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Genetics > Genetics Chapter 12 > Flashcards

Genetics Chapter 12 Flashcards

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Biology 101 flashcards
1
Q

Origin of replication for Eukaryotes

A

linear DNA, multiple origins of replication

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2
Q

Origin of replication for Prokaryotes

A

circular DNA with 1 origin of replication

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3
Q

Transcription location for both eukaryotic and prokaryotic

A

Prokaryotes: cytosol
Eukaryotes: nucleus

Both eukaryotic and prokaryotic DNA polymerases build off RNA primers made by primase

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4
Q

Chromosomes

A

contain genetic material

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5
Q

Genome

A

genetic material

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6
Q

Chromatin

A

packaging of DNA and histones (DNA protein complex)

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7
Q

Bacterial Chromosomes Structure

A
  • Circular molecule in cytosol
  • 1 Origin of replication
  • DNA segments between genes: intergenic regions
  • Bacterial genes are often found in operons
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8
Q

Operons

A

group of genes that function as SINGLE UNIT controlled by ONE promotor

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9
Q

Bacterial Genome Compaction

A

Nucleoid-associated proteins (NAPs) form the micro and macrodomains
Bend DNA or act as bridges between DNA regions

Histone-like nucleoid structures (H-NS)

Structural maintenance of chromosomes (SMC)

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10
Q

Eukaryotic Chromosomes Structure

A

Linear chromosome in nucleus

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11
Q

Eukaryotic Genes

A
  • Genes in between the centromeric and telomeric
  • Yeast: small genes + few introns
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12
Q

DNA Supercoiling

A
  • Both underwinding and overwinding of the DNA double helix can induce supercoiling
  • DNA structures that differ in supercoiling are called topoisomers of each other
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13
Q

DNA Supercoiling Affects Chromosome Function

A

In E. coli, there is one negative supercoil per 40 turns of the double helix

Helps in the compaction of the chromosome

Creates tension that may be made by DNA strand separation

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14
Q

Control of Supercoiling

A

DNA gyrase (a.k.a. topoisomerase II)

DNA topoisomerase I

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15
Q

DNA gyrase (a.k.a. topoisomerase II)

A

Creates negative supercoils using energy from ATP

Can also relax positive supercoils when they occur

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16
Q

DNA topoisomerase I

A

Relaxes negative supercoils

Breaks one strand and rotates the DNA

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17
Q

Supercoiling Enzymes as Drug Targets

Two main classes of drugs inhibit bacterial topoisomerases, but do not inhibit eukaryotic ones

A

Quinolones
- ciprofloxacin (“Cipro”)
- quinine

Coumarins

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18
Q

Negative supercoiling

A

supercoils from LEFT (underwinds)

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19
Q

Positive supercoiling

A

right hand turn (overwinding)

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20
Q

When helicase unwinds the DNA, it creates tension at the replication fork (where the strands separate). This tension is known as

A

supercoiling- relieved by Topoisomerase

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21
Q

Discuss the various roles of supercoiling and why cells need to be able to do it.

A

Genetic diversity
Replication
DNA strand separation

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22
Q

Telomeres

A

contains many copies of DNA sequences at the end of the chromosomes

This will protect the genome from degradation

Preserves information

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23
Q

Genome complexity

A

Genome complexity is not correlated with organismal complexity
Variation is not necessarily related to complexity

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24
Q

Sequence Complexity

A

Refers to the number of times a particular DNA sequence appears in the genome

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25
Q

Unique or non-repetitive sequences

A

structural genes + introns and other noncoding DNA

26
Q

Moderately repetitive

A

Includes rRNA and transposable elements

27
Q

Highly repetitive

A

Some are transposable elements (Alu elements)

Others are clustered together in tandem arrays

28
Q

telomerase in normal cells

A

Telomeres shorten every cell division as we age
Normal telomeres allow for cell division and tissue generation

29
Q

telomerase in cancer cells

A

Cancer cells maintain their telomeres despite undergoing repeated cell divisions
Cancer cells activates telomerase→adding genetic units onto the telomeres to PREVENT them from shortening

30
Q

Describe the location, composition, and function of telomeres and centromeres

A

Centromeres binds two sister chromatids

Telomeres are repetitive sequences of nucleotides at the end of chromosomes

Centromeres are made up of repeated DNA

31
Q

Nucleosomes

A

Nucleosomes are octamers of histone proteins + DNA

Nucleosomes join to Form a 30-nm Fiber which shortens the total length of DNA 7-fold

32
Q

Histone N-terminal tails

A

Histone N-terminal tails modulates the structure and function

H2A,H2B,H3 and H4 are the core histones (2 of each)

H1 is the linker histone

33
Q

Histone Proteins

A

DNA is wrapped around histones

34
Q

Chromosome compaction

A

increases during cell division

35
Q

Histone tails are modified

A

Modifications are correlated with heterochromatin or euchromatin

36
Q

Acetylation: adding acetyl groups

A

histones remove positive charges→relaxing DNA-histone attraction→ allowing for MORE TRANSCRIPTION→EUCHROMATIN

37
Q

Methylation: adds methyl groups

A

either increasing or decreasing transcription

DNA methylation suppress gene transcription—>heterochromatin

38
Q

Euchromatin

A
  • Less condensed, transcriptionally active

Chromatin is LOOSELY bound to nucleosomes

Present when DNA is ACTIVELY TRANSCRIBE

LIGHTER

“You actively LIGHTER/loose”

39
Q

Heterochromatin

A

Tightly and transcriptionally inactive

TIGHTLY PACKED NUCLEOSOMES
DNA is inactive
DARKER
Found: telomeres & centromeres

40
Q

Nuclear matrix: ….

composed of two parts

A

creates higher order structure and compacts DNA into radial loop domains

Nuclear lamina — fibers lining the inner membrane

Internal nuclear matrix — connects to lamina, fills nucleus interior

41
Q

Radial Loop Domains

A

Matrix-attachment regions (MARs) also known as Scaffold-attachment regions (SARs) are DNA sequences interspersed in the genome

They anchor to the nuclear matrix, forming radial loops

42
Q

Transposition

A

integration of transposable elements (TEs) of DNA into the chromosome

“jumping genes”

43
Q

Simple Transposition

A

“cut and paste” mechanism
aka transposons
increases TE number during DNA replication

44
Q

Insertion Elements (IS element)

A

The simplest type of TE
Both ends have inverted repeats (IRs)
Contains the transposase gene

45
Q

What is required for transposition?

A

Transposase (enzyme) and Indirect repeats

46
Q

Transposase

A

removes and reinserts

47
Q

Autonomous TEs

A

Autonomous TEs contain all the information necessary for transposition to occur

48
Q

Nonautonomous TEs

A

Nonautonomous TEs lack a gene that is necessary for transposition to occur

49
Q

Retrotransposition

A

TE is transcribed into RNA, then reverse transcriptase makes DNA copy that is inserted in the genome

retrotransposons or retroelements

50
Q

The steps of transposition and retrotransposition

A

Step 1: transposase is made from the transposable elements

Step 2: transposase monomers bind IRs

Step 3: transposase dimerizes bringing IRs together

Step 4: DNA is cleaved between Drs and IRs, releasing the TE comes from the chromosome

Step 5: TE is reinserted in a new location

51
Q

All TEs are

A

All TEs are flanked by direct repeats (DRs), also called target-site duplications
These direct repeat sequences go in the same direction on both sides

52
Q

Where do TEs insert in the genome?

A

When TEs excise from the genome, they leave behind a DR “scar”

Target sequences depend on the TE family

TEs prefer AT-rich sequences

TEs make up a significant portion of the genome

53
Q

LTR(long terminal repeats) Retrotransposons

A

Related to retroviruses, but cannot make viral particles

Contain long terminal repeats (LTRs) at both ends

Encode reverse transcriptase and integrase

54
Q

Non-LTR Retrotransposons

A

Less like retroviruses

May encode reverse transcriptase /endonuclease

Some derived from normal eukaryotic genes

Ex: Alu in humans

55
Q

The significance of direct repeats flanking transposable elements and how they are made.

A

Flanking of direct repeats play an important role in the insertions of transposable elements (TE)

After TE are removed, these repeats are left behind as footprints

Footprints can alter gene expression

56
Q

P elements in Drosophila can cause

A

sterility

P elements are a TE that was found in natural populations of Drosophila but not in the laboratory strains

57
Q

Biological Significance of TEs?

A

Selfish DNA hypothesis

TEs exist because they can

Like parasites, can proliferate in host as long as they do not overly harm the host

TEs offer an advantage

In bacterial, may carry antibiotic-resistance genes

May cause insertion of exons into the coding region of other genes, providing new functions – exon shuffling

58
Q

Negative Effects of TEs

A

Insertions can cause mutations

Excisions can cause chromosome breaks and rearrangements

When transposon activity is not regulated and kept under control, they can cause chromosomal abnormalities and sterility

59
Q

In a bacterium, the region of the cytoplasm where the compacted chromosome is located is called the

A

nucleoid

60
Q

What is a nucleoid?

A

A region in a bacterial cell where the compacted chromosome is located.

Genetics (5 decks)

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