What was Meselson and Stahl's experiment ? What did they do ?

 Meselson and Stahl experiment demonstrated the correctness of the semiconservative model of DNA replication. They did this by completing the following steps: 

1. Bacteria grown in 14N or 15N medium.
2. Samples removed and DNA extracted.
3. Examine to check density of DNA 

What enzyme catalyzes the elongation of a DNA strand in the 5' to 3' direction ?

DNA Polymerase

What base pairs pair with each other ?

Guanine pairs with Cytosine

Thymine pairs with Adenine (Adenine pairs with Uracil in RNA)

The RNA polymerase must

recognize a promoter

Which of the RNA molecule carries information as it is needed for the construction of a protein ?

Messenger RNA (mRNA)

What did Oswald Avery show ?

Avery showed isolated DNA as the

material of which genes and

chromosomes are made.

The enzymes responsible for adding nucleotides to the exposed DNA template bases are?

DNA Polymerase 

What does a nucleotide consist of ? 

A nitrogenous base, which can be either adenine, guanine, cytosine, or thymine (in the case of RNA, thymine is replaced by uracil). A five-carbon sugar, called deoxyribose because it is lacking an oxygen group on one of its carbons. One or more phosphate groups.

During translation, the amino acid detaches from the transfer RNA molecule amd attaches to the end of a growing protein chain when ?

The transfer RNA anticodon binds to

the messenger RNA codon.

Where on the lac operon does a

repressor molecule bind when

lactose is absent?

To the Operator

What are the different types of RNA? 

 4 types of RNA, each encoded by its own type of gene:

mRNA (MessengerRNA): Encodes amino acid sequence of a polypeptide.

tRNA (Transfer RNA): Brings amino acids to ribosomes during translation.

rRNA (Ribosomal RNA): With ribosomal proteins, makes up the ribosomes, the organelles that translate the mRNA

snRNA (Small nuclear RNA): With proteins, forms complexes that are used in RNA processing in eukaryotes. (Not found in prokaryotes.)

How do the leading and lagging strand differ ?

They differ in that the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction and the leading strand is synthesized continuously, whereas the lagging strand is synthesized in short fragments that are ultimately stitched together.

What happens during transcription? 

During transcription, RNA polymerase seperates

DNA strands and uses one of the strands as a

template to assemble nucleotides into a

complementary strand of RNA.

Ribozyme 

RNA molecule capable of acting as an enzyme.

What is the arrangement of an Okazaki fragment ?

 5' RNA nucleotides, DNA

nucleotides 3' 

What shuts off the Lac operator?

Low or high glucose levels and low lactose levels result in repressor protein from restricting transcription of lac operon

DNA Structure

(The Double Helix) DNA is made up of six smallermolecules -- a five carbon sugar called deoxyribose, a phosphate molecule and four different nitrogenous bases (adenine, thymine, cytosine and guanine).

The genetic code is essentially the same for all organisms. What can be assumed from this ?

A gene from an organism can

theoretically be expressed by any

other organism.

In what direction does RNA polymerase move ?

3' → 5'

What is an operator ?

A short DNA region, adjacent to the promoter of

a prokaryotic operon, that binds repressor

proteins responsible for controlling the rate of

transcription of the operon