Chapter 5 Lesson 3Chapter 5 Lesson 3

DNA and GeneticsDNA and Genetics

The Discovery of the Structure of DNA

James Watson and Fransis CrickRosalind Franklin

DNA Structure

• DNA looks like a twisted ladder and is often called a ________________.double helix

DNA Structurea. The sides of the ladder are made up of molecules

of ______________ called ______________ that are alternating with molecules of phosphate.

sugar deoxyribose

DNA StructureDNA Structure

• Ladder rungs are made up of a pair of Ladder rungs are made up of a pair of molecules called nitrogen bases molecules called nitrogen bases (containing nitrogen and other (containing nitrogen and other elements). The four nitrogen bases are:elements). The four nitrogen bases are:

o ____________________(A)____________________(A)o ____________________(T)____________________(T)o ____________________(G)____________________(G)o ____________________(C)____________________(C)

Adenine

Thymine

Guanine

Cytosine

DNA Structure

• How do the nitrogen bases pair up to make the rungs of the DNA ladder?

o ______________ pairs only with _______________

o ______________ pairs only with _______________

Adenine Thymine

Cytosine Guanine

Nitrogen Base Pairing

What is DNA Replication?What is DNA Replication?

The process of copying a DNA The process of copying a DNA molecule to make another DNA molecule to make another DNA molecule that is an exact copy.molecule that is an exact copy.

DNA ReplicationDNA Replication• DNA molecule unwinds and separates DNA molecule unwinds and separates

between the nitrogen bases on each between the nitrogen bases on each rung.rung.

• ____________________ that are floating in ____________________ that are floating in the nucleus pair up with each half (A the nucleus pair up with each half (A with T and G with C)with T and G with C)

• Two identical DNA molecules are formedTwo identical DNA molecules are formed• The order of nitrogen bases in each new The order of nitrogen bases in each new

DNA molecule will exactly match the DNA molecule will exactly match the order in the original DNA molecule.order in the original DNA molecule.

Nucleotides

DNA Replication• DNA replication ensures that:

• each new daughter cell will have a complete set of DNA which it needs to carry out all the cell’s activities.

DNA ReplicationDNA Replication

http://www.youtube.com/watch?v=hfZ8o9D1tus

Let’s Review DNALet’s Review DNA

What are the 4 different nitrogen bases What are the 4 different nitrogen bases in a DNA molecule? How do they pair?in a DNA molecule? How do they pair? Adenine pairs with ThymineAdenine pairs with Thymine Cytosine pairs with GuanineCytosine pairs with Guanine

Base Pairing – The secret to the Base Pairing – The secret to the code!!code!!

Adenine pairs with Thymine

Guanine pairs with Cytosine

Introducing a New PlayerIntroducing a New Player

This structure, along with DNA, is This structure, along with DNA, is critical in the construction of YOU!critical in the construction of YOU!

This structure comes in three different This structure comes in three different forms with different functions.forms with different functions.

What is the name of this “New Player”?What is the name of this “New Player”?

RNARNA

DNA vs. RNA – DNA vs. RNA – How are they different?How are they different?

DNA vs. mRNADNA vs. mRNA How many strands in each? How many strands in each? (ex. How many (ex. How many

sides?)sides?)

DNA – Double strandDNA – Double strand RNA – Single strandRNA – Single strand

DNA vs. mRNADNA vs. mRNA What are the nitrogen bases in each?What are the nitrogen bases in each?

DNA – has A, T, C, GDNA – has A, T, C, G RNA – has A, U, C, GRNA – has A, U, C, G

DNA vs. mRNADNA vs. mRNA What is the sugar in each backbone?What is the sugar in each backbone?

DNA – has deoxyriboseDNA – has deoxyribose RNA – has riboseRNA – has ribose

Three types of RNAThree types of RNA

mRNA (messenger RNA)mRNA (messenger RNA)

tRNA (transfer RNA)tRNA (transfer RNA)

rRNA (ribosomal RNA)rRNA (ribosomal RNA)

The Genetic CodeThe Genetic Code

Genes make proteins Proteins make YOU!!

ATTCGGTG

Protein StructureProtein Structure

unwind

Your DNA determines the proteins that are produced. These proteins give you your traits such as hair color, eye color, and skin color.

The Genetic Code (cont.)The Genetic Code (cont.)

What are the building blocks of What are the building blocks of protein? protein?

A group of three nitrogen A group of three nitrogen bases codes for a specific bases codes for a specific amino acid.amino acid.

The production of proteins is The production of proteins is called protein synthesis.called protein synthesis. Two steps – Transcription and Two steps – Transcription and

TranslationTranslation

The Genetic CodeThe Genetic Code The order of nitrogen bases along a gene The order of nitrogen bases along a gene

forms a forms a Genetic CodeGenetic Code that specifies what that specifies what type of protein will be type of protein will be producedproduced..

The type of protein produced determines The type of protein produced determines the trait!the trait!

Are you ready to see the code that Are you ready to see the code that unlocks the mystery of life????unlocks the mystery of life????

Are you sure?????Are you sure????? Are you really sure????Are you really sure????

The Genetic CodeThe Genetic Code

Protein synthesis takes place on the Protein synthesis takes place on the ribosome.ribosome.

Two types of RNATwo types of RNA

A Look at Protein Synthesis:A Look at Protein Synthesis:

Protein SynthesisProtein Synthesis

http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter3/animation__how_translation_works.html

Steps of Protein SynthesisSteps of Protein SynthesisFig. 15 – pg. 173Fig. 15 – pg. 173

DNA “unzips” between the Nitrogen DNA “unzips” between the Nitrogen Base pairsBase pairs

mRNA nucleotides pair up with DNA mRNA nucleotides pair up with DNA nucleotidesnucleotides

Completed mRNA moves into the Completed mRNA moves into the cytoplasmcytoplasm

This process is called TRANSCRIPTIONThis process is called TRANSCRIPTION

Steps of Protein Synthesis Steps of Protein Synthesis (cont.)(cont.)

Fig. 15 – pg. 173Fig. 15 – pg. 173 The genetic messenger is called The genetic messenger is called

messenger RNA (or mRNA).messenger RNA (or mRNA). mRNA carries the DNA code from the mRNA carries the DNA code from the

nucleus out into the cell’s cytoplasm to nucleus out into the cell’s cytoplasm to the ribosomes where proteins are the ribosomes where proteins are produced.produced.

Why can’t DNA deliver the code to the Why can’t DNA deliver the code to the ribosomes?ribosomes? DNA is too large to fit through the nuclear pores.DNA is too large to fit through the nuclear pores.

Steps of Protein Synthesis Steps of Protein Synthesis (cont.)(cont.)

Fig. 16 – pg. 174Fig. 16 – pg. 174 Transfer RNA (tRNA) carries amino acids to Transfer RNA (tRNA) carries amino acids to

the ribosome.the ribosome. tRNA matches up to mRNA using base tRNA matches up to mRNA using base

pairing rules: A-U and C-Gpairing rules: A-U and C-G Each tRNA molecule attaches the amino Each tRNA molecule attaches the amino

acid to the growing protein chain.acid to the growing protein chain.

This process is called TRANSLATION This process is called TRANSLATION (nucleic (nucleic acid language is “translated” to amino acid acid language is “translated” to amino acid language – a protein is made from mRNA)language – a protein is made from mRNA)

A review of your notes:A review of your notes:

What is a codon?What is a codon? Series of three nitrogen bases on mRNASeries of three nitrogen bases on mRNA

How many codons are possible?How many codons are possible? 64 codons64 codons

How many different amino acids are How many different amino acids are there?there? 20 different amino acids to form proteins20 different amino acids to form proteins

Let’s Review Protein Synthesis:Let’s Review Protein Synthesis:

MutationMutation

Definition – a change in the Definition – a change in the nucleotide sequence of a gene. This nucleotide sequence of a gene. This causes the cell to produce an causes the cell to produce an incorrect protein which results in a incorrect protein which results in a different physical trait or phenotype.different physical trait or phenotype.

Mutations Mutations (pg. 175, Figure 17)(pg. 175, Figure 17)

Substitution Mutation

Deletion Mutation

Insertion Mutation

The mice ran away.

The rice ran away.

Thei cera naway.

The migukce ran away.

MutationsMutations

Mutations are usually random and Mutations are usually random and can be:can be: Harmful – causes harm to the organismHarmful – causes harm to the organism Helpful – helps the organism to surviveHelpful – helps the organism to survive Neither harmful or helpful.Neither harmful or helpful.

Mutations can also be caused by Mutations can also be caused by environmental hazards.environmental hazards. These are usually harmfulThese are usually harmful

CancerCancer• Cancer is a disease in which:Cancer is a disease in which:

• Cells grow and divide uncontrollably, Cells grow and divide uncontrollably, damaging the parts of the body around damaging the parts of the body around them.them.

• Cancer can occur when something Cancer can occur when something damages a portion of DNA in a damages a portion of DNA in a chromosome. This damage causes a chromosome. This damage causes a change in DNA called _____________.change in DNA called _____________.

mutation

CancerCancer• Abnormal cells that develop Abnormal cells that develop

uncontrollably may form a mass of uncontrollably may form a mass of abnormal cells which is called a abnormal cells which is called a _________________._________________.

• Treatment for cancer include Treatment for cancer include _____________, ________________ and or _____________, ________________ and or ________________________________________

tumor

surgery radiation

Drugs (chemotherapy)

QuestionsQuestions

Why can’t DNA leave the nucleus to Why can’t DNA leave the nucleus to produce proteins?produce proteins?

Why is it important for meiosis to Why is it important for meiosis to occur? What would happen if human occur? What would happen if human sex cells had 46 chromosomes sex cells had 46 chromosomes instead of 23?instead of 23?

Human CellsHuman Cells Human body cells contain 46 chromosomes Human body cells contain 46 chromosomes

(23 pairs)(23 pairs) Sex cells (egg and sperm) contain 23 Sex cells (egg and sperm) contain 23

chromosomeschromosomes The 23The 23rdrd pair of chromosomes determines the sex pair of chromosomes determines the sex

of an individual.of an individual. Female genotype – XXFemale genotype – XX Male genotype – XYMale genotype – XY

Design a Punnett Square to calculate the Design a Punnett Square to calculate the probability of a man and woman having a baby girl probability of a man and woman having a baby girl of baby boyof baby boy

KaryotypeKaryotype Definition – Definition –

picture of all the picture of all the chromosomes in chromosomes in a cell arranged a cell arranged in pairsin pairs

Is this Is this karyotype from karyotype from a male or a male or female?female?

Where is there a problem?Where is there a problem?