UNIT IV

Chapter 12 DNA and RNA

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. 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 lipids, carbohydrates, and other molecules- transformation still occurred.

c. Repeated using enzymes that would break down DNA (protein). 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 (side of ladder)2). Phosphate group (side of ladder)

3). Nitrogenous (nitrogen containing) base (1/2 rung of ladder)

a). Four kinds of nitrogenous bases

b). Purines- include adenine and guanine

c). Pyrimidines- include cytosine and thymine

b. Backbone (side of ladder) 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 used X-ray diffraction to study structure of DNA molecule. Concluded structure was coiled like a spring (helix)

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

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 in this bacterium is about 1000 times as long as the bacterium itself. It must therefore by very tightly folded

2. Eukaryotic Cells- DNA located in cells 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 tightly packed together to form substance called chromatinchromatin. DNA coiled around proteins called histones histones (glue)(glue)

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 replicationreplication

a. DNA molecule separates into two strands

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

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

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 stranded (half of ladder)single stranded (half of ladder)

c. RNA contains uraciluracil in place of thymine

2. Most RNA involved in Protein SynthesisProtein Synthesis3. 3 Types of RNA3 Types of RNA

a. Messenger RNAMessenger RNA (mRNAmRNA)- disposable complementary strand of DNA to carry instructions to tRNA on ribosomesb. Ribosomal RNARibosomal RNA (rRNArRNA)- helps to assemble tRNA on ribosomesc. Transfer RNATransfer RNA (tRNAtRNA)- transfers amino acids to ribosomes to construct protein molecules

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

1. Enzyme (RNA Polymerase) separates DNA strand2. One strand of DNA used as template to assemble strand of mRNA. Takes place in nucleus

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

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” (A, G, U, C) * no T in RNA*

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

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

f. Protein and mRNA released completing process of translation

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

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- most involve a mistake in only one nucleotide

2. Point mutationsPoint mutations- occurs at a single point in DNA sequence. Generally changes only one amino acid

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

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

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

C. Gene RegulationGene Regulation- how does organism “know” when to turn a gene on or off?

1. Genes are “turned off” by presence of a repressor proteinrepressor protein (produced by regulator gene)

3. Presence of certain chemicals (e.g.- lactose in E. ecoli ) bind to site on repressor protein causing it to change shape and “fall off” the DNA molecule.

4. RNA plymerase is allowed to transcribe mRNA molecule to code for protein (e.g. enzymes to break apart lactose molecules)

D. Regulation and Development- especially important in shaping the way a complex organism develops from single fertilized cell.

1. Hox genesHox genes- controls organs and tissues that develop in various parts of the embryo

a. Mutation in one of these “master control genes” can completely change organs that develop in specific parts of the body

b. Genes tell cells in the body which organs and structures they should develop into as the body grows.

2. Mutations may have led to drastic and quick evolutionary changes

Mutations affecting the hox genes in the fruit fly, Drosophila, for example, can replace the fly’s antennae with a pair of legs growing right out of its head!

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

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. mRNA molecules

b. DNA molecules

c. RNA polymerase

d. proteins

What is produced during transcription?

a. mRNA molecules

b. DNA molecules

c. RNA polymerase

d. proteins

What does the figure below show?

a. mRNA codons

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. mRNA codons

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 makes 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 makes 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.

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

bacteriophage

Mutations seen below are caused by genes known as _____ genes.

hox

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 diagramed below?

transcription

What is this structure?

Nuclear envelope

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

Point mutation