Unit 3.1

Two different ___ of a given element have the SAME number of ___ (of course), but each has a DIFFERENT number of ___ in its nucleus

isotopes, protons, neutrons

Having DIFFERENT number of NEUTRONS makes an atomic nucleus ___

unstable

____ is the process by which an unstable atomic nucleus loses energy by emitting ionizing particles or radiation

Radioactive Decay

If we build a molecule with a_____ (like DNA with radioactive
phosphorus, or protein with radioactive sulfur) we can now "see" or "trace" where the molecule is

radioactive element

The discovery of the genetic role of DNA began with research by _____ in 1928

Frederick Griffith

Griffith worked with two strains of Streptococcus pneumoniae one pathogenic (____) and one harmless (____)

smooth, rough

The smooth bacteria produced a ____ that makes it impossible for
____ to occur - thus lethal

peptidoglycan, phagocytosis

When he mixed heat-killed remains of the pathogenic strain with living cells of the harmless strain, some living cells became pathogenic

he called this _____, now defined as a change in ____ and
____ due to assimilation of foreign or external DNA

phenomenon transformation, genotype, phenotype

The material that was responsible for the transformation was called___

transforming factor

n 1944, ____, ____, and ____ announced that the transforming substance was DNA

Avery, McCarty, Macleod

They did some ____ biology and isolated the nucleic acids, proteins, and sugars, and re-ran Griffith experiment instead of using whole bacteria

reductionist

Conclusion of Avery, McCarty, Macleod

Only DNA worked in transforming harmless bacteria into pathogenic bacteria

1952, ____ and ____ performed experiments showing that DNA is the genetic material of a phage (virus) known as T2

Hershey, Chase

Hershey and Chase concluded that the ___ ___ of the phage provides the genetic information

injected DNA

1950, ___ reported that DNA composition varies from one species to the next

Chagraff

Chargaff’s rules state that in any species there is an ___ number of A and T bases, and an ___ number of G and C bases

equal

____ and ___ were using a technique called X-ray
crystallography to study molecular structure (produced picture of DNA)

Wilkins, Franklin

The X-Ray images enabled ___ to conclude that DNA is ___ and the width and spacing of ____ bases thus concluding it is double helix

Watson, helical, nitrogenous

___ and ___ built models of a double helix to conform to the X-rays and chemistry of DNA

Watson, Crick

Watson and Crick noted that the specific ____ suggested a possible copying mechanism for genetic material

base pairing

Watson and Crick proposed a_____ of DNA replication ((derived
or “conserved” from the parent molecule))

semiconservative model

Competing models were
a. the _____ model (the two parent strands rejoin)
b. the ____ model (each strand is a mix of old and new)

conservative, dispersive

Experiments by ___ and ____ supported the semiconservative model

Meselson, Stalh

Helicase

Untwists the Double helix

Topoisomerase

relieves the strain of twisting caused by unwinding (breaks
swivels and regions bonds

Primase

Makes a primer (a starting point) for synthesis of a DNA strand

Polymerase

polymerizes a new strand of DNA by adding nucleotides

Ligase

ligates or joins together nucleic acids

Replication begins at special sites called_____, where the two DNA strands are separated, opening up a replication ___

origins of replication, bubble

Enzymes called ____ catalyze the elongation of new DNA at a replication
fork

DNA polymerases

Each nucleotide that is added to a growing DNA strand is a

nucleoside triphosphate

___, for example, supplies adenine to DNA and is similar to the ATP of energy
metabolism

dATP

____ proofread newly made DNA, replacing any incorrect nucleotides

DNA polymerases

In ____ of DNA,___correct errors in base pairing

mismatch repair, repair enzymes

In ____, a __ cuts out and replaces damaged stretches of
DNA

nucleotide excision repair, nuclease

Eukaryotic chromosomal DNA molecules have at their ends nucleotide sequences
called ____

telomeres

It has been proposed that the ____ of telomeres is connected to aging

shortening

An enzyme called ___ catalyzes the lengthening of telomeres in germ cells

telomerase