BIOLOGY CH 5

Question 1

The place where helicase begins to unwind is a specific sequence of nucleotides on the chromosome called the __________ .

Answer 1

Origin of replication (ORI)

Question 2

A chromosome would get tangled and eventually break, except that enzymes called ___________ cut one or both strands and unwrap the helix, releasing the excess tension created by the helicases.

Answer 2

Topoisomerase

Question 3

An ______ primer must be synthesized for each template strand because DNA polymerase cannot start a new DNA chain from scratch.

Answer 3

RNA

Question 4

RNA primer is synthesized by a set of proteins called the ____________, of which the central component is an ____________ called ____________.

Answer 4

RNA primer is synthesized by a set of proteins called the primase, of which the central component is an RNA polymerase called primase.

Question 5

DNA polymerase reads the template strand in which direction?

Answer 5

From 3’ to 5’

Question 6

DNA polymerase elongates a daughter strand by adding dNTPs to its _____ end.

Answer 6

3’

Question 7

DNA pol is part of a large complex of proteins called the ________________ .

Answer 7

Replisome

Question 8

The prokaryotic replisome contains __ components and the eukaryotic replisome contains __ components. Additional complexity in the eukaryotic system is required because replication machinery must also ___________ .

Answer 8

13 components prokaryotes; 27 components eukaryotes; unwind DNA from histone proteins

Question 9

T/F: DNA pol checks each new nucleotide to make sure it forms a correct base-pair

Answer 9

True

Question 10

The driving force for the polymerization reaction of DNA synthesis is?

Answer 10

The removal and hydrolysis of pyrophosphate (P2O7) from each new dNTP added to the chain

Question 11

Eventually all RNA primers are replaced by DNA, and the fragments are joined by an enzyme called ____________ .

Answer 11

DNA ligase

Question 12

T/F: Eukaryotes have several different DNA polymerase enzymes?

Answer 12

True

Question 13

T/F: In eukaryotic replication, each chromosome has one ORI?

Answer 13

False, each chromosome has several

Question 14

T/F: In prokaryotic replication, the one chromosome only has one origin?

Answer 14

True

Question 15

_____________ are disposable repeats at the end of chromosomes. They are consumed and shorten during cell division.

Answer 15

Telomeres

Question 16

When ________ becomes too short, they reach a critical length where the chromosome can no longer replicate.

Answer 16

Telomeres

Question 17

What is the Hayflick limit?

Answer 17

The number of times a normal human cell type can divide until telomere length stops cell division

Question 18

__________ is an enzyme that adds repetitive nucleotide sequences to the ends of chromsomes and therefore lengthens _________ .

Answer 18

Telomerase; telomeres

Question 19

______________ can express telomerase, which can help the cells immortalize.

Answer 19

Cancer cells

Question 20

What does it mean when a cell enters a ‘senescent state?’

Answer 20

Where they are alive but not dividing

Question 21

What are 3 things a cell can do when their telomeres become too short?

Answer 21

1. Active DNA repair pathways
2. Enter a senescent state
3. Apoptosis

Question 22

What are germline mutations?

Answer 22

Mutations that can be passed onto offspring, since they occur in the germ cells (which give rise to gametes).

Question 23

What do germ cells give rise to?

Answer 23

Gametes

Question 24

T/F: Somatic mutations cannot pass onto offspring?

Answer 24

True

Question 25

What is a mutagen?

Answer 25

Any compound that can cause mutations

Question 26

Name things that chemical can do to DNA structure

Answer 26

1. covalently alter bases
2. cross-linking
3. strand breaks

Question 27

What does intercalating mean?

Answer 27

When compounds that look like purines and pyrimidines cause mutations by inserting themselves between base pairs

Question 28

What is a transition point mutation?

Answer 28

Purine for another purine/Pyrimidine for another pyrimidine

Question 29

What is a transversion point mutation?

Answer 29

Purine for a pyrimidine and vice-versa

Question 30

Define missense mutation.

Answer 30

A point mutation that results in one amino acid being replaced with a different amino acid

Question 31

Define nonsense mutation.

Answer 31

A stop codon replaces a regular codon and prematurely shortens the protein

Question 32

Define silent mutation.

Answer 32

A codon is changed into a new codon for the same amino acid, so there is no change in the protein’s amino acid sequence

Question 33

An ________ is when a segment of chromosome is reversed end to end.

Answer 33

Inversion

Question 34

What is chromosome amplification?

Answer 34

When a segment of a chromsome is duplicated, similar ot copy number variation

Question 35

What is translocation?

Answer 35

When recombination occurs between nonhomologous chromosomes. This can create a gene fusion, where a new gene product is made from parts of two genes that were not previously connected.

Question 36

When ________ are mobilized, they can insert in any part of the genome and this can affect gene expression or cause mutations.

Answer 36

Transposons

Question 37

What is hemizygous?

Answer 37

When there is only one gene copy (allele) in a diploid organism.

Question 38

Oncogene defined.

Answer 38

A gene that can cause cancer when it is mutated or expressed at high levels