Question 1

What is DNA replication?

Accepted Answer

The process of creating two identical DNA molecules, from a single original molecule

Question 2

What is conservative DNA replication?

Accepted Answer

An incorrect model of DNA replication where the original DNA molecule is unchanged

(an exact copy is made without changing the original; different from the semiconservative and dispersive models)

Question 3

What is semiconservative DNA replication?

Accepted Answer

A correct model of DNA replication where the new DNA has a helix from the original parent, as well as a newly created helix

(this is the correct model; different from the conservative and dispersive models)

Question 4

What is dispersive DNA replication?

Accepted Answer

An incorrect model of DNA replication where the newly created DNA contains some DNA of the original molecule, dispersed with new DNA

(different from the conservative and semiconservative models)

Question 5

What are the differences between conservative, semiconservative, and dispersive models of DNA replication?

Accepted Answer

Conservative keeps the original unchanged (incorrect)

Semiconservative causes the new DNA to have one strand of old DNA and one strand of new DNA (correct)

Dispersive causes the new DNA to have bits and pieces of the old DNA mixed with new DNA segments (incorrect)

Question 6

What was the Meselson–Stahl experiment?

Accepted Answer

An experiment that indicates DNA replication is semiconservative

Question 7

What is helicase?

Accepted Answer

An enzyme in DNA replication, that unzips the DNA, separating it into single strands and producing the replication fork

(essential for DNA replication, since it separates double strands of DNA into single strands that can be copied)

Question 8

What is the replication fork?

Accepted Answer

A structure that forms during DNA replication, with two branching "prongs" made of a single strand of DNA

(created by helicase)

Question 9

What are primer sites in DNA replication?

Accepted Answer

Short nucleic acid sequences along each DNA strand, that provide an origin site for where replication begins

(DNA polymerase can only attach nucleotides to existing strands of nucleotides, so primer sites are essential foundations)

Question 10

What is DNA polymerase?

Accepted Answer

Molecules in DNA replication that synthesize DNA by adding nucleotides one by one to the DNA chain

(start at the primer and expand)

Question 11

What are the leading and lagging strands?

Accepted Answer

DNA strands involved in DNA replication

The leading strand is replicated continuously in the same direction as the moving fork

The lagging strand is replicated discontinuously in the opposite direction, and made of Okazaki fragments

Question 12

What do 5' (5 prime) and 3' (3 prime) mean in DNA replication?

Accepted Answer

5' and 3' are carbon numbers in the DNA's sugar backbone

The 5' carbon has a phosphate group attached to it, while the 3' carbon has a hydroxyl group

Since the sides are asymmetric, the DNA strand has a "direction"

Question 13

What are Okazaki fragments?

Accepted Answer

Short sequences of DNA nucleotides that are linked together to form the lagging strand in DNA replication

(synthesized discontinuously; linked by DNA ligase)

Question 14

What is a mismatch repair?

Accepted Answer

A system for detecting and repairing issues in DNA

Removes the incorrect nucleotide and adds the proper one in its place

Question 15

What is excision repair?

Accepted Answer

Another repair mechanism in DNA replication that removes a section of DNA with errors, and fills the gap with DNA polymerase

Question 16

What is a genetic mutation?

Accepted Answer

An alteration in the nucleotide sequence of an organism's genome

(can help with genetic diversity, but usually leads to negative outcomes)

Question 17

What are point mutations?

Accepted Answer

Mutations that only affects a single nucleotide/base of nucleic acid

(deletion, insertion, substitution)

Question 18

What are frameshift mutations?

Accepted Answer

A type of mutation where some number of nucleotides are added or deleted, but only if that number isn't a multiple of three

(codons are given in triplets, which is why it can't be a multiple of three)

Question 19

What are missense mutations?

Accepted Answer

Type of mutation where the wrong nucleotides are substituted into the DNA sequence, resulting in the substitution of a different amino acid in the created protein

(could cause no problem, but can also lead to huge issues such as sickle cell anemia)

Question 20

What is a nonsense mutation (stop mutation)?

Accepted Answer

Type of mutation with substitution of the wrong nucleotides into the DNA sequence, causing a protein to stop being built earlier than expected

(the nonsense mutation causes a stop codon (which tells the protein synthesis when to stop) to be placed before the real stop codon)

Question 21

What are thymine dimers?

Accepted Answer

Damage caused by too much exposure to UV light, causing two adjacent thymine dimers to bind together

(can cause further mutations if the DNA tries to replicate)

Question 22

What happens to mRNA after being released from DNA, but before leaving the nucleus, in eukaryotes?

Accepted Answer

It is "touched up", with a guanine cap on the 5' end to protect it, and a polyadenine tail on the 3' end to help it move

(only happens in eukaryotes, not prokaryotes)

Question 23

What are introns and exons?

Accepted Answer

Introns are nucleotide sequences in RNA and DNA that do not directly code for proteins and are removed (intervening sequences)

Exons are nucleotide sequences in RNA and DNA that directly code for proteins (expressing sequences)

Question 24

What is RNA splicing?

Accepted Answer

A process where certain introns are cut out of the mRNA and the remaining exons are glued back together

(a bit strange that introns are not used, but there is a theory that cutting out different introns allow the organism to make different proteins from the same gene)

Question 25

What is gene regulation?

Accepted Answer

A mechanism for controlling which genes get expressed in cells, and at what levels

(in prokaryotes this can save huge amounts of energy by only creating the proteins required at the moment; in eukaryotes this allows for cell differentiation)

Question 26

What is a promoter?

Accepted Answer

A sequence of DNA that controls an operon, turning the operon's genes on/off

(usually found near the beginning of a gene; proteins bind to the promoter to initiate the transcription of RNA, which may encode for a protein)

Question 27

What are operons?

Accepted Answer

A cluster of genes under the control of a single promoter

(common in prokaryotes (bacteria), but very rare in eukaryotes (humans); all the genes function in the same process)

Question 28

What are regulatory DNA sequences?

Accepted Answer

DNA sequences that control the transcription of the operon

(also serve as binding sites for regulatory proteins, which control how much the operon is transcribed)

Question 29

What are repressors?

Accepted Answer

A type of regulatory protein that binds to operators, reducing transcription

(might block the RNA polymerase from moving forwards on the DNA)

Question 30

What are activators?

Accepted Answer

A type of regulatory protein that binds to the DNA binding site, increasing transcription of the operator

(might help the RNA polymerase bind to the promoter)

Question 31

What are operators?

Accepted Answer

A sequence of DNA that allows proteins responsible for transcription (into some type of RNA) to attach to a DNA sequence

(structural genes (code for synthesis of specific polypeptides) are connected with operators inside of the operon, and the operon as a whole can be turned on/off by the promoter)

Question 32

What are regulatory genes?

Accepted Answer

Genes that encode regulatory proteins

(e.g., a gene that codes for repressor proteins that inhibit transcription)

Question 33

What are regulatory proteins?

Accepted Answer

Proteins that control how much the operator is transcribed

Question 34

What are inducible and repressible operons?

Accepted Answer

Inducible operons are "off" by default, but can be turned "on" by a small molecule called an inducer (e.g., lac operon)

Repressible operons are "on" by default, but can be turned "off" by a small molecule called a corepressor (e.g., trp operon)

Question 35

What are housekeeping genes?

Accepted Answer

Genes that are constantly expressed because their products are needed by the cell to maintain essential functions

(opposite of genes that are regulated to only be expressed sometimes; housekeeping genes still have their own promoters and regulation to keep them active)

Question 36

What is the lac operon?

Accepted Answer

A famous inducible operon that is essential for transporting and metabolizing lactose in E.coli

(only turned on when the E.coli has lactose available but doesn't have glucose (it's preferred food))

Question 37

What is the trp operon?

Accepted Answer

A famous repressible operon that is responsible for making tryptophan (type of amino acid) in E.coli

(the trp repressor detects when there is already a lot of tryptophan in the cell, and tells the trp operon to stop making more)

Question 38

What is the purpose of gene regulation in eukaryotes?

Accepted Answer

Controls which cells of an organism are expressed so that different cells can perform different functions

Question 39

How do cells "decide" which genes to turn on?

Accepted Answer

Two main ways (although there are many others):

Internal Information: proteins it inherited from its mother cell, whether its DNA is damaged, and how much ATP it has

External Information: chemical signals from other cells, mechanical signals, and nutrient levels

Question 40

What are transcription factors?

Accepted Answer

Helper proteins that control the rate of genetic transcription

Turns genes "on/off" by binding to nearby DNA

Question 41

How do eukaryotic genes in an organism specialize in different functions?

Accepted Answer

They are regulated so that only produce proteins vital to their specific function

Question 42

What is a virus?

Accepted Answer

An infectious pathogen that can only replicate inside an organism's living cells

Question 43

Why are viruses dependent on their hosts?

Accepted Answer

They do not contain enzymes for metabolism nor ribosomes for protein synthesis, so they must rely on their host for these functions

(takes over its host cell's machinery and uses that to produce what it needs to survive)

Question 44

What is a capsid?

Accepted Answer

A protein shell that surrounds a virus, protecting the viral genome from the environment

Question 45

What is a viral envelope?

Accepted Answer

An outermost layer in many viruses that surrounds the capsid, both protecting the virus and also helping it to attach to cells it prefers to infect

(not all viruses have a viral envelope)

Question 46

What is a virus's host range?

Accepted Answer

The range of cells that the virus likes to infect

(HIV infects T cells; bacteriophages infect bacteria)

Question 47

What is a retrovirus?

Accepted Answer

Type of virus that inserts a copy of its RNA genome into the DNA of the host cell

(contains reverse transcriptase; HIV is a retrovirus)

Question 48

What is reverse transcriptase?

Accepted Answer

An enzyme that retroviruses use to "reverse transcribe" its RNA into DNA

The infected cell then uses this new DNA instead of its original DNA, causing it to create offspring for the virus

Question 49

What is lytic cycle?

Accepted Answer

One cycle of viral reproduction, where the infected cell produces many viral offspring and dies in the process of releasing them

(other cycle is the lysogenic cycle, which doesn't kill the cell immediately/directly)

Question 50

What is the lysogenic cycle?

Accepted Answer

One cycle of viral reproduction, where the infected cell incorporates its DNA into the infected cell's DNA, spreading itself each time the cell divides

(creates a provirus when its DNA is incorporated into the infected cell's; can sometimes enter the lytic cycle)

Question 51

What is a provirus?

Accepted Answer

A virus genome that is incorporated into the host cell's DNA

(created during the lysogenic cycle)

Question 52

What are viroids?

Accepted Answer

Small infectuous pathogens that infect plants

(incredibly small; only a few hundred nucleotides in length, with less than 10,000 atoms)

Question 53

What are prions?

Accepted Answer

Misfolded proteins that can convert normal proteins into other misfolded proteins

(mad cow disease is a prion)

Question 54

What is DNA transcription?

Accepted Answer

The process of copying a segment of DNA into mRNA, which then goes to a ribosome to create a certain protein

(mRNA=messenger RNA; DNA can't produce proteins by itself; carried out by RNA polymerase)

Question 55

Why does DNA need to be transcripted into mRNA?

Accepted Answer

DNA can't produce the proteins it encodes for by itself

It needs to be transcribed into mRNA (also built of nucleotides), which then tells ribosomes how to build a certain protein

Question 56

What is RNA polymerase?

Accepted Answer

An enzyme responsible for copying a DNA sequence into an RNA sequence during transcription

(attaches to a promoter region on a DNA strand (initiation), adds nucleotides to the 3' end of the growing strand (elongation), and stops when it reaches the termination site (termination))

Question 57

What is a promoter region?

Accepted Answer

A recognition site that RNA polymerase attaches to, starting initiation

(contains the TATA box)

Question 58

What is the TATA box?

Accepted Answer

A group of nucleotides in promoter regions that are important for binding the RNA polymerase

Question 59

How is the central dogma different in eukaryotes and prokaryotes?

Accepted Answer

Prokaryotes lack a nucleus, so they perform DNA replication, transcription, and RNA translation all at once

Eukaryotes have a nucleus, so while they also perform DNA replication and transcription, RNA must travel across the nuclear membrane before undergoing translation

Question 60

What are polyribosomes (polysomes)?

Accepted Answer

A group of ribosomes bound to an mRNA molecule that translate mRNA instructions into polypeptides

(similar to beads/threads; polypeptides=chains of amino acids)

Question 61

What are restriction enzymes?

Accepted Answer

Enzymes that cut out DNA at the specific nucleotide sequence that the enzyme contains

(creates "sticky-ends" which reconnect to other DNA fragments containing the same ends, with the ability to form recombinant DNA)

Question 62

What are sticky-ends?

Accepted Answer

Ends of DNA helixes where a few unpaired nucleotides extend a bit further beyond the other

(can be formed from restriction enzymes)

Question 63

What is recombinant DNA?

Accepted Answer

Artificially formed DNA that consists of genetic material from multiple sources

(scientists can make sticky-ends can merge (using ligase) with other sticky-ends containing the same ends, creating recombinant DNA)

Question 64

What is a vector, in genetics?

Accepted Answer

A DNA molecule that is used to artificially carry DNA from one source to another

Unit 6: Gene Expression and Regulation, AP Biology Flashcards