DNA structure and replication

DNA DISCOVERY STORY DISCOVERY: Rosalind Franklin: Was too nice! She shared her discoveries with Watson and Crick who then were the first to publish and get recognized She confirmed the helical structure, the sugar-phosphate backbone Rosalind Franklin used X-ray diffraction to get information about the structure of DNA. She aimed an X-ray beam at concentrated DNA samples and recorded the scattering pattern of the X-rays on film.

Copyright Pearson Prentice Hall: http://www. biologyjunction The Double Helix  Using clues from Franklin’s pattern, James Watson and Francis Crick built a model that explained how DNA carried information and could be copied. Watson and Crick's model of DNA was a double helix, in which two strands were wound around each other.

DNA: Deoxyribonucleic acid DNA: stores our genetic instructions What is dna? DNA: Deoxyribonucleic acid Deoxyribose: Sugar ( -ose means sugar) DNA: stores our genetic instructions All the information that programs all of our cells activities Code that provides the assembly instructions for everything that lives

Copyright Pearson Prentice Hall: http://www. biologyjunction DNA and Chromosomes Many eukaryotes have 1000 times the amount of DNA as prokaryotes. Eukaryotic DNA is located in the cell nucleus inside chromosomes. The number of chromosomes varies widely from one species to the next.

DNA and Chromosomes Chromosome Structure Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm DNA and Chromosomes Chromosome Structure Eukaryotic chromosomes contain DNA and protein, tightly packed together to form chromatin. Chromatin consists of DNA tightly coiled around proteins called histones. DNA and histone molecules form nucleosomes. Nucleosomes pack together, forming a thick fiber.

Eukaryotic Chromosome Structure Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm DNA and Chromosomes Eukaryotic Chromosome Structure DNA double helix Eukaryotic chromosomes contain DNA wrapped around proteins called histones. The strands of nucleosomes are tightly coiled and supercoiled to form chromosomes.

Cells Somatic Cells: Body cells (any cells that are used in the body besides your sex cells) Replicate with mitosis Mitosis creates two exact copies Interphase, Prophase, Metaphase, Anaphase, Telophase and Cytokinesis

Gametes: Sex cells Cells Replicate with meiosis Meiosis combines genetic material, not an exact copy, creates four cells Two cycles: Interphase I, Prophase I, Metaphase I, Anaphase I, Telophase I and Cytokinesis I Interphase II, Prophase II, Metaphase II, Anaphase II, Telophase II and Cytokinesis II

Humans have 46 chromosomes Chromosomes: arrangements of nucleic acids and proteins that are located in the nucleus of cells and carry genetic information in the form of genes. Genes: unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring Each of the 46 chromosomes contain one DNA molecule packed tightly with proteins in the nucleus

Nucleic acid Nucleic acid: macromolecule (like lipid, proteins, and carbohydrates) Made up of many small repeating units called nucleotides Nucleotides: are made up of: 5-carbon sugar, a phosphate, and 1 of 4 nitrogen bases Nitrogen Bases: Adenine, Cytosine, Thymine, and Guanine

Dna strand 5-carbon sugar 5-carbon sugar Backbones Two different directions one side goes up the other points down Phosphate Phosphate Nitrogen Base's Double Helix

Copyright Pearson Prentice Hall: http://www. biologyjunction DNA is a double helix in which two strands are wound around each other. Each strand is made up of a chain of nucleotides. The two strands are held together by hydrogen bonds between adenine and thymine and between guanine and cytosine.

Nitrogen bases The most significant coding in your DNA comes from these bases They are held together by weak hydrogen bonds They can only be paired with certain bases Adenine Thymine (apples in tree) Cytosine  Guanine (car in garage) This principle is called base pairing.

Decode the matching each of the base pairs Quick check in Decode the matching each of the base pairs AGGTCCG TCCAGGC

RNA RNA: ribonucleic acid, a nucleic acid present in all living cells. Acts as a messenger carrying instructions from DNA for controlling the synthesis of proteins, although in some viruses RNA rather than DNA carries the genetic information

Similarities and differences in dna and rna RNA is a single strand while DNA is the double helix Meaning one back bone Sugar is called ribose and has one more oxygen atom RNA does not contain thymine, instead it has uracil which bonds with adenine Similarities: Both have sugar-phosphate backbone Both have the nucleotides

RNA: is important for producing protein and crucial in replicating DNA RNA’S ROLE RNA: is important for producing protein and crucial in replicating DNA DNA: carries your genetic traits and creates………you

SIMILARITIES AND DIFFERENCES BETWEEN DNA AND RNA

DNA Replication DNA Replication Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm DNA Replication DNA Replication Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing. In most prokaryotes, DNA replication begins at a single point and continues in two directions.

Cells are constantly dividing DNA REPLICATION Cells are constantly dividing Most of them through mitosis (exact copies) This is a benefit as you would not want a skin cell to be created in your blood Every cell in the body has the same DNA It all started with an original and then copies itself trillions of times in your lifetime Each time it replicates itself ½ of the original DNA is used as a template to build a new molecule

DNA replication Helicase: unwinds the double helix, slicing open the loose hydrogen bonds between each of the base pairs

Copyright Pearson Prentice Hall: http://www. biologyjunction DNA Replication In eukaryotic chromosomes, DNA replication occurs at hundreds of places. Replication proceeds in both directions until each chromosome is completely copied. The sites where separation and replication occur are called replication forks.

DNA Replication Duplicating DNA Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm DNA Replication Duplicating DNA  Before a cell divides, it duplicates its DNA in a process called replication. Replication ensures that each resulting cell will have a complete set of DNA.

DNA Replication Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.

DNA Replication How Replication Occurs Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm DNA Replication How Replication Occurs DNA replication is carried out by enzymes that “unzip” a molecule of DNA. Hydrogen bonds between base pairs are broken and the two strands of DNA unwind.

DNA replication Replication Fork: this is the point where splitting stars and creates a leading strand (top) and a lagging strand (bottom)

Dna replication Now the unwound sections can be used as templates to create 2 new complimentary strands in opposite directions

Replicating the leading strand: Dna replication Replicating the leading strand: An enzyme called DNA polymerase is used to add matching nucleotide onto a main stem down the length of the molecule But first it needs a section of nucleotides that fill in the sections that has just been “unzipped”

Dna replication Starting at the beginning of the leading strand DNA polymerase uses a primer to hook onto so it can start building a new DNA chain this is called a RNA primase RNA primase is only used one time and DNA polymerase copies 1st four nucleotides down the chain

DNA Replication New Strand Original strand Nitrogen Bases Growth Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm New Strand Original strand Nitrogen Bases Growth During DNA replication, the DNA molecule produces two new complementary strands. Each strand of the double helix of DNA serves as a template for the new strand. Replication Fork Replication Fork DNA Polymerase

Replication of the lagging strand: DNA REPLICATION Replication of the lagging strand: DNA can copy in one direction Remember the “backbones” are actually in different directions and the lagging strand is backwards

Can only be copied in segments and uses enzyme (RNA primase) DNA REPLICATION Can only be copied in segments and uses enzyme (RNA primase) Can only be used for occasional short RNA primer to give DNA polymerase a starting point to work backwards Strands can only be synthesized in small fragments (Okazaki Fragments)

DNA REPLICATION DNA polymerase has to go back over all the RNA primers and replace them Finally all the fragments join by enzyme DNA Ligase

Copyright Pearson Prentice Hall: http://www. biologyjunction DNA Replication The principal enzyme involved in DNA replication is DNA polymerase. DNA polymerase joins individual nucleotides to produce a DNA molecule and then “proofreads” each new DNA strand.

Types of RNA Types of RNA There are three main types of RNA: Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Types of RNA Types of RNA There are three main types of RNA: messenger RNA ribosomal RNA transfer RNA

Copyright Pearson Prentice Hall: http://www. biologyjunction Types of RNA The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA. Messenger RNA (mRNA) carries copies of instructions for assembling amino acids into proteins.

Copyright Pearson Prentice Hall: http://www. biologyjunction Types of RNA The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA. Ribosomal RNA is combined with proteins to form ribosomes. Ribosomes are made up of proteins and ribosomal RNA (rRNA).

Copyright Pearson Prentice Hall: http://www. biologyjunction Types of RNA Amino acid The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA. Transfer RNA During protein construction, transfer RNA (tRNA) transfers each amino acid to the ribosome.

DNA molecule DNA strand (template) 3¢ 5¢ TRANSCRIPTION mRNA 5¢ 3¢ Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm DNA molecule DNA strand (template) 3¢ 5¢ TRANSCRIPTION mRNA 5¢ 3¢ Codon TRANSLATION Protein Amino acid

Transcription DNA is copied in the form of RNA This first process is called transcription. The process begins at a section of DNA called a promoter. Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm

Copyright Pearson Prentice Hall: http://www. biologyjunction During transcription, RNA polymerase uses one strand of DNA as a template to assemble nucleotides into a strand of RNA. Transcription

Copyright Pearson Prentice Hall: http://www. biologyjunction RNA Editing Some DNA within a gene is not needed to produce a protein. These areas are called introns. The DNA sequences that code for proteins are called exons. RNA Editing

The introns are cut out of RNA molecules. Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm RNA Editing The introns are cut out of RNA molecules. The exons are the spliced together to form mRNA. Exon Intron DNA Pre-mRNA mRNA Many RNA molecules have sections, called introns, edited out of them before they become functional. The remaining pieces, called exons, are spliced together. Then, a cap and tail are added to form the final RNA molecule. Cap Tail

Copyright Pearson Prentice Hall: http://www. biologyjunction The Genetic Code The Genetic Code The genetic code is the “language” of mRNA instructions. The code is written using four “letters” (the bases: A, U, C, and G).

Copyright Pearson Prentice Hall: http://www. biologyjunction The Genetic Code A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid. A codon is a group of three nucleotides on messenger RNA that specify a particular amino acid.

Copyright Pearson Prentice Hall: http://www. biologyjunction The Genetic Code The genetic code shows the amino acid to which each of the 64 possible codons corresponds. To decode a codon, start at the middle of the circle and move outward.

Translation Translation Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Translation Translation is the decoding of an mRNA message into a polypeptide chain (protein). Translation takes place on ribosomes. During translation, the cell uses information from messenger RNA to produce proteins.

Copyright Pearson Prentice Hall: http://www. biologyjunction Translation The ribosome binds new tRNA molecules and amino acids as it moves along the mRNA. Phenylalanine tRNA Ribosome During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process. mRNA Start codon

Lysine tRNA Translation direction Protein Synthesis Translation mRNA Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Lysine tRNA Protein Synthesis During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process. Translation direction mRNA Ribosome

The process continues until the ribosome reaches a stop codon. Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Translation The process continues until the ribosome reaches a stop codon. Polypeptide Ribosome tRNA During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process. mRNA

Amino acids within a polypeptide Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Codon Codon Codon GENES AND PROTIEN DNA mRNA Protein Single strand of DNA Codon Codon Codon mRNA This diagram illustrates how information for specifying the traits of an organism is carried in DNA. The sequence of bases in DNA is used as a template for mRNA. The codons of mRNA specify the sequence of amino acids in a protein, and proteins play a key role in producing an organism’s traits. Alanine Arginine Leucine Amino acids within a polypeptide

12–4 Mutations 12-4 Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm 12–4 Mutations

Mutations are changes in the genetic material. Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Mutations are changes in the genetic material. Kinds of Mutations Mutations that produce changes in a single gene are known as gene mutations. Mutations that produce changes in whole chromosomes are known as chromosomal mutations.

Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Gene Mutations  Gene mutations involving a change in one or a few nucleotides are known as point mutations because they occur at a single point in the DNA sequence. Point mutations include substitutions, insertions, and deletions.

Substitutions usually affect no more than a single amino acid. Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Substitutions usually affect no more than a single amino acid. Gene mutations result from changes in a single gene. In a substitution, one base replaces another.

The effects of insertions or deletions are more dramatic. Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm The effects of insertions or deletions are more dramatic. The addition or deletion of a nucleotide causes a shift in the grouping of codons. Changes like these are called frameshift mutations.

In an insertion, an extra base is inserted into a base sequence. Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm In an insertion, an extra base is inserted into a base sequence. Gene mutations result from changes in a single gene. In an insertion, an extra base is inserted into a base sequence.

Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm In a deletion, the loss of a single base is deleted and the reading frame is shifted. Gene mutations result from changes in a single gene. The loss of a single letter in a sentence models the effects of the deletion of one base in a DNA sequence.

Chromosomal Mutations Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Chromosomal Mutations  Chromosomal mutations involve changes in the number or structure of chromosomes. Chromosomal mutations include deletions, duplications, inversions, and translocations.

Deletions involve the loss of all or part of a chromosome. Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Deletions involve the loss of all or part of a chromosome. Chromosomal mutations involve changes in whole chromosomes.

Copyright Pearson Prentice Hall: http://www. biologyjunction Kinds of Mutations Duplications produce extra copies of parts of a chromosome. Chromosomal mutations involve changes in whole chromosomes.

Inversions reverse the direction of parts of chromosomes. Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Inversions reverse the direction of parts of chromosomes. Chromosomal mutations involve changes in whole chromosomes.

Kinds of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Translocations occurs when part of one chromosome breaks off and attaches to another. Chromosomal mutations involve changes in whole chromosomes.

Significance of Mutations Copyright Pearson Prentice Hall: http://www.biologyjunction.com/powerpoints_dragonfly_book_prent.htm Significance of Mutations Many mutations have little or no effect on gene expression. Some mutations are the cause of genetic disorders. Polyploidy is the condition in which an organism has extra sets of chromosomes.