11 Ap Bio Ch. 14-16

Front 1

DNA contains many different genes that are transcribed into different:

Back 1

mRNAs, tRNAs, and rRNAs

Front 2

An RNA molecule is:

a double helix
OR
usually single-stranded

Back 2

usually single-stranded

Front 3

An mRNA molecule is produced by ________.

Back 3

transcription

Front 4

Each codon calls for a specific:

Back 4

amino acid

Front 5

Anticodons pair with ______.

Back 5

mRNA codons

Front 6

______ are base sequences that must be removed before a pre-mRNA molecule can be translated.

Back 6

introns

Front 7

_______ are the parts that are still in the mRNA when it has translated into protein.

Back 7

exons

Front 8

Transcription is initiated at a _________.

Back 8

promoter

Front 9

What three key respects makes transcription different from DNA replication?

Back 9

1. only ONE region of ONE DNA strand is used as a template.
2. instead of DNA polymerases, the type of enzyme known as RNA polymerase catalyzes nucleotide additions to a growing RNA strand.
3. at the end of transcription there is a single, free strand of RNA nucleotides, not a double helix

Front 10

During gene transcription, adenine base-pairs with ______, and guanine with _______.

Back 10

uracil
cytosine

Front 11

_______ are the only molecules that carry protein-building instructions from DNA into the cytoplasm.

Back 11

mRNAs

Front 12

Ribosomes are composed of what 2 things?

Back 12

rRNA and proteins

Front 13

Each kind of tRNA has a(n) _______ that is complementary to an mRNA _______.

Back 13

anticodon
codon

Front 14

Enzymes, which can restrict bacteriophage growth in a host cell, are now called:

Back 14

restriction enzymes

Front 15

What is a genome?

Back 15

all of the DNA in a haploid number of chromosomes for a species

Front 16

Restriction enzymes cut DNA at a specific sequence.
What is the difference between blunt and sticky ends?

Back 16

*sticky: a restriction fragment's single-stranded tail can base-pair w/ a complementary tail of any other DNA fragment or molecule cut by the same restriction enzyme = this will form a recombinant DNA molecule sealed by DNA ligase
*blunt:
ATGTCA
TACAGT (nothing hanging off)

Front 17

What is a plasmid?

Back 17

a very small circle of extra DNA that has just a few genes and that gets replicated along with the bacterial chromosome

Front 18

Explain the process to make a DNA clone.

Back 18

(before cell division, replication enzymes replicated the plasmid, so a cell can hold many identical copies of foreign DNA)
in research laboratories, foreign DNA typically is inserted into a plasmid for replication
-the outcome is a DNA clone, b/c bacterial cells have made many identical, "cloned" copies of it

Front 19

A DNA strand "copied" from a mature mRNA transcript is called:

Back 19

cDNA (complementary DNA)

Front 20

______________ catalyzes transcription in reverse.
Explain.

Back 20

Reverse transcriptase
-this enzyme from RNA viruses builds a complementary DNA strand on an mRNA transcript
-then other enzymes remove the RNA from the mRNA-cDNA molecule and substitute a complementary DNA strand
= the outcome is double-stranded cDNA

Front 21

The polymerase chain reaction, widely known as PCR, is another way to _______ fragments of chromosomal DNA or cDNA

Back 21

amplify

Front 22

What are primers?

Back 22

*used in polymerase chain reaction
-synthetic, short nucleotide sequences, ten to 30 or so nucleotides long, that can base-pair w/ complementary sequences in DNA
-DNA polymerases recognize them as START tags

Front 23

Explain the PCR process. (amplifying DNA)

Back 23

*at the beginning of each temperature cycle, the 2 strands of all molecules of DNA in the mixture unwind from each other
*primers become positioned on exposed nucleotides at targeted sites according to base-pairing rules
-DNA polymerases recognize the primers as START tags and assemble complementary sequences on the strands = this doubles the number of identical DNA fragments

Front 24

PCR is far more rapid than ________ _________.

Back 24

cloning methods

Front 25

What do researchers use now to learn the sequence of cloned DNA or PCR-amplified DNA in only a few hours?

Back 25

automated DNA sequencing

Front 26

Standard nucleotides include dATP, dTTP, dCTP, and dGTP.
What is the importance of the modified versions of nucleotides in automated DNA sequencing?

Back 26

represented as T*, C*, A*, and G*
*ddNTP = dideoxydNTP = no 3'-OH which his required to have for DNA polymerase
-each modified version is labeled with a molecule that fluoresces a certain color when it passes through a laser beam
-every time one of these modified nucleotides get incorporated into a growing DNA strand, it arrests DNA synthesis

Front 27

After the primer binds with its complementary sequence, DNA polymerase synthesizes a new DNA strand. Suppose the polymerase encounters a T in a DNA template strand. What 2 things might happen?

Back 27

-it will catalyze the base-pairing of either A or A* to it
*if A is added to the new strand, replication will continue
*if A* is added to the new strand, replication will stop; the modified nucleotide will block addition of any more nucleotides to that strand

Front 28

Because either a standard or a modified nucleotide could be added at every exposed base, the new strands end at _________ locations in the sequence.

Back 28

different

Front 29

What is the role of the automated DNA sequencer?

Back 29

*separates the sets of fragments by gel electrophoresis
-b/c the fragments all have a modified nucleotide at the 3' end, each set fluoresces a certain color as it passes through a laser beam
-automated sequencer detects the color and indicates which nucleotide is on the end of the fragments in each set
-it assembles the information from all nucleotides in the sample, and in this way it reveals the entire DNA sequence

Front 30

A mixed collection of bacteria that contain different cloned DNA fragments is called:

Back 30

a gene library
-used when you want to isolate a gene from all others in a genome

Front 31

What is a probe?

Back 31

a very short stretch of DNA labeled with a radioisotope so that it can be distinguished from other DNA molecules in a given sample
-part of the probe must be able to base-pair with some portion of the gene of interest

Front 32

Any base-pairing that takes place between sequences of DNA (or RNA) from different sources is called:

Back 32

nucleic acid hybridization

Front 33

What are the 5 steps for the screening for genes?

Back 33

1.Grow the bacterial colonies on suitable medium in a petri plate.
2.Place a nylon filter over the colonies and lift some cells off.
3.Place the filter in a solution to disrupt the cells but leave DNA sticking to the filter.
4.Add a radioactively-labeled probe DNA to the filter where it will bind to the DNA fragments of complementary sequence.
5.Expose the filter to x-ray film to locate the gene of interest, which will be in the same location as the cells in the petri plate.