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Molecular Biology > Lecture 1-2: DNA, Chromosomes and Genomes > Flashcards

Lecture 1-2: DNA, Chromosomes and Genomes Flashcards

1
Q

Examples of Epigenetics (3)

A

DNA methylation Chromatin structure Histone modification

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2
Q

ATP-dependent chromatin remodeling protein is located where

A

On reader writer complex. Uses ATP to either condense or decondense long stretches of chromatin

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3
Q

Chromatin consists of

A

Nuclear DNA + Protein

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4
Q

Purifying Selection

A

Elimination of mutations that interfere with important genetic functions

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5
Q

Phosphorylation of serine (covalent modification)

A

Gene activates

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6
Q

SNPs

A

Single nucleotide polymorphism Points in genome where one group has one nucleotide and another group has another

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7
Q

Acetylation of lysines (covalent modification)

A

Loosens chromatin structure (added by histone acetyl transferases, removed by histone deacetylase complexes)

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8
Q

Duplication and divergence

A

Both copies of gene maintain functional while diverging in sequence and pattern of expression

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9
Q

Pseudogenes

A

A duplicated gene that has become irreversibly inactivated by mutations

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10
Q

HS4 region

A

Contains cluster of histone acetylase binding sites, protects beta-globulin locus from silencing

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11
Q

Nucleosome consists of

A

8 histone proteins (histone octamer) DS-DNA that is 147 nucleotide pairs long

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12
Q

Condensation of chromosomes function

A

Disentanglement of sister chromatids Protection of fragile DNA molecule as separation occurs

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13
Q

Epigenetics

A

A form of inheritance that is superimposed on the genetic inheritance based on DNA

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14
Q

Interactions between DNA and histone

A

H-bonds Hydrophobic interactions Salt linkages (1/5 of histone residues are lysine or argenine +)

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15
Q

Barrier sequence function

A

Halt the spread of chromatin modifications

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16
Q

Chromatin remodeling complex

A

Allow further loosening of DNA/histone contact Changes structure of DNA temporarily, making DNA less tightly bound

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17
Q

Zone of inactivation

A

Area around heterochromatin, can spread different distances in different cells

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18
Q

DNA condensation is a ____ situation

A

Dynamic

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19
Q

Nucleosome

A

Most basic unit of chromosome packing

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20
Q

Final level in chromosome packing is during

A

Mitosis, very condensed

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21
Q

of hydrogen bonds formed between histone core and DNA in each nucleosome

A

142 H-bonds

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22
Q

Chromosome requirements (3)

A

DNA replication origin Centromeres Telomeres

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23
Q

Nucleotides are made of

A

5-carbon sugar and nitrogenous base covalently linked via glycosidic bond

24
Q

Chromosomes during interphase:

A

Chromosomes are replicated; they are decondensed and difficult to distinguish

25
Q

Position effect variegation

A

Breakage events that bring heterochromatin near active genes tends to silence them

26
Q

Position effect

A

Activity of a gene depends on position on the chromosome

27
Q

Lysine methylation (covalent modification)

A

Silences genes (added by methyl transferases, removed by demethylases)

28
Q

Histone code read by

A

Code reader complex Involves joint recognition of histone tail and covalent modification

29
Q

Nucleosome packing

A

Forms dense fibrous structure with diameter of 30nm

30
Q

Heterochromatin is very concentrated near

A

Telomeres and centromeres

31
Q

Histone code determines

A

Determines how/when DNA is packaged in nucleosome

32
Q

Histone H1

A

Linker histone Contacts both DNA and protein Changes path of DNA as it exits nucleosome

33
Q

Heterochromatin location in nucleus

A

Usually associates with nuclear lamina

34
Q

Types of barrier sequences

A

Physical barriers Enzymatic barriers

35
Q

8 Histone proteins include

A

2 molecules each of H2A, H2B, H3, H4

36
Q

How can various possible chromatin structures arise

A

Specialized variant histones

37
Q

Centromeric sequences

A

Consist of short repetitive DNA sequences called alpha satellite DNA Defined by assembly of proteins (i.e., H3 histone), not DNA sequence Centromeres can form spontaneously w/o alpha satellite DNA sequence

38
Q

Interphase chromosome structure

A

Lampbrush- series of large chromatin loops emanating from a linear chromosome axis

39
Q

Translocation of chromosome 9&22 form

A

Philadelphia chromosome on chromosome 22. Commonly found in CML

40
Q

Homologues

A

Genes that are similar in both sequence and function due to common ancestry

41
Q

Building blocks of DNA

A

Nucleic acids

42
Q

How are different activities localized in the nucleus

A

Different neighborhoods have effects on gene expression.

43
Q

Nucleotides are joined together via

A

Phosphodiester linkage between 5’ and 3’ carbon atoms

44
Q

CNVs

A

Copy number variants Presence of many duplications and deletions of large blocks of DNA

45
Q

Chromosomes during mitosis

A

Chromosomes are highly condensed and separated into two daughter nuclei

46
Q

Histone tails

A

Help to condense chromatin Largely unstructured, highly flexible Can form interactions with adjacent nucleosomes

47
Q

Heterochromatin

A

Very condensed chromatin, stains darkly throughout the cell cycle, even interphase

48
Q

Condensins

A

Use ATP hydrolysis to coil DNA molecules into chromatids

49
Q

Major histones are synthesized and assembled when

A

Synthesized during S-phase Assembled into nucleosomes on daughter DNA helices just behind replication fork

50
Q

Code reader-writer complex

A

Reads modifications and spreads them to nearby nucleosomes

51
Q

Percentage of DNA sequence in exons

52
Q

Nucleosomes repeat every _#_ nucleotides

A

~200 nucleotides between

53
Q

Varient histones synthesized and inserted when

A

Synthesized during interphase Inserted into already-fromed chromatin, REQUIRES histone exchange process catalyzed by chromatin remodeling complex

54
Q

How do genomic changes occur

A

Mistakes in DNA replication and repair Movement of transposable elements

55
Q

Reasons for sequence conservation

A

Not having enough time for mutations to occur since lineages separted Purifying selection

Molecular Biology (25 decks)

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