The fingerprint that’s inside your body!!!!!! DNA The fingerprint that’s inside your body!!!!!!

You can tell people apart by their fingerprints… Because everyone’s fingerprints are different! So is your DNA!

DNA

MCAS objectives Describe the basic structure of DNA, and describe its function in genetic inheritance. Describe the cell cycle and the process of mitosis. Explain the role of mitosis in the formation of new cells, and its importance in maintaining chromosome number during asexual reproduction.

Fun DNA Facts! DNA is too small to see, but under a microscope it looks like a twisted up ladder! (double helix) DNA stands for: D: Deoxyribose N: Nucleic A: Acid Every living thing has DNA. That means that you have something in common with a zebra, a tree, a mushroom and a beetle!!!!

DNA - DEOXYRIBONUCLEIC ACID - blueprint of life (has the instructions for making an organism) - established by James Watson and Francis Crick - codes for your genes - shape of a double helix - made of repeating subunits called nucleotides Gene - a segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color..etc), a gene is a stretch of DNA. Nucleotide - consists of a sugar, phosphate and a base

DNA by the Numbers Each cell has about 2 m of DNA. The average human has 75 trillion cells! If you unravel all the DNA in the chromosomes of one of your cells, it would stretch out 2 meters. If you did this to the DNA in all your cells, it would stretch from here to sun more than 400 hundred times!

DNA is present in the nucleus of all cells in all living organisms DNA controls all the chemical changes which take place in cells The kind of cell which is formed, (muscle, blood, nerve etc) is controlled by DNA

Organization Chromatin = combination of DNA and proteins that make up the contents of the nucleus of a cell. Chromatin condenses into chromosomes

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Review: Prokaryotic & Eukaryotic cells "Prokaryotic" means "before a nucleus," and “Eukaryotic" means "possessing a true nucleus."

Prokaryotic & Eukaryotic cells Eukaryotic cells contain chromosomes Prokaryotic cells contain plasmid DNA and Nucleoid DNA

Prokaryotic cell

Prokaryotic DNA nucleoid - the irregularly-shaped region within a prokaryote cell where the genetic material is localized • plasmid - a circle of double-stranded DNA that is separate from the chromosomes, which is found in bacteria and protozoa

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1953 Watson and Crick determined the structure of DNA

The Shape of the Molecule The basic shape is like a twisted ladder or zipper. This is called a double helix. {Show students a model of the double helix. Explain what a spiral is and a helix is.}

DNA Double Helix “Rungs of ladder” Nitrogenous Base (A,T,G or C) “Legs of ladder” Phosphate & Sugar Backbone

DNA is a very large molecule made up of a long chain of sub-units The sub-units are called nucleotides Each nucleotide is made up of a sugar called deoxyribose a phosphate group and an organic base

Ribose is a sugar, like glucose, but with only five carbon atoms in its molecule Deoxyribose is almost the same but lacks one oxygen atom Both molecules may be represented by the symbol

The bases The organic bases are Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Two Kinds of Bases in DNA Pyrimidines are single ring bases. Purines are double ring bases. N C O C C N C C N

Thymine and Cytosine are pyrimidines Thymine and cytosine each have one ring of carbon and nitrogen atoms. C N O cytosine C N O thymine

Adenine and Guanine are purines Adenine and guanine each have two rings of carbon and nitrogen atoms. C N O Guanine C N Adenine

Hydrogen Bonds The bases attract each other because of hydrogen bonds. Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. The bonds between cytosine and guanine are shown here with dotted lines C N O

Hydrogen Bonds, cont. When making hydrogen bonds, cytosine always pairs up with guanine Adenine always pairs up with thymine Nucleotides pair in a specific way - called the Base-Pair Rule T A G C

Joined nucleotides PO4 sugar-phosphate backbone + bases A molecule of DNA is formed by millions of nucleotides joined together in a long chain

Although each individual repeating unit is very small, DNA polymers can be very large molecules containing millions of nucleotides. For instance, the largest human chromosome, chromosome number 1, is approximately 220 million base pairs long

2-stranded DNA PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4

The bases always pair up in the same way Bonding 1 The bases always pair up in the same way Adenine forms a bond with Thymine Adenine Thymine and Cytosine bonds with Guanine Cytosine Guanine

Bonding 2 PO4 adenine cytosine PO4 thymine PO4 guanine PO4 PO4

Pairing up PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4

THE DOUBLE HELIX bases sugar-phosphate chain

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Attached to each sugar is one of four types of molecules called bases Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four nucleobases along the backbone that encodes information. This information is read using the genetic code. The code is read by copying stretches of DNA into the related nucleic acid RNA in a process called transcription.

Replication The process where DNA makes a copy of itself. During INTERPHASE of Mitosis Why does DNA need to copy? Cells divide for an organism to grow or reproduce Every cell needs a BLUEPRINT of the DNA - DNA replicates right before a cell divides. - Before a cell divides, the DNA strands unwind and separate

DNA replication is semi-conservative DNA replication is semi-conservative. That means that when it makes a copy, one half of the old strand is always kept in the new strand. This helps reduce the number of copy errors

New DNA consists of 1 PARENTAL (original) & 1 NEW strand of DNA Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds Replication Fork Parental DNA Molecule 3’ 5’

To carry the genomic information to daughter cells DNA Duplication Using itself as template

The strands separate PO4 PO4

Each strand builds up its partner by adding the appropriate nucleotides PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 The nucleotides are present in the nucleoplasm. The nuclear equivalent of cytoplasm PO4 PO4 PO4 PO4 PO4

DNA to Protein Genome: the complete set of information in an organism’s DNA Total length of DNA about 2 meters long in a human cell, encoding about 30000 proteins

Human Chromosome: Complex of DNA is called chromatin 44 homologous chromosomes and 2 sex chromosomes Complementary DNA with different Dyes The arrangement of the full chromosome set is called a karyotype

RNA DNA remains in the nucleus, but in order for it to get its instructions translated into proteins, it must send its message to the ribosomes, where proteins are made. The chemical used to carry this message is Messenger RNA RNA = ribonucleic acid. RNA is similar to DNA except: 1. has one strand instead of two strands. 2. has uracil instead of thymine 3. has ribose instead of deoxyribose mRNA has the job of taking the message from the DNA to the nucleus to the ribosomes.

Transcription - RNA is made from DNA Translation - Proteins are made from the message on the RNA

DNA vs. RNA DeoxyriboNucleicAcid vs RiboNucleicAcid A difference between DNA and RNA is the sugar present in the molecules. While the sugar present in an RNA molecule is ribose, the sugar present in a molecule of DNA is deoxyribose. A fifth base, called uracil (U), takes the place of thymine in RNA

DNA vs. RNA DeoxyriboNucleicAcid vs RiboNucleicAcid Transfer the genetic code needed for the creation of proteins from the nucleus to the ribosome. RNA strands are continually made, broken down and reused. Long-term storage and transmission of genetic information DNA is protected in the nucleus, as it is tightly packed.

DNA Damage & Repair Chemicals & ultraviolet radiation damage the DNA in our body cells Cells must continuously repair DAMAGED DNA

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