Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Alex's Genetics > Lecture 18a > Flashcards

Lecture 18a Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

There are at least 5 families of eukaryotic chromatin remodelers. Name the 5 families of chromatin remodelers in eukaryotics.

A
  1. SWI/SNF
  2. ISWI
  3. NuRD/Mi-2/CHD
  4. INO80
  5. SWR1
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

What do chromatin remodeling complexes do?

A

Either convert open euchromatin into closed heterochromatin or convert closed heterochromatin into open euchromatin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

What is an example of a SWI/SNF complex generating euchromatin?

A

There is a HO gene in yeast that allows for the conversion of genders from A to alpha or vice versa.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

Prior to the SWI/SNF complex, how does the HO coding sequence appear? Are the 2nd enhancer and core promoter able to be bound?

A

The HO sequence spends most of the time in repressive chromatin.

Neither the 2nd enhancer nor the core promoter can be bound while in repressive chromatin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

What separates the 5 families of chromatin remodelers in eukaryotes?

A

Each family shares similar proteins within them.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Explain the SWI/SNF complex steps for transforming genders.

A
  1. SWI5P binds to the enhancer upstream of the gene and recruits the SWI/SNF enzyme.
  2. SAGA is then recruited. Both the SAGA and SWI/SNF enzymes convert the heterochromatin to euchromatin in the promotor region.
  3. SBP binds to the enhancer element and recruits RNA polymerase and general transcription factors.
  4. Transcription takes place leading to a sex change.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the SWI/SNF complex?

A

An ATP-dependent remodeling enzyme that helps to remodel heterochromatin into euchromatin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is SAGA?

A

A histone acetyltransferase that acetylates the N-terminal tails of histones, turning heterochromatin into euchromatin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is SBP?

A

A second transcriptional activator, which binds to the SBP enhancer site and recruits RNA polymerase and general transcription factors to the core promotor.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Infectious particles have viral genomes. What 3 things can vary in viral genomes composition?

A
  1. DNA or RNA
  2. Single-stranded or double-stranded
  3. Circular or linear
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

T/F: Viral genome size is always the same.

A

False! Viral genome size and complexity is highly variable.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The smallest viruses consist of a few ______________ nucleotides and encode as few as __ proteins. Their genomes are as little as ___-kb of DNA or RNA.

A

thousand, 3, 3.5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Some of the largest viruses have genomes that are more than a ___________ nucleotides and encode ___________ proteins, and have more genes than some ______________.

A

million, >1000, bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do viral particles range in diameter/size?

A

They range from about 20 to 400 nm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

A typical bacteria is _____ nm in diameter.

Most eukaryotic cells have a diameter of ___ to ______ times that of a bacterium.

A

1000

10 to 1000

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Name the 2 groups of viral genomes.

A

Nonenveloped virus and enveloped viruses with spikes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are viruses?

A

Small infectious particles containing nucleic acid surrounded by a capsid or shell made up of proteins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are most nonenveloped viruses? What does this mean?

A

Most are lytic viruses, meaning that they destroy the cell when it leaves. They are “naked” so just surrounded by a capsid. However, there are some nonenveloped viruses that are not lytic.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What do viruses rely on for replication?

A

For replication, viruses rely on the cells that they infect aka their host cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe enveloped viruses.

A

Enveloped viruses get their membrane from wrapping a previous infected cell around it. Most enveloped viruses bud out of the cell (spike proteins) when it leaves, but a few are lytic.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

A virus binds a ________ in the cell surface and then ________ its genome into the cell.

A

protein, injects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are spike proteins?

A

Viral proteins in the membrane that surrounds the virus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

The viral ___________ is replicated in the cells and viral _______ are used to make viral ________.

A

genome, genes, proteins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe the process of how a virus gets into a cell.

A

1) A virus only binds to cells with the right receptor on them.
2) This viral binding leads to membrane fusion (in enveloped viruses).
3) The viral genome (DNA or RNA depending on the virus) is then injected/released into the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Most viruses exhibit a limited ___________, meaning that they only infect specific types of cells of one host species.

A

host range.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does host range mean?

A

The species and cell type that the virus can infect.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is an example of a virus that has limited host range?

A

The AIDS virus encodes a protein called gp120 which interacts with the CD4 proteins (T cells) on a subset of white blood cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is an example of an enveloped virus with a wide host range? How does transmission of this virus occur?

A

The rabies virus can recognize 1 of 3 proteins and bind to one. Transmission occurs via saliva.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

If individuals who are not vaccinated against it acquire rabies, what happens?

A

It is the most deadly virus known to infect humans, so it is nearly 100% lethal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Does the rabies vaccine work?

A

Yes, it even works for someone who is vaccinated shortly after being bitten by a rabid animal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are the 3 proteins the rabies virus can recognize in muscle and neurons?

A

nAChR, NCAM, and p75NTR.

It only needs to recognize 1 of the 3.

28
Q

Describe the process of producing an enveloped virus.

A

1) As the viral capsid approaches the membrane from inside, viral glycoproteins are expressed to help the membrane wrap around the capsid.
2) Cross-section of the host cytoplasmic membrane occurs.
3) Then, budding of the enveloped virus occurs.
4) The enveloped virion is released.

29
Q

Generally speaking, how are enveloped viruses released?

A

By viral budding

30
Q

T/F: Non-enveloped viruses have 1 method to lyse the infected cells.

A

False! Non-enveloped viruses use a variety of mechanisms to lyse (bust open) the infected cells to release infectious particles.

31
Q

What occurs in an infected cell? How does the virus move to the next cell?

A

The viral protein and DNA are synthesized in the infected bacterial cell. Then, genes are expressed that rupture the cell and infectious viruses are released.

32
Q

Name the 3 types of mutations.

A

1) Changes in chromosome structure.
2) Changes in chromosome number.
3) Single-gene mutations

33
Q

What are single-gene mutations?

A

Relatively small changes in DNA structure that occur within a particular gene.

34
Q

What do changes in chromosome structure impact?

A

Gene expression

35
Q

What are 2 ways in which chromosome structure impacts gene expression?

A

1) A chromosomal rearrangement may affect a gene because the break occurred in the gene itself.
2) A gene can be intact but its expression can be altered from moving to a new location.

36
Q

What is the Position Effect?

A

A gene moves to a new location and can now be over-expressed, expressed where it isn’t supposed to be, or silenced.

37
Q

What are 2 common reasons for the Position Effect?

A

1) Movement to a position next to regulatory sequences. The promotor of a one gene may influence both/all genes now.
2) Movement to a position in a heterochromatic region. The gene will now be silenced.

38
Q

What is a point mutation?

A

A change in a single base pair; it involves a base substitution (not an insertion or deletion).

39
Q

Name the 3 types of point mutations.

A

1) Silent mutations
2) Missense mutations
3) Nonsense mutations

40
Q

What is a silent mutation?

A

When there is a base substitution in a translated gene sequence but this does NOT alter the amino acid sequence of the polypeptide.

41
Q

Why do silent mutations not alter the amino acid sequence of the polypeptide?

A

Due to the degeneracy of the genetic code, meaning that there is more than one codon per amino acid.

42
Q

What is a missense mutation?

A

When there is a base substitution that changes the amino acid.

43
Q

In a nonsense mutation, what does neutral mean? How does this occur?

A

If the substituted amino acid has no detectable effect on protein function, the mutation is NEUTRAL.

This occurs because the new amino acid has similar chemistry.

44
Q

What is a nonsense mutation? What does this result in?

A

When there is a base substitution that changes a normal codon to a termination/stop codon. This results in a shorter amino acid chain.

45
Q

How does the product differ when a nonsense mutation is early in the sequence versus late in the sequence?

A

Early in sequence = null allele

Later in sequence = not so bad

46
Q

What does Deleterious mean?

A

The mutation is bad for/screws up the organism.

47
Q

What are Frameshift Mutations? What does this result in?

A

This involves the addition or deletion of nucleotides that shift the reading frame. This results in a completely different amino acid sequence that occurs downstream from the mutation.

48
Q

What is a Spontaneous Mutation?

A

Mutations that result from errors in cellular/biological processes, often errors in DNA replication.

49
Q

T/F: Normal cellular processes never produce chemicals that are mutagenic.

A

False! Some normal cellular processes produce chemicals that are mutagenic (ex: free radicals). These are spontaneous mutations.

50
Q

What are Induced Mutations?

A

Mutations caused by environmental agents (ex: Needing an x-ray image from an injury).

51
Q

What are Mutagens? Name the 2 types.

A

Agents (outside of cell) that are known to alter DNA structure. There are chemical and physical mutagens.

52
Q

What are Physical Mutagens?

A

All photons that are powerful enough to cause damage including Ionizing radiation and Non-ionizing radiation.

53
Q

What are 3 examples of Ionizing Radiation? How does radiation differ between people?

A

X-rays, gamma rays, subatomic particles. The amount of radioactivity varies based on your location.

54
Q

What is Non-Ionizing Radiation?

A

Mainly UV/Visible light.

55
Q

Name the 3 types of Chemical Mutagens.

A

Base modifiers, intercalating agents, and base analogues.

56
Q

What do Base Modifiers do?

A

Modify the bases of nucleotides.

57
Q

What are Intercalating Agents?

A

Flat chemicals that slide between bases in DNA and cause bad replication.

58
Q

What are Base Analogues?

A

Bases that look similar to normal bases will end up producing unwanted nucleotides.

59
Q

Why are DNA repair systems critical for survival of all organisms?

A

Most mutations are deleterious (bad).

60
Q

The repair systems sometimes _________ with each other to repair DNA damage.

A

compete

61
Q

What does Nucleotide Excision Repair (NER) do?

A

This is a system that removes damaged DNA segments.

62
Q

In _________, the NER system requires ____ key proteins. Name them.

A

E. coli, 4

UvrA, UvrB, UvrC, and UvrD.

63
Q

Where does the name for the NER system proteins come from?

A

They are involved in UltraViolet light Repair (UVR) of pyridine dimers. They are also important in repairing chemically damaged DNA.

64
Q

Explain how Nucleotide Excision Repair (NER) removes damaged DNA segments.

A
  1. The UvrA/UvrB complex scans along DNA to find damage.
  2. After damage is detected, UvrA is released and UvrC binds.
  3. UvrC makes cuts on both sides of the thymine dimer.
  4. UvrD removes the damaged region while UvrB and UvrC are released.
  5. DNA polymerase makes the single-strands double-stranded and DNA ligase seals the region.
65
Q

What is a Thymine Dimer?

A

When there are 2 covalent bonds between adjacent Thymines on the same strand.

66
Q

Generally speaking, what is UvrD?

A

A helicase that uses ATP to remove damaged DNA.

67
Q

Describe the cuts that UvrC makes.

A

Typically, the cuts are 4-5 nucleotides from the 3’ end of the damage, and 8 nucleotides from the 5’ end.

68
Q

What does “Repair of Actively Transcribed DNA” mean?

A

This means we working on repairing regions of DNA where there are genes instead of non-gene regions.

69
Q

What is a Transcription-Repair Coupling Factor (TRCF)?

A

In E. coli, this is a protein that targets the NER system to fix damaged DNA that are actively transcribing gene-regions.

70
Q

T/F: Humans have Transcription-Repair Coupling Factor (TRCF).

A

False!

71
Q

Describe how Transcription-Repair Coupling Factor (TRCF) works.

A

1) RNA polymerase moves along until it acquires a thymine dimer causing it to stop.
2) TRCF removes the RNA polymerase from the damaged region and recruits the UvrA/UvrB complex.
3) TRCF is then released.
4) The region is repaired as describe in nucleotide excision.

72
Q

Generally speaking, what is TRCF? What type of binding site does it have?

A

A helicase.

It has a UvrA binding site for the UvrA/UvrB complex.

Alex's Genetics (38 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions