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Molecular Biology - Jourdan > Lecture 1 > Flashcards

Lecture 1 Flashcards

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0
Q

What was discovered in the late 19th century?

A

Hereditary information carried on chromosomes

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1
Q

What is a gene?

A

The information-containing elements that determine the characteristics of a species

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2
Q

When are chromosomes visible by light microscopy?

A

When the cell undergoes division

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3
Q

What do chromosomes contain?

A

DNA and protein

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4
Q

What are the building blocks of DNA?

A

Nucleic Acids

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5
Q

What are nucleotides joined together by?

A

Phosphodiester linkage between 5’ and 3’ carbon atoms

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6
Q

What do polynucleotides have?

A

Polarity, 5’ phosphoryl end, and 3’ hydroxyl end

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7
Q

What is the structure of DNA?

A

2 long polynucleotide chains with 4 types of nucleotide subunits
Nucleotides are 5 carbon sugar and nitrogenous base covalently linked via glycosidic bond
Sugar is deoxyribose
Adenine, cytosine, guanine, and thymine bases
Double Helix - 1 turn/10bp
Antiparallel

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8
Q

What are the purines in DNA?

A

Adenine and guanine

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9
Q

What are the pyrimidines in DNA?

A

Cytosine and thymine

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10
Q

What is a genome?

A

A complete set of information in an organism’s DNA

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11
Q

True or False?

At replication, the entire genome must be duplicated and passed to the daughter cell.

A

True

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12
Q

How many nucleotides does the human genome have?

A

3.2x10^9 nucleotides distributed over 24 different chromosomes

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13
Q

What is a chromosome?

A

Single long linear DNA molecular associated with proteins that fold and pack it into compact structure.

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14
Q

How many copies of each chromosome does the human cell have?

A

2 copies - maternal and paternal homologs-

Except germ cells and RBCs

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15
Q

How many pairs of autosomes are the in the human cell?

A

22 pairs

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16
Q

How many sex chromosomes does a human have?

A

2

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17
Q

What information is found on chromosomes?

A

Genes
-encoding proteins and RNA molecules
Interspersed DNA that does not contain genes
-regulatory information , junk DNA

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18
Q

How much of the average gene size comprise of coding region?

A

5%

19
Q

What is the percentage of DNA sequence in exons (protein coding sequences)?
Whole genome

A

1.5%

20
Q

What are functional sequences?

A

Sequences that are relatively conserved during evolution

21
Q

What are non-functional sequences?

A

Sequences that mutate randomly w/o consequence

22
Q

What are coding regions?

A

Exons that are typically 145 bp that are floating in a sea of large introns

23
Q

What is conserved synteny?

A

Large blocks of genes are conserved in the same order on the chromosome (compared to ancestors)

24
Q

What happens in interphase?

A

Chromosomes are replicated; they are decondensed and cant be easily distinguished

25
Q

What happens during mitosis?

A

Become highly condensed and separated into two daughter nuclei

26
Q

What are 3 important components of chromosomes?

A

DNA replication origin: where duplication of the DNA begins
Centromere: allows one copy of each duplicated and condensed chromosome to be pulled into each daughter cell
Telomeres: repetitive sequences at the end of a chromosome that enable the ends to be efficiently replicated

27
Q

What is chromatin?

A

Protein + nuclear DNA

28
Q

What is the most basic unit of chromosome packing?

A

nucleosome. Repeats after 200 nt

29
Q

How many histone proteins are in each individual nucleosomes core particle?

A

8 histones

30
Q

What are the 8 histones?

A

2 molecules each of H2A, H2B, H3, H4

31
Q

What is linker DNA?

A

Exposed DNA between nucleosome core particles

About 80 nt long

32
Q

What are histones?

A

Small proteins with common structural motif called histone fold.

33
Q

What bonds form between histones and DNA?

A

142 hydrogen bonds in each nucleosomes
Hydrophobic interactions
Salt linkages - lysine and arginine comprise more than 1/5 of histone residues, effectively neutralize negatively charged DNA backbone

34
Q

Are histones are conserved or non-conserved?

A

Highly conserved, most changes would e lethal

35
Q

True or False

Nucleosomes are static?

A

False,
It is in a dynamic situation to allow for rapid localized access to DNA for gene expression. Nucleosomes are in a constant state of flux

36
Q

What allows for a further loosening of DNA/histone contact?

A

Chromatin remolding complexes. Related to Helicase and are ATP dependent
Bind to both protein core and DNA

37
Q

What is the zig-zag model?

A

Theory how the nucleosome packs and becomes a dense fibrous.. Stacking that may be facilitated by histone tails and histone 1 is present in 1:1 ration with nucleosome cores

38
Q

What is the linker histone?

A

H1
Larger histone
Less well conserved

39
Q

What is needed to pack DNA?

A

Incredible amount of condensing. Mitotic chromosomes are condensed 500 x more than in interphase

40
Q

What are the DNA binding proteins involved in forming chromosomes?

A

Histones and non histones

41
Q

What forms beads on a string?

A

Chromatin isolated directly from interphase nucleus that is partially unfolded

42
Q

What breaks down DNA by cutting between Nucleosomes and degrading the exposed DNA (linker protein)

A

Nucleases

43
Q

What is the nucleosome core particle?

A

Disk shaped particle that DNA wraps 1.7 x around

44
Q

What are the tails of histones subject to?

A

N terminal a.a tail that extends out from the core are subject to covalent modifications important for chromatin regulation

45
Q

What adds to various chromosome structures?

A

Specialized variant histones

Molecular Biology - Jourdan (8 decks)

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