What do I know about DNA 4 th

What do I know about DNA? 4 th period DNA means deoxyribonucleic acid early 1900’s—not thought very important because so simple DNA is inherited from your parents—basis for genetics discovered in 1940’s Mutations mess up DNA & can cause birth defects or diseases discovered in 1970’s DNA is passed in sex cells discovered in 1950’s DNA makes up chromosomes-we have 20 something It’s twisty—like a twisted ladder—called a double helix Discovered 1951 nobel prize

What do I know about DNA? 5 th period DNA is found in the nucleus You can identify a person by DNA analysis—unique for every person Double helix structure DNA is needed to make proteins DNA controls everything happening in cell Each child’s DNA comes from the parents basis of genetics parent’s got it from their parents sex passes it on

DNA Structure and Replication Notes February 25, 2021

http: //www. hhmi. org/biointeractive/ double-helix Who discovered dna?

Questions 4 th period Why do older women have more babies with birth defects? Why can blond mom and dad have red head kid?

DNA Structure Notes http: //www. hhmi. org/biointeractive/chemical -structure-dna

Extract DNA from a strawberryhttps: //www. youtube. com/watch? v=v. PGKv 53 z. SRQ Pour DNA extract solution (dishwashing soap, Na. Cl, distilled water) into a sealable plastic bag with a strawberry. Seal … no leaks! Gently mash strawberry until it’s a smooth solution. (5 minutes) Line a funnel w/ cheesecloth, then filter mashed strawberry into a tube; mash juice but not chunks through cheesecloth. Throw out cloth; wash funnel. Gently layer (pour slowly down side of angled tube) cold alcohol onto top of strawberry solution. Watch 2 minutes as strands of DNA (chromosomes, each millions of nucleotides long!) rise into the top layer. Pull out some of the DNA with a plastic pipet, then add it to the class flask that is filled with alcohol (to make the DNA easier to see) Pour remaining solution down sink, rise tubes/stoppers & place in dish tray.

I. Functions of DNA = “Blueprint of Life” • Storing Information – Store the genes that code for basic instructions for cells and cell parts, physical traits, diseases, etc. • Eye color, blood type, skin color, diabetes, etc. • Copying Information – Before a cell divides, it must make a copy of every one of its genes • Process called DNA replication • Transmitting Information – Genes are transmitted from one generation to the next • DNA must be carefully sorted and passed along during mitosis and meiosis

II. Basics of DNA Structure A. DNA - stands for deoxyribonucleic acid B. double-stranded C. 3 -D model is called = double helix – Discovered by James Watson & Francis Crick (Received Nobel Prize 1962) with the help of Rosalind Franklin’s data

Long double helices of DNA, each millions of nucleotides long, form chromosomes. Each chromosome contains hundreds of genes. Humans cells have 46 chromosomes.

III. Nucleic Acid Structure A. DNA is a type of molecule called a nucleic acid B. The building blocks of DNA are known as nucleotides 1. All nucleotides have three “parts” in common: a. Phosphate b. Sugar (deoxyribose) c. Nitrogen base

NUCLEOTIDE

B. Nitrogen Bases 1. Four types: a. Adenine b. Guanine c. Cytosine d. Thymine 2. The order of these bases = the genetic code!

Complementary Base Pairing 1. A-T and C-G pairs are the only ones physically possible 2. Hydrogen bonds between nitrogen bases 2. Adenine and Thymine must form two hydrogen bonds to be stable while Guanine and Cytosine must form three hydrogen bonds

LET’S PRACTICE! Write the complementary sequence of bases to this strand of DNA. A T C C G G A T

DNA Structure (more details) • Sugar/Phosphate “Backbone” – Sides of ladder – Covalent bond between sugar and phosphate • Nitrogen Bases in center – Steps of ladder – Hydrogen bond between Nitrogen bases • Double Helix – Twisted ladder • Anti-parallel – two strands of DNA run in opposite directions

DNA is Anti-Parallel The two strands of DNA run in opposite directions This allows for the bases to come in contact at the center of the molecule

DNA Replication Notes February 25, 2021

I. DNA Replication A. Purpose 1. All cells must divide to make new cells 2. Before cell division DNA is replicated so it can be passed to the new cell 3. This process of copying the DNA in the chromosomes is called DNA Replication 4. Without this process, new cells would have only half the DNA of their parents

Each new DNA molecule has one original “parent” strand one new strand!

B. Process of DNA Replication 1. Occurs in the nucleus prior to any cell division 2. Enzyme is used to “unzip” or “unwind” the DNA into two single strands a. Enzyme breaks hydrogen bonds between nitrogen bases b. This occurs along several sections of the whole molecule of DNA Enzyme

B. Process of DNA Replication (cont. ) 1. Another enzyme, DNA polymerase, bonds a complementary nucleotide to each strand of template DNA 2. Nitrogenous bases pair up 1. A – T 2. C - G 3. Each strand is replicated in opposite directions, since DNA is anti-parallel 4. Process continues until the entire strand of DNA has been unzipped and replicated

B. Process of DNA Replication (cont. ) As a result, you create two new molecules of DNA that are identical to the original piece of parent DNA Each DNA molecule has a new strand of DNA and an old strand of DNA (parent DNA)