GENETICS DNA Basics

What are these two creatures? …the mammals. Which species weighs more? Use your personal technology to find out.

What are their scientific names? Ursus arctos Ursus maritimus

What makes them different? DNA

Distinguish between DNA and RNA Standard SB2a Distinguish between DNA and RNA

A little history lesson…

Rosalind Franklin…

And now…the notes.

DNA: The Molecule of Heredity DNA = Deoxyribonucleic acid; a type of nucleic acid The building blocks (monomers) of DNA are nucleotides A nucleotide is composed of: Deoxyribose (a sugar compound) A phosphate group A nitrogen base Ringed compound that contains Nitrogen

Nitrogen bases in DNA In DNA, there are four possible Nitrogen bases Adenine Guanine Cytosine Thymine

The Double Helix The three parts of DNA (sugar, phosphate, and nitrogen base) come together to form NUCLEOTIDES The nucleotides will link together to form two long strands The two strands will connect at the nitrogen bases and twist forming a DOUBLE HELIX The linking occurs with “complimentary base pairing”… Adenine will pair with Thymine Guanine will pair with Cytosine The link that holds the bases together is a Hydrogen bond

Let’s Practice… A-T-C-C-G-A-T-A-C is one strand of a double stranded DNA sequence. Write the complimentary DNA strand. A-T-C-C-G-A-T-A-C ║ ║ ║ ║ ║ ║ ║ ║ ║ T-A-G-G-C-T-A-T-G

DNA Double Helix

Chargaff’s Rule… Erwin Chargaff (1950) determined that in any strand of DNA: % purines = % pyrimidines %A = %T %C = %G #A+T ≠ #C+G

Practice Problem… A DNA sample was found to have 24% Adenine. What will be the percentages of Cytosine, Guanine and Thymine in this sample?

Practice Problem 2 In a particular sample of DNA, there are 17%G. Determine the percentages of the other bases in this sample.

Practice Problem 3 A sample of DNA taken from a crime scene is found to have 200 base pairs (400 bases). Of the bases, 120 are Thymine. Determine the numbers and percentages of the other 3 bases.

Practice Problem 4 A sample of DNA taken from a recruit at indoc into the Army is found to have 40 base pairs (80 bases). Of the bases, 22 are Guanine. Determine the numbers and percentages of the other 3 bases.

Prokaryotic DNA The DNA in bacteria is different from the DNA in eukaryotic cells. In bacteria, the DNA is a single circular strand of DNA. Kind of looks like “spaghetti-ohs”.

RNA vs DNA There are THREE main differences between DNA & RNA The sugar In DNA it’s DEOXYribose sugar In RNA it’s Ribose sugar Number of strands DNA is usually double stranded RNA is ONLY single stranded Nitrogen Bases DNA Adenine pairs with Thymine Guanine pairs with Cytosine RNA Adenine pairs with Uracil

Why DNA? Segments of DNA code for proteins Each set of three base pairs codes for a particular amino acids The three bases are called the codon Amino acids are the building blocks for proteins Since 3 bases pairs are involved, the DNA code is often called the triplet code There are 64 possible codon combinations given the four nitrogen bases combined into triplets

DNA & Chromosomes When comparing the chromosomes of two different organisms, you’ll find that both contain DNA with the same bases The ORDER of the nucleotides is what makes the organisms different The more closely related two organisms are, the more alike their order of nucleotides will be.

Genes & Chromosomes Genes Chromosomes Small pieces of DNA that code for a specific trait Chromosomes Collection of genes that are wound in the shape of an X (when ready for cell division) Half of a chromosome – a chromatid

Video… Bozeman Video…

Review: Which of the following is the monomer of DNA? A.) phosphate group B.) nucleotide C.) RNA D.) deoxyribose

B.) nucleotide Review: Which of the following is the monomer of DNA? A.) phosphate group B.) nucleotide C.) RNA D.) deoxyribose

Review Nucleotides are made of: A.) a sugar B.) a phosphate group C.) a nitrogen base D.) all of the above

D.) all of the above Review Nucleotides are made of: A.) a sugar B.) a phosphate group C.) a nitrogen base D.) all of the above

Review The people credited with discovering DNA’s structure are: A.) Avery and Chase B.) Mendelsohn and Stahl C.) Watson and Crick D.) All of the above

C.) Watson and Crick Review The people credited with discovering DNA’s structure are: A.) Avery and Chase B.) Mendelsohn and Stahl C.) Watson and Crick D.) All of the above

Review Which of the following is not found in DNA? A.) Deoxyribose B.) Phosphate C.) Adenine D.) Protein

D.) Protein Review Which of the following is not found in DNA? A.) Deoxyribose B.) Phosphate C.) Adenine D.) Protein

Review The sides (backbone) of DNA are made of: A.) Deoxyribose sugar and adenine B.) complete nucleotides C.) sugar and phosphate D.) Nitrogen bases, sugar and phosphate

C.) sugar and phosphate Review The sides (backbone) of DNA are made of: A.) Deoxyribose sugar and adenine B.) complete nucleotides C.) sugar and phosphate D.) Nitrogen bases, sugar and phosphate

Review In DNA, Adenine bonds with: A.) Adenine B.) Guanine C.) Cytosine D.) Thymine

D.) Thymine Review In DNA, Adenine bonds with: A.) Adenine B.) Guanine C.) Cytosine D.) Thymine

Review What holds one base to another? A.) hydrogen bonds B.) the sugar C.) phosphate groups D.) ionic bonds

A.) hydrogen bonds Review What holds one base to another? B.) the sugar C.) phosphate groups D.) ionic bonds

Review The following is one side of a DNA strand: A-T-G-T-C-C-A-T Which of the following would be the complementary (other side of the )DNA strand? A.) A-T-G-T-C-C-A-T B.) T-A-C-A-G-G-T-A C.) T-T-G-G-A-C-A-T D.) A-A-G-A-G-G-T-A

B.) T-A-C-A-G-G-T-A Review The following is one side of a DNA strand: A-T-G-T-C-C-A-T Which of the following would be the complementary (other side of the )DNA strand? A.) A-T-G-T-C-C-A-T B.) T-A-C-A-G-G-T-A C.) T-T-G-G-A-C-A-T D.) A-A-G-A-G-G-T-A

Review Which of the following could be a nucleotide of DNA? A.) Deoxyribose, uracil, phosphate B.) Ribose, adenine, phosphate C.) Adenine, Thymine, phosphate D.) Guanine, phosphate, deoxyribose

D.) Guanine, phosphate, deoxyribose Review Which of the following could be a nucleotide of DNA? A.) Deoxyribose, uracil, phosphate B.) Ribose, adenine, phosphate C.) Adenine, Thymine, phosphate D.) Guanine, phosphate, deoxyribose