Biochemistry Lecture 17

Front 1

Replication of linear eukaryotic chromosomes is more complex than

Back 1

Replication of linear eukaryotic chromosomes is more complex than replicating the circles of prokaryotic cells.

Front 2

During each round of eukaryotic DNA replication, a small portion of the DNA at the end of the chromosome (known as a telomer) is

Back 2

During each round of eukaryotic DNA replication, a small portion of the DNA at the end of the chromosome (known as a telomer) is lost.

Front 3

Telomers have

Back 3

Telomers have thousands of copies of the same short nucleotide sequence.

Front 4

Telomer length may be relative

Back 4

Telomer length may be relative the cellular lifespan.

Front 5

Telomerases are

Back 5

Telomerases are enzymes that make telomers

Front 6

Telomerases are enzymes that make telomers and they are active in

Back 6

Telomerases are enzymes that make telomers and they are active in fetal cells.

Front 7

Telomerases serve to

Back 7

Telomerases serve to elongate the ends of linear chromosomal DNAs, adding thousands of repeats of a short sequence (junk DNA). This "junk DNA" is called a telomere.

Front 8

At each round of eukaryotic DNA replication, a short stretch at the end of the DNA is lost, shortening

Back 8

At each round of eukaryotic DNA replication, a short stretch at the end of the DNA is lost, shortening the telomere.

Front 9

The longer a telomere is, the more

Back 9

The longer a telomere is, the more times a cell can divide before it starts losing important DNA sequences.

Front 10

________cells are another cell type that has an active telomerase.

Back 10

Tumor cells are another cell type that has an active telomerase. This probably is a factor that enables them to be "immortal".

Front 11

Telomerase acts as a

Back 11

Telomerase acts as a reverse transcriptase

Front 12

Telomerase acts as a reverse transcriptase, using a

Back 12

Telomerase acts as a reverse transcriptase, using an RNA primer that it carries with it to copy and make the repetitive sequences of the telomer.

Front 13

Eukaryotic cells tightly control

Back 13

Eukaryotic cells tightly control the process that leads to their division.

Front 14

Eukaryotic cells tightly control the process that leads to their division. The cycle is called

Back 14

Eukaryotic cells tightly control the process that leads to their division. The cycle is called the cell cycle

Front 15

The protein _____ plays an important role in the cell cycle

Back 15

protein p53 plays an important role in the cell cycle

Front 16

If p53 detects that replication has not completed properly, it

Back 16

If p53 detects that replication has not completed properly, it stimulates production of repair proteins that try to fix the damage.

Front 17

If the damage is fixed,

Back 17

If the damage is fixed, the cell cycle continues and the cell ultimately divides.

Front 18

If the damage cannot be fixed, p53 stimulates

Back 18

If the damage cannot be fixed, p53 stimulates the cell to commit suicide - a phenomenon called apoptosis.

Front 19

Transcription is

Back 19

Transcription is the making of RNA using DNA as a template.

Front 20

Transcription requires

Back 20

Transcription requires an RNA polymerase, a DNA template and 4 ribonucleoside triphosphates (ATP, GTP, UTP, and CTP).

Front 21

Prokaryotic cells have only a single

Back 21

Prokaryotic cells have only a single RNA polymerase.

Front 22

Transcription occurs in the_____ direction

Back 22

Transcription occurs in the 5' to 3' direction.

Front 23

RNA polymerases differ from DNA polymerases in

Back 23

RNA polymerases differ from DNA polymerases in the RNA polymerases do NOT require a primer.

Front 24

Transcription requires DNA strands to be

Back 24

ranscription requires DNA strands to be opened to allow the RNA polymerase to enter and begin making RNA

Front 25

ranscription starts near special DNA sequences called

Back 25

Transcription starts near special DNA sequences called promoters.

Front 26

A factor known as _____ associates with the RNA polymerase in E. coli and helps it to recognize and bind to the promoter.

Back 26

A factor known as sigma associates with the RNA polymerase in E. coli and helps it to recognize and bind to the promoter.

Front 27

A promoter is a

Back 27

A promoter is a sequence in DNA that is recognized by the RNA Polymerase-Sigma complex.

Front 28

Sigma factor binds to BOTH

Back 28

Sigma factor binds to BOTH the RNA Polymerase and to the promoter sequence in the DNA.

Front 29

sigma factor is a

Back 29

sigma factor is a PROTEIN

Front 30

Genes that are to be transcribed have a ________close by to facilitate RNA Polymerase binding to begin transcription.

Back 30

Genes that are to be transcribed have a promoter close by to facilitate RNA Polymerase binding to begin transcription.

Front 31

Promoters in E. coli have ___ common features.

Back 31

2

Front 32

Promoters in E. coli have two common features. The first is

Back 32

Promoters in E. coli have two common features.

The first is a sequence usually located about 10 base pairs "upstream" of the transcription start site (the transcription start site is the location where the first base of RNA starts).

Front 33

Promoters in E. coli have two common features. The first is a sequence. This sequence is known as the_____ or _____

Back 33

This sequence is known as the "-10" sequence or the Pribnow box.

Front 34

"-10" sequence or the Pribnow box', is so-named because

Back 34

The "-10" sequence or the Pribnow box', which is so-named because the most common version of it (known as a consensus sequence) has the sequence 5'-TATAAT-3'.

Front 35

The second common feature of E. coli promoters is located

Back 35

The second common feature of E. coli promoters is located about 35 base pairs upstream of the transcription start site.

Front 36

Eukaryotic promotoers also frequently have a ________ but

Back 36

Eukaryotic promotoers also frequently have a TATA box, but in a slightly different position.

Front 37

Transcription occurs in three phases

Back 37

Transcription occurs in three phases - initiation, elongation, and termination.

Front 38

Binding of RNA Polymerase and sigma is

Back 38

Binding of RNA Polymerase and sigma is the first step in transcription (initiation).

Front 39

After polymerization starts, _____________ leaves the RNA polymerase and the elongation process continues.

Back 39

After polymerization starts, sigma factor leaves the RNA polymerase and the elongation process continues.

Front 40

Termination of transcription in E. coli occurs by _________ mechanisms.

Back 40

Termination of transcription in E. coli occurs by several mechanisms.

Front 41

Termination of transcription in E. coli occurs by (example)

Back 41

factor independent transcription termination

Front 42

Termination of transcription in E. coli occurs by Factor independent transcription termination, which occurs as a result of ______________.

Back 42

Termination of transcription in E. coli occurs by Factor independent transcription termination, which occurs as a result of a hairpin loop forming in the sequence of an RNA.

Front 43

When the hairpin loop forms it

Back 43

it "lifts" the RNA polymerase off the DNA and everything falls apart and transcription stops at that point.

Front 44

Factor dependent termination and is caused by a protein called

Back 44

Factor dependent termination and is caused by a protein called rho.

Front 45

Rho works by

Back 45

Rho works by binding to the 5' end of the RNA and sliding up the RNA faster than the RNA Polymerase makes RNA. When rho catches the RNA polymerase, it causes the RNA polymerase to dissociate (come off of) the DNA and release the RNA.