BSC 2010 exam 3

isotopes

Different forms of the same element

isotopes

____________ Have different numbers of neutrons in the nucleus

same, different

Two different isotopes of a given element have the ______ number of PROTONS (of course), but each has a ____________ number of NEUTRONS in its nucleus.

Radioactive decay

________________is the process by which an unstable atomic nucleus loses energy by emitting ionizing particles or radiation.

different, unstable

Having __________ number of NEUTRONS makes an atomic nucleus _________

normal

isotopes have the ___________ number of electrons, so behave well in chemical reactions.

see or trace

If we build a molecule with a radioactive element (like DNA with radioactive phosphorus, or protein with radioactive sulfur) we can now _______________ where the molecule is.

Griffith

demonstrations of bacterial transformation

Avery McCarty and MacLeod

Transforming factor is separable

Hershey and Chase

Transforming factor is DNA

Chargaff

Ratios of DNA within and between species

Watson and Crick

DNA structure

Franklin

DNA structure

Meselson and Stahl

Semi-conservative replication

Griffith's experiment

the once "R" bacteria were now "S" and were now "S" permanently, generation after generation, defined as a change in genotype and phenotype due to assimilation of foreign or external DNA

Avery, McCarty and Macleod experiment

Their conclusion was based on experimental evidence that only DNA worked in transforming harmless bacteria into pathogenic bacteria and biologists remained skeptical, mainly because little was known about DNA

Viruses

_______ work by injecting their genetic material into the host cell.

Hershey and Chase

They concluded that the injected DNA of the phage provides the genetic information. isolated the phage then grew each type (radioactive protein and radioactive DNA) it in bacteria in two separate flasks.

Chargaff's rules

___________ ___________ state that in any species there is an equal number of A and T bases, and an equal number of G and C bases

Watson-Crick model

The ________________ ___________ explains Chargaff's rules: in any organism the amount of A = T, and the amount of G = C

double helix

The relationship between structure and function is manifest in the ____________ ______

Watson and Crick experiment

noted that the specific base pairing suggested a possible copying mechanism for genetic material

replicated

Every time a cell divides DNA must be_____

3 billion

human genome copying____ __________ bits of information with high fidelity

template

the two strands of DNA are complementary, each strand acts as a _____ for building a new strand in replication

DNA replication,

_________ _________the parent molecule unwinds, and two new daughter strands are built based on base-pairing rules

semiconservative model

Watson and Crick's ___________ __________ of replication predicts that when a double helix replicates, each daughter molecule will have one old strand (derived or "conserved" from the parent molecule) and one newly made strand

semiconservative, conservative, dispersive

3 models were

Meselson and Stahl

They labeled the nucleotides of the old strands with a heavy isotope of nitrogen, while any new nucleotides were labeled with a lighter isotope. Their results support semiconservative replication

speed, accuracy

The copying of DNA is remarkable in its ______ and __________

enzymes, proteins

More than a dozen ______and other ____ participate in DNA replication

Helicase

Untwists the Double helix

Topoisomerase

believes 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

enzymes

Helicase, Topoisomerase, Primase, Polymerase, Ligase

Replication

______begins at special sites called origins of replication, where the two DNA strands are separated, opening up a replication "bubble"

eukaryotic

A ______chromosome may have hundreds or even thousands of origins of replication

copied

Replication proceeds in both directions from each origin, until the entire molecule is ___________

replication fork

At the end of each replication bubble is a ________ ________, a Y-shaped region where new DNA strands are elongating

synthesis

DNA polymerases cannot initiate _______of a polynucleotide; they can only add nucleotides to the 3' end. The initial nucleotide strand is a short RNA primer, made by a primase

DNA polymerases

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

primer, template strand

Most DNA polymerases require a _______and a DNA ___________ ________

500, 50

The rate of elongation is about _________nucleotides per second in bacteria and _______per second in human cells

dATP

supplies adenine to DNA and is similar to the ATP of energy metabolism

deoxyribose, ribose

The difference is in their sugars: dATP has _______________while ATP has ________

nucleoside triphosphate

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

antiparallel

The __________________structure of the double helix (two strands oriented in opposite directions) affects replication

3'

DNA polymerases add nucleotides only to the free ____ end of a growing strand; therefore, a new DNA strand can elongate only in the 5' to 3' direction

proofread

DNA polymerases ________newly made DNA, replacing any incorrect nucleotides

mismatch repair

In ______________ ___________of DNA, repair enzymes correct errors in base pairing

nucleotide excision repair

in _______________ _______ _________, a nuclease cuts out and replaces damaged stretches of DNA

Limitations

________of DNA polymerase create problems for the linear DNA of eukaryotic chromosomes

shorter

The usual replication machinery provides no way to complete the 5¢ ends, so repeated rounds of replication produce _________ DNA molecules

telomeres

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

erosion

Telomeres do not prevent the shortening of DNA molecules, but they do postpone the _______of genes near the ends of DNA molecules

aging

It has been proposed that the shortening of telomeres is connected to __

genes

If chromosomes of germ cells became shorter in every cell cycle, essential ___________would eventually be missing from the gametes they produce

telomerase

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

nucleotides

The information content of DNA is in the form of specific sequences of _____

synthesis of proteins

the DNA inherited by an organism leads to specific traits by dictating the___________ ___ __________

Proteins

____________are the links between genotype and phenotype

Gene expression,

____________ _________ the process by which DNA directs protein synthesis,

transcription and translation

gene expression includes two stages:

one gene one protein

How was the fundamental relationship between genes and proteins discovered?

metabolic pathway

Linking genes to enzymes required understanding that cells synthesize and degrade molecules in a series of steps, a ____________ ______________

Archibald Garrod

first suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions

one gene-one enzyme hypothesis

which states that each gene dictates production of a specific enzyme

George Beadle and Edward Tatum

exposed bread mold to X-rays, creating mutants that were unable to survive on minimal medium as a result of inability to synthesize certain molecules

RNA

__________is the intermediate between genes and the proteins for which they code

Transcription

_______ is the synthesis of RNA under the direction of DNA

messenger RNA (mRNA)

Transcription produces

Translation

________is the synthesis of a polypeptide, which occurs under the direction of mRNA

Ribosomes

are the sites of translation

prokaryotes

In ________________, mRNA produced by transcription is immediately translated without more processing

eukaryotic

In a _____________cell, the nuclear envelope separates transcription from translation

transcripts

Eukaryotic RNA _________are modified through RNA processing to yield finished mRNA

primary transcript

A __________ _________ is the initial RNA transcript from any gene

central dogma

The_________ ______ is the concept that cells are governed by a cellular chain of command: DNA -> RNA -> protein

20 amino acids, only four nucleotide bases

How are the instructions for assembling amino acids into proteins encoded into DNA?

Triplets of Bases

How many bases correspond to an amino acid?

Codons

Triplets of Bases

triplet code

he flow of information from gene to protein is based on a _________________ _________: a series of nonoverlapping, three-nucleotide words

smallest

These triplets are the ____________units of uniform length that can code for all the amino acids

amino acid

AGT at a particular position on a DNA strand results in the placement of the_________ _______ serine at the corresponding position of the polypeptide to be produced

transcription

During ____________, one of the two DNA strands called the template strand provides a template for ordering the sequence of nucleotides in an RNA transcript

translation

During _____________, the mRNA base triplets, called codons, are read in the 5' to 3' direction

5' to 3'

Codons along an mRNA molecule are read by translation machinery in the _______ _____ __________ direction

one

Each codon specifies the addition of _______ of 20 amino acids

64

how many codons are there?

amino acids

Of the 64 triplets, 61 code for ____ ___

3 triplets

___________ _________ are "stop" signals to end translation

polypeptide

Codons must be read in the correct reading frame (correct groupings) in order for the specified ___________to be produced

transplanted

Genes can be transcribed and translated after being __________from one species to another

RNA polymerase

RNA synthesis is catalyzed by _________ ________________, which pries the DNA strands apart and hooks together the RNA nucleotides

RNA synthesis

_________ _______ follows the same base-pairing rules as DNA, except uracil substitutes for thymine

promoter

The DNA sequence where RNA polymerase attaches is called the _________;

terminator

n bacteria, the sequence signaling the end of transcription is called the _______

transcription unit

The stretch of DNA that is transcribed is called a __________ _________