Chapter 6 life science

1. Chapter 6 life science Genes and DNA

2. Section 1what does DNA look like? • Inherited characteristics are determined by genes • Genes are found on the chromosomes • Chromosomes are made of Proteins and DNA • DNA (deoxyribonucleic acid) contains the information that determines traits of organisms. • DNA is made of subunits called nucleotides. • A nucleotide consists of a sugar, a phosphate, and a base. • The four bases are adenine thymine, guanine, and cytosine. • Each base has a different shape. • The bases are referred to by their first letter A,T, G, and C. • In the 1950’s, Erwin Chargaff found that the amount of adenine always equals the amount of thymine and the amount of cytosine always equals the amount of guanine. • later the structure of DNA was discovered through X ray diffraction by Rosilind Franklin.

3. Section 1 page 2 • James Watson and Francis Crick concluded that DNA was shaped like a twisted ladder. • Using simple materials, the two built a double helix model of DNA. • The two sides of the ladder represent alternating sugar and phosphate parts. • The rungs of the ladder represent paired bases. • Adenine (A) always pairs with thymine (T) • Cytosine (C) pairs with guanine (G). • This made the strands complimentary: CGAT would be paired with GCTA. • Copying of DNA strands is called replication, (the DNA strands splits and the bases make a complimentary copy to form a new strand) • DNA is copied each time a cell divides.

4. DNA models

5. Section 2how DNA works • Each gene is usually a set of instructions to make a specific protein. • Proteins act as chemical triggers and messengers for many of the processes of a cell. • Proteins help determine how tall you are , what color hair and eyes you have, and how well you see. • Another material that helps make proteins is ribonucleic acid (RNA). • RNA is very similar to DNA and can serve as a temporary copy of a DNA sequence. • The factory that runs the copying process is a ribosome. • RNA is what allows these puzzle pieces to match up when a cell divides and copies itself to be passed on to another organism. • During replication, changes can occur in a gene. These changes are called mutations. Mutations can be helpful or harmful. • One mutation is called insertion. An extra base is added in the stand.

6. Section 2 page 2 • If a base is left off the code, it is called deletion. • If a mutation is found on a sex cell, it is passed to the next generation. And example in humans is albinism ( the lack of pigment in skin) • Mutations happen randomly or can be caused by a mutagen. • Mutagens include radiation or exposure to chemicals. • Another mutation called substitution occurs if the wrong base is inserted into a sequence. • Sickle cell anemia is an example that causes blood cells to have an abnormal shape. This disorder can cause severe and painful blood clots to form. • Scientists have learned to manipulate genes through genetic engineering. • DNA fingerprinting allows people to be identified through crime scene investigations and also is used in the process of creating organism called cloning.

7. Daily assignment Page 147 # 3-8 Page 155 # 3-5, 7-11 Pages 158 – 159 # 2-14, 16-22