enzyme is a protein that opens DNA in the same way that your zipper tab opens a zipper.
Once DNA is opened, it can be duplicated (copied).
DNA Replication Steps Helicase unwinds DNA SSB proteins hold DNA open Primase adds primers to the DNA DNA Polymerase builds the DNA Ligase glues DNA segments together in the lagging strand only Segments = Okazaki fragments
How DNA is Copied A pairs with T C pairs with G Example: AGC TAG GAT CGA TTG TCA GCT TAG CTA TCG ATC CTA GCT AAC
Why do we care about DNA? DNA gives us options. By known how DNA works and how to change it, we can create more opportunities, including Make medicine from plants, animals, and other organisms Replacement of diseased or damaged organs (such as hearts or spinal cords) And many more!
RNA Stands for ribonucleic acid Once DNA has been replicated (copied), RNA is needed to read the DNA and tell the body which proteins to make DNA stays in the nucleus, but proteins are made on ribosomes in the cytoplasm of the cell RNA is needed to get information from DNA in nucleus to ribosomes in the cytoplasm
RNA vs. DNA RNA DNA Single strand Has uracil (U) instead of thymine (T) A-U Ribose Leaves the nucleus Double stranded Uses thymine (T), not uracil A-T Deoxyribose Stays in the nucleus
Types of RNA Messenger RNA (mrna) Carries info from DNA to the cytoplasm Ribosomal RNA (rrna) Helps make ribosomes Transfer RNA (trna) Used to make proteins
Videos DNA Structure & Function DNA Replication