DNA R37

DNA R37

Who really discovered DNA?

Who played a major role?

• Linus Pauling– Developed the triple strand structure

• Rosalind Franklin & Maurice Wilkins– X-ray diffraction, crystalline structure, and

equidistance between bases

• Erwin Chargaff– Chargaff’s Ratio

DNA and RNA

I. DNA- deoxyribonucleic acid

A. History of DNA as Genetic Material “code of life”

1. Griffith and Transformation

a. Frederick Griffith made discovery while investigating bacteria known to produce pneumonia

b. Griffith isolated two different strains of bacteria

1). Disease causing strain- had smooth edges. When injected into mice caused pneumonia.

2). Harmless strain- grew with rough edges.

c. When disease causing bacteria heated- mice survived when injected

d. Mixed the heated-killed bacteria and harmless ones. When injected caused pneumonia. Concluded that one strain had been changed into another. Called transformation.

2. (Oswald) Avery and DNA- group of scientists repeated Griffith’s experiment to discover “transforming” factor.

a. Made extract from heat-killed bacteria

b. Treated extract with enzymes that destroyed proteins, lipids, carbohydrates, and other molecules- transformation still occurred.c. Repeated using enzymes that would break down DNA. Transformation did not occur!d. Concluded- DNA carries genetic code

3. Hershey-Chase Experiment- (1952) showed conclusively that DNA was molecule that carried genetic code

a. Studied viruses known as bacteriophages

b. Used different radioactive markers to label DNA and proteins of bacteriophages

B. The Structure of DNA

1. DNA made of units called nucleotides

a. Nucleotides made up of 3 parts

1). 5-carbon sugar called deoxyribose

2). Phosphate group

3). Nitrogenous (nitrogen containing) base

a). Four kinds of nitrogenous bases

b). Purines- include adenine and guanine

c). pyrimidines- include cytosine and thymine

b. Backbone of DNA chain formed by sugar and phosphate groups of nucleotides

sugar

phosphate

2. Discoveries- understanding DNA’s structure

a. Chargaff’s Rule- ratio of guanine:cytosine and adenine:thymine are equal

A = T and G = C

b. X-Ray evidence- 1950’s Rosalind Franklin and Maurice Wilkins used X-ray diffraction to study structure of DNA molecule. Concluded structure was coiled like a spring (helix)

http://it.wikipedia.org/wiki/Immagine:Rosalind_Franklin.jpg

c. The Double Helix- after looking at Franklin and Wilkin’s work, Watson and Crick constructed a model of DNA molecule (1953)

1). Hydrogen bonds between base pairs holds two strands together

2). Base Pairing –explained Chargaff’s Rule A=T and C=G

• In 1962, Watson, Crick and Wilkins received the Nobel Prize in medicine for their work on DNA

• Rosalind Franklin had died in 1958 from cancer (most likely caused by working with X-rays) and was not recognized

Complementary Base Pairs

• What would the complementary strand look like for the following:

• ATGCGGTCCCGAATA

TACGCCAGGGCTTAT

• CGAGCTTCTAGATCT

GCTCGAAGATCTAGA

DNA Replication R39

II. Chromosomes and DNA ReplicationChromosomes and DNA Replication

A. DNA and Chromosomes- found in both eukaryotic and prokaryotic cells

1. Prokaryotic cells- DNA located in cytoplasm in single circular DNA molecule (referred to as cell’s chromosome)

The DNA is a bacterium is about 1000 times as long as the bacterium itself. It must therefore by very tightly folded

2. Eukaryotic Cells- DNA located in cell’s nucleus in form of a number of chromosomes

B. Chromosome Structure- even the smallest of human chromosomes contains 30 million base pairs

1. Eukaryotic chromosomes are tightly packed together; formed from the substance called chromatinchromatin. DNA coiled around proteins called histoneshistones

2. NucleosomeNucleosome- DNA wrapped around histones

C. DNA ReplicationDNA Replication

1. Duplicating DNA- before cell divides, it duplicates it’s DNA in a process called replication

a. First, DNA molecule’s hydrogen bonds break and the DNA separates into two strands (helicase enzymes)

b. Two new complementary strands are produced (base pairing) each strand serves as template for new strand

c. Process carried out by series of enzymes (DNA polymerase)

5’ vs. 3’

• 5’ end– Phosphate

• 3’ end– OH-

• Read from 3’ to 5’

• Synthesized from 5’ to 3’

DNA Interactive

• www.dnai.org

• “Copying the Code”

• “Putting it Together”-Replication

• Watch the Videos & do the Activity

http://www.dnai.org/

• DNA PRACTICE WORKSHEET

GENES AND RNA R40

• Nucleotides in DNA are grouped into genes, which contain the information required for the production of specific proteins

One gene, one polypeptide

• George Beadle & Edward Tatum– Orange bread mold (Neurospora

crassa)– “One gene-one enzyme”

hypothesis

• Genes actually dictate the production of a single polypeptide (part that makes up a protein/enzyme).– One gene-one polypeptide

D. RNA and Protein SynthesisRNA and Protein Synthesis

1. Structure of RNA- 3 main differences between RNA and DNA

a. Sugar in RNA is riboseribose

b. RNA is single strandedsingle stranded

c. RNA contains uraciluracil in place of thyminethymine

2. Most RNA involved in Protein SynthesisProtein Synthesis3. 3 Types of RNA3 Types of RNAa. Messenger RNAMessenger RNA (mRNAmRNA)- disposable copy of DNAto carry instructions to rest of cellb. Ribosomal RNARibosomal RNA (rRNArRNA)- helps to assemble proteins on ribosomes. c. Transfer RNATransfer RNA (tRNAtRNA)- transfers amino acids to ribosomes to construct protein molecules

4. Ribosomes are the factories where proteins are made.

E. TranscriptionTranscription- process by which DNA makes complementary sequence of RNA

1. Enzyme (RNA Polymerase) separates DNA strand2. One strand of DNA is used as template to assemble a strand of RNA. This takes place in nucleus

3. Transcription begins at specific locations on DNA (promoters)

DNA Interactive

• www.dnai.org


• “Putting it Together”-Transcription



Protein Synthesis R41

F. TranslationsTranslations- “making Proteins” Translating language of nucleic acids (base sequences) into language of proteins (amino acids)

1. Gene carries code to make one protein (300 to 3000 base pairs)

a. Code written in language with only 4 “letters”

b. Code read 3 letters at a time (each 3 letter “word” known as a codoncodon

UCGCACGGUUCG – CAC – GGU

Represents the amino acidsSerine – Histidine – Glycine

Triplet Code

Figure 11-13

Each codon stands for a particular amino acid.

The codon AUG not only stands for methionine (Met), but also functions as a signal to "start" translating an RNA transcript.

There are also three "stop" codons that do not code for amino acids, but signal the end of each genetic message.

2. Process used all 3 types of RNA

a. mRNA transcribed in nucleus and released into the cytoplasm

b. mRNA attaches to ribosome. Translation begins AUGAUG, the start codon start codon

c. Each tRNA has an anticodonanticodon whose bases are complementary to codoncodon on mRNA. tRNA brings amino acids to ribosomes

anticodonanticodon

codoncodon

d. Ribosome moves along mRNA, binding new tRNA molecules and amino acids

e. Polypeptide chain (protein) grows until ribosome reaches stop codonstop codon

stop codonstop codon

Protein moleculeProtein molecule

Information Flow: DNA to RNA to Protein

f. Protein and mRNA released completing process of translation

DNA Interactive

• www.dnai.org





DNA Interactive

• www.dnai.org

• “Reading the Code”


• Watch Video & do the Interactive Activity


GGCUACCCCGCUUAG

Gly – Tyr – Pro – Ala - STOP

UCGACCUGCCUAUAG

Ser – Thr – Cys – Leu - STOP

GUGACCGUACAUUAG

Val – Thr – Val – His - STOP

GGGAAAUUUCCCUAG

Gly – Lys – Phe – Pro - STOP

Mutations R42

G. Genes and Proteins- proteins are key to everything cells do. FunctionalFunctional (enzymes) and structural proteinsstructural proteins

Figure 11-20There are two general categories of gene mutation: base substitution and base insertion (or deletion). The effect on the resulting polypeptide is shown here, following substitution (a) and deletion (b).

III. MutationsMutations- - changes in the DNA sequence that affect genetic information

A. Gene MutationsGene Mutations- results from changes in a single gene

1. Several types- some involve several nucleotides, but most affect only one

2. Point mutationsPoint mutations- occurs at a single point in DNA sequence. Generally change in one of amino acids

• Point Mutation – This is equivalent to changing one letter in a

sentence, such as this example, where we change the 'c' in cat to an 'h':

Original The fat cat ate the wee rat.

Pt Mutation The fat hat ate the wee rat.

b. Can alter protein- making it unable to perform normal functions

a. Frameshift mutationFrameshift mutation- insertion or deletion of nucleotide. Causes bigger changes!

c. But because our cells read DNA in three letter words, adding or removing one letter changes each subsequent word. This type of mutation can make the DNA meaningless and often results in a shortened protein.

Types of Mutations

• Frame-shift mutation

– An example of a frame-shift mutation using our sample sentence is when the 't' from cat is removed, but we keep the original letter spacing:

Original The fat cat ate the wee rat.Frame Shift The fat caa tet hew eer at.

B. Chromosomal MutationsChromosomal Mutations- involves changes in the number and structure of chromosomes

Types of Mutations• Deletion

– Mutations that result in missing DNA are called deletions.

– These can be small, such as the removal of just one "word," or longer deletions that affect a large number of genes on the chromosome.

– Deletions can also cause frameshift mutations.

– In this example, the deletion eliminated the word cat.


Deletion The fat ate the wee rat.

Types of Mutations• Insertion

– Mutations that result in the addition of extra DNA are called insertions.

– Insertions can also cause frameshift mutations, and general result in a nonfunctional protein.


Insertion The fat cat xlw ate the wee rat.

Types of Mutations• Inversion

– In an inversion mutation, an entire section of DNA is reversed.

– A small inversion may involve only a few bases within a gene, while longer inversions involve large regions of a chromosome containing several genes.


Inversion The fat tar eew eht eta tac.

What Causes Mutations?

• Mutations may occur when errors are made during DNA replication, or when errors are made during chromosome crossovers in meiosis.

• Physical or chemical agents that cause mutations are called mutagens.

Mutagens• The most common physical mutagen is high-energy

radiation, such as X-rays and ultraviolet light. One type of chemical mutagen consists of chemicals that are similar to normal DNA bases but cause incorrect base-pairing when incorporated into DNA.

• If a mutation is present in an organism's gametes, it can be passed on to its offspring.

Advantages to Mutations

• Although mutations are often harmful, they can alter a protein in a way that may be beneficial in certain environments.

• For example, a genetic mutation is responsible for the dark color seen in some females of the tiger swallowtail butterfly species, Papilio glaucus.

• The mutation may be advantageous when the environment includes a related species, the poisonous black swallowtail Battus philenor. Predators that avoid eating the black swallowtail may also avoid eating its mimic, the dark form of Papilio glaucus.

Chapter 12 DNA and RNA

The figure below shows the structure of a(an)

a. DNA molecule.

b. amino acid.

c. RNA molecule.

d. protein.

The figure below shows the structure of a(an)

a. DNA molecule.

b. amino acid.

c. RNA molecule.

d. protein.

Identify structure outlined and labeled by the letter X in Figure below.

a. RNA

b. Phosphate

c. Nucleotide

d. 5-carbon sugar

Identify structure outlined and labeled by the letter X in Figure below.

a. RNA

b. Phosphate

c. Nucleotide

d. 5-carbon sugar

Albinism is an autosomal recessive trait. What is the only way in which an individual can become an albino?

Which of the following is a nucleotide found in DNA?

a. ribose + phosphate group + thymine

b. ribose + phosphate group + uracil

c. deoxyribose + phosphate group + uracil

d. deoxyribose + phosphate group + cytosine

Which of the following is a nucleotide found in DNA?

a. ribose + phosphate group + thymine

b. ribose + phosphate group + uracil

c. deoxyribose + phosphate group + uracil

d. deoxyribose + phosphate group + cytosine

Because of base pairing in DNA, the percentage of

a. adenine molecules in DNA is about equal to the percentage of guanine molecules.

b. pyrimidines in DNA is about equal to the percentage of purines.

c. purines in DNA is much greater than the percentage of pyrimidines.

d. cytosine molecules in DNA is much greater than the percentage of guanine molecules.

Because of base pairing in DNA, the percentage of

a. adenine molecules in DNA is about equal to the percentage of guanine molecules.

b. pyrimidines in DNA is about equal to the percentage of purines.

c. purines in DNA is much greater than the percentage of pyrimidines.

d. cytosine molecules in DNA is much greater than the percentage of guanine molecules.

DNA is copied during a process called

a. replication.

b. translation.

c. transcription.

d. transformation.

DNA is copied during a process called

a. replication.

b. translation.

c. transcription.

d. transformation.

DNA replication results in two DNA molecules,

a. each with two new strands.

b. one with two new strands and the other with two original strands.

c. each with one new strand and one original strand.

d. each with two original strands.

DNA replication results in two DNA molecules,

a. each with two new strands.

b. one with two new strands and the other with two original strands.

c. each with one new strand and one original strand.

d. each with two original strands.

During DNA replication, a DNA strand that has the bases CTAGGT produces a strand with the bases

a. TCGAAC.

b. GATCCA.

c. AGCTTG.

d. GAUCCA.

During DNA replication, a DNA strand that has the bases CTAGGT produces a strand with the bases

a. TCGAAC.

b. GATCCA.

c. AGCTTG.

d. GAUCCA.

In eukaryotes, DNA

a. is located in the nucleus.

b. floats freely in the cytoplasm.

c. is located in the ribosomes.

d. is circular.

In eukaryotes, DNA

a. is located in the nucleus.

b. floats freely in the cytoplasm.

c. is located in the ribosomes.

d. is circular.

RNA contains the sugar

a. ribose.

b. deoxyribose.

c. glucose.

d. lactose.

RNA contains the sugar

a. ribose.

b. deoxyribose.

c. glucose.

d. lactose.

Unlike DNA, RNA contains

a. adenine.

b. uracil.

c. phosphate groups.

d. thymine.

Unlike DNA, RNA contains

a. adenine.

b. uracil.

c. phosphate groups.

d. thymine.

Which of the following are found in both DNA and RNA?

a. ribose, phosphate groups, and adenine

b. deoxyribose, phosphate groups, and guanine

c. phosphate groups, guanine, and cytosine

d. phosphate groups, guanine, and thymine

Which of the following are found in both DNA and RNA?

a. ribose, phosphate groups, and adenine

b. deoxyribose, phosphate groups, and guanine

c. phosphate groups, guanine, and cytosine

d. phosphate groups, guanine, and thymine

How many main types of RNA are there?

a. 1

b. 3

c. hundreds

d. thousands

How many main types of RNA are there?

a. 1

b. 3

c. hundreds

d. thousands

Which type(s) of RNA is(are) involved in protein synthesis?

a. transfer RNA only

b. messenger RNA only

c. ribosomal RNA and transfer RNA only

d. messenger RNA, ribosomal RNA, and transfer RNA

Which type(s) of RNA is(are) involved in protein synthesis?

a. transfer RNA only

b. messenger RNA only

c. ribosomal RNA and transfer RNA only

d. messenger RNA, ribosomal RNA, and transfer RNA

What is produced during transcription?

a. RNA molecules

b. DNA molecules

c. RNA polymerase

d. proteins

What is produced during transcription?

a. RNA molecules

b. DNA molecules

c. RNA polymerase

d. proteins

What does the figure below show?

a. anticodons

b. the order in which amino acids are linked

c. the code for splicing mRNA

d. the genetic code

What does the figure below show?

a. anticodons

b. the order in which amino acids are linked

c. the code for splicing mRNA

d. the genetic code

How many codons are needed to specify three amino acids?

a. 3

b. 6

c. 9

d. 12

How many codons are needed to specify three amino acids?

a. 3

b. 6

c. 9

d. 12

What happens during the process of translation?

a. Messenger RNA is made from DNA.

b. The cell uses information from messenger RNA to produce proteins.

c. Transfer RNA is made from messenger RNA.

d. Copies of DNA molecules are made.

What happens during the process of translation?

a. Messenger RNA is made from DNA.

b. The cell uses information from messenger RNA to produce proteins.

c. Transfer RNA is made from messenger RNA.

d. Copies of DNA molecules are made.

Genes contain instructions for assembling

a. purines.

b. nucleosomes.

c. proteins.

d. pyrimidines.

Genes contain instructions for assembling

a. purines.

b. nucleosomes.

c. proteins.

d. pyrimidines.

Which type of RNA functions as a blueprint of the genetic code?

a. rRNA

b. tRNA

c. mRNA

d. RNA polymerase

Which type of RNA functions as a blueprint of the genetic code?

a. rRNA

b. tRNA

c. mRNA

d. RNA polymerase

A mutation that involves a single nucleotide is called a(an)

a. chromosomal mutation.

b. inversion.

c. point mutation.

d. translocation.

A mutation that involves a single nucleotide is called a(an)

a. chromosomal mutation.

b. inversion.

c. point mutation.

d. translocation.

Completion:

The Watson and Crick model of DNA is a(an) __________ ____________, in which two strands are wound around each other.

Double Helix

Completion:

The figure below shows three types of ____________.

RNA molecules

Completion:

During transcription, the ___________________ between base pairs are broken.

Hydrogen bonds

Completion:

The order of nitrogenous bases in DNA determines the order of ____________________ in proteins.

Amino acids

Completion:

The ____________________ of a tRNA molecule determines the type of amino acid that bonds with the tRNA.

anticodon

What is the name of the yellow structure that is “landing” onto the blue structure?

bacteriophage

What process is taking place below?

Translation

These scientists discovered the structure of a DNA molecule. Who are they?

Watson and Crick

Which type of RNA below is involved with the process of translation?

All three

What process is diagrammed below?

transcription

What is this structure?

Nuclear envelope

Sickle cell anemia is caused by what type of genetic mutation?

Point mutation

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DNA R37