Ch 9

To fulfill its role, the genetic material must meet several criteria

1. _______: It must contain the ______ (same word) necessary to make an entire organism

Information

To fulfill its role, the genetic material must meet several criteria

2. __________: It must be passed from parent to offspring

transmission

To fulfill its role, the genetic material must meet several criteria

_________: It must be copied
- In order to be passed from parent to offspring

replication

To fulfill its role, the genetic material must meet several criteria

4. _________: It must be capable of changes
- To account for the known phenotypic variation in each species

variation

To fulfill its role, the genetic material must meet several criteria

n 1. ______: It must contain the information necessary to make an entire organism

n 2. _______: It must be passed from parent to offspring

n 3. _______: It must be copied
n In order to be passed from parent to offspring

n 4. _______: It must be capable of changes
n To account for the known phenotypic variation in each species

information; transmission; replication; variation

Griffith studied a bacterium (pneumococci) now known as _______ _______

Streptococcus pneumoniae

S. pneumoniae comes in two strains

S → Smooth

• Secretes a _____ capsule

  • Protects bacterium from the _____ system of animals

• Produce smooth colonies on solid media

polysaccharide; immune

S. pneumoniae comes in two strains

R → Rough

• _____ to secrete a capsule

• Produce colonies with a rough appearance

Unable

In 1928, Griffith conducted experiments using two strains of S. pneumoniae: type IIIS (smooth) and type IIR (rough)

What happens when mouse was injected with live type IIIS bacteria?

Mouse died, type IIIS bacteria recovered from the mouse’s blood

In 1928, Griffith conducted experiments using two strains of S. pneumoniae: type IIIS (smooth) and type IIR (rough)

What happens when mouse was injected with live type IIR bacteria?

Mouse survived, no living bacteria isolated from the mouse’s blood

In 1928, Griffith conducted experiments using two strains of S. pneumoniae: type IIIS (smooth) and type IIR (rough)

What happens when mouse was injected with heat-killed type IIIS bacteria?

Mouse survived, no living bacteria isolated from the mouse’s blood

In 1928, Griffith conducted experiments using two strains of S. pneumoniae: type IIIS (smooth) and type IIR (rough)

What happens when mouse was injected with live type IIR + heat-killed type IIS cells?

Mouse died, type IIIS bacteria recovered from the mouse’s blood

From the mouse experiments, Griffith found out that something from the dead type IIIS was transforming type IIR into type IIIS

He called this process ________

transformation

The substance that allowed this to happen was termed the _____ _____

• Griffith did not know what it was

transformation principle

Avery, MacLeod and McCarty identified the transforming principle (genetic material) as ______

DNA

Avery, MacLeod and McCarty identified the transforming principle (genetic material) as DNA

They prepared _____ _____ (DNA, RNA, proteins and carbohydrates) from type IIIS cells containing each of these macromolecules

cell extracts

Only the extract that contained _____ DNA was able to convert type IIR into type IIIS

purified

Treatment of the extract with _____ eliminate transformation

Treatment with RNase or protease did not eliminate transformation

DNAse

In 1952, Alfred Hershey and Marsha Chase provided further evidence that DNA is the genetic material

• They studied the bacteriophage T2

• It is relatively simple since its composed of only two macromolecules: _____ and _____
  

DNA; protein

Life cycle of the T2 bacteriophage

-has to inject its “____ ____” into the host cell to direct its propagation

The Hypothesis

• Only the genetic material of the phage is injected into the bacterium

• Isotope labeling will reveal what is injected into the bacterium (if it is DNA or protein?)

genetic material

The Hershey and Chase experiment can be summarized as such:

• Used radioisotopes to distinguish DNA from proteins

  • 32P labels ___ specifically

  • 35S labels ____ specifically

DNA; protein

Radioactively-labeled phages were used to infect nonradioactive Escherichia coli cells

After allowing sufficient time for infection to proceed, the residual phage particles were sheared off the cells

• => Phage ghosts and E. coli cells were separated via centrifugation

Radioactivity was monitored using a ______ ______

scintillation counter

The results suggest that DNA is injected into the bacterial ____ during infection

• This is the expected result if DNA is the genetic material

cytoplasm

Is it true that RNA functions as the genetic material in some viruses?

Yes

In 1956, A. Gierer and G. Schramm isolated RNA from the tobacco mosaic virus (TMV, a plant virus) which infects and causes lesions in plants

• ____ _____ caused the same lesions as intact TMV viruses

• Therefore, the viral genome is composed of RNA

purified RNA

DNA and RNA are large _____ with several levels of complexity

macromolecules

1. ______ form the repeating units

nucleotides

Nucleotides are linked to form a ______

strand

Nucleotides form the repeating units

Nucleotides are linked to form a strand

Two strands can interact to form a _____ _____ (DNA) –remember RNA molecules are primarily single stranded

double helix

Is DNA double-stranded or single-stranded?

double-stranded

Is RNA double-stranded or single-stranded?

single-stranded

The double helix DNA folds, bends and interacts with proteins resulting in 3-D structures in the form of _______

chromosomes

The _______ is the repeating structural unit of DNA and RNA

nucleotide

The nucleotide is the repeating structural unit of DNA and RNA.

It has three components. What are they?

a phosphate group, a pentose sugar, a nitrogenous base

What is the sugar found in DNA?

deoxyribose

What is the sugar found in RNA?

ribose

What are the purines?

Adenine and Guanine

What are the Pyrimidines?

Thymine and Uracil and Cytosine?

Is uracil found in DNA?

No

Do purines have a double ring or single ring?

double ring

Do pyrimidines have a double ring or a single ring?

single ring

Is Thymine found in RNA?

No

Base + sugar + phosphate → ?

Example

Adenosine monophosphate (AMP)

Adenosine diphosphate (ADP)

Adenosine triphosphate (ATP)

nucleotide

Phosphate is always attached to the __’ side of the ribose

5’

Base is always attached to the ___’ side of the ribose

1’

The difference between ribose and deoxyribose is that ribose has an extra OH on the __’ side

2’

Nucleotides are ____ linked together by ____ bonds

covalently; phosphodiester

A phosphate connects the __’ carbon of one nucleotide to the _’ carbon of another.

5'; 3’

A strand has directionality ____’ to ___’

5’; 3’

A Few Key Events Led to the Discovery of the Structure of DNA

In 1953, James Watson and Francis Crick discovered the ____ _____ structure of DNA

The scientific framework for their breakthrough was provided by other scientists including:

Rosalind Franklin and Maurice Wilkins

Erwin Chargaff

double helical

Rosalind Franklin

She made marked advances in __-____ _____ techniques with DNA

x-ray diffraction

The _____ _____ Rosalind Franklin obtained suggested several structural features of DNA

• Helical

• More than one strand

• 10 base pairs per complete turn

diffraction pattern

Erwin Chargaff’s Experiment

• Chargaff pioneered many of the biochemical techniques for the isolation, purification and measurement of nucleic acids from living cells

• It was already known then that DNA contained the four bases: A, G, C and T

• Chargaff analyze the _____ _____ of DNA in different species

base composition

The compelling observation was that
Percent of _____ = percent of ____

Percent of _____ = percent of _____

adenine; thymine, guanine; cytosine

Percent of adenine = percent of thymine

Percent of guanine = percent of cytosine

This observation became known as _____ _____

It was crucial evidence that Watson and Crick used to elucidate the structure of DNA

Chargaff’s rule

The DNA Double Helix

• General structural features (Figures 9.17 & 9.18)

  • Two strands are twisted together around a common axis

• There are __ bases and 3.4 nm per complete twist

10

• The two strands are _________

  • One runs in the 5’ to 3’ direction and the other 3’ to 5’

antiparallel

• The helix is ____-___

• As it spirals away from you, the helix turns in a clockwise direction

right-handed

The DNA Double Helix

The double helix structure is stabilized by

1.) ______ bonding between _____ ____

n A bonded to T by two hydrogen bonds

n G bonded to C by three hydrogen bonds

hydrogen; complementary bases

The DNA Double Helix

The double helix structure is stabilized by

2. ______ interaction between bases

(Base stacking)

• Within the DNA, the bases are oriented so that the flattened regions are facing each other

• The planar surface of bases are hydrophobic (water insoluble

Hydrophobic

A bonded to T by ___ hydrogen bonds

2

G bonded to C by ____ hydrogen bonds

3

There are two asymmetrical grooves on the outside of the helix

1. ____ groove

2. ____ groove

major; minor

There are two asymmetrical grooves on the outside of the helix

1. Major groove

2. Minor groove
Certain proteins can bind within these grooves

They can thus interact with a particular sequence of ____

These proteins binding to the groves may alter DNA structure and regulate gene expression

bases

The DNA double helix can form different types of secondary structure

The predominant form found in living cells is ___-____

B-DNA

The DNA double helix can form different types of secondary structure

The predominant form found in living cells is B-DNA

However, under certain in vitro conditions, ___-DNA and __-DNA double helices can form

A; Z

Is A-DNA right-handed helix or left-handed helix?

right-handed

How many bp per turn does A-DNA have?

11 bp

A-DNA occurs under conditions of ____ ____

low humidity

Is A-DNA biologically important?

no, there is little evidence suggesting this

Is Z-DNA right-handed or left-handed?

left-handed

How many bp per turn does Z-DNA have?

12 bp

For Z-DNA, evidence from yeast suggests it may play a role in _____ and _____

transcription; recombination

In A-DNA, bases substantially ____ relative to the central axis

titled

In B-DNA, bases relatively ____ to the central axis

perpendicular

In Z-DNA, bases substantially ____ relative to the central axis

tilted

The Three-Dimensional Structure of DNA

• To fit within a living cell, the DNA double helix must be extensively compacted into a 3-D conformation

• This is aided by ____-____ _____

DNA-binding proteins

DNA double helix is compacted into a 3-D conformation by what?

DNA-binding proteins

DNA is wound around ____ proteins

histone

The primary structure of an RNA strand is much like that of a DNA strand

• Compare Figures 9.16 & 9.7

• RNA uses ____ as a base

uracil

• RNA uses ____ (what sugar?) with ___’ ___ (what chemical)

ribose; 2’; OH

RNA strands are typically several hundred to several thousand nucleotides in length

In RNA synthesis, only ___ of the two strands of DNA is used as a template

one

Although usually ____-____, RNA molecules can form short double- stranded regions

single-stranded

Although usually single-stranded, RNA molecules can form short double- stranded regions

• This secondary structure is due to _____ ____-____

• A to U and C to G

• Allows short regions to form a double helix

complementary base-pairing