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5 Flashcards

1
Q

What are the three main components of a nucleotide?

A
  1. A pentose sugar
  2. A phosphate group
  3. Nitrogenous base
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2
Q

What is complementary base pairing in DNA?

A

In DNA, adenine (A) pairs with thymine (T) via two hydrogen bonds - and guanine (G) pairs with cytosine (C) via three hydrogen bonds

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3
Q

What type of bond holds the two strands of DNA together?

A

Hydrogen bonds between complementary nitrogenous bases

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4
Q

What is the significance of DNA being antiparallel?

A

The two DNA strands run in opposite directions, meaning one strand runs 5’ to 3’ and the complementary strand runs 3’ to 5’

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5
Q

What is the sugar-phosphate backbone in DNA?

A

The sugar-phosphate backbone is the repeating structure of sugar (deoxyribose) and phosphate that forms the outer structure of DNA, with the nitrogenous bases pointing inward

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6
Q

What is a chromosome?

A

a long strand of DNA tightly packed with proteins, mainly histones, that carry genetic information

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7
Q

What is chromatin?

A

Chromatin is the material that makes up chromosomes, consisting of DNA and histone proteins

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8
Q

What is the role of histones in DNA packaging?

A

Histones are proteins around which DNA wraps to form nucleosomes, the basic units of chromatin structure, aiding in DNA condensation and accessibility

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9
Q

What is a nucleosome?

A

A nucleosome is a structural unit of chromatin, consisting of DNA wrapped around a core of eight histone proteins

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10
Q

How do histones and DNA interact?

A

DNA, which is negatively charged due to its phosphate groups, wraps around positively charged histones, which contain basic amino acids like lysine and arginine

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11
Q

What is the first level of DNA packaging in eukaryotic chromosomes?

A

DNA wraps around histone proteins to form nucleosomes, which are the first level of packaging

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12
Q

What is the 30 nm fiber in chromosome structure?

A

The 30 nm fiber is a further condensed form of chromatin, where nucleosomes are packed together with the help of histone H1

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13
Q

How is chromatin made dynamic to allow replication and transcription?

A

Chromatin is made dynamic through chromatin remodeling complexes and histone modifications, such as acetylation, which loosen or tighten the chromatin structure

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14
Q

What is the role of histone acetylation?

A

Acetylation of histone tails neutralizes the positive charge, loosening the interaction between histones and DNA, thus making the chromatin more accessible for transcription

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15
Q

What are the key structural components of a eukaryotic chromosome that ensure its replication and separation?

A

The telomere (protects the ends of chromosomes and allows for complete replication), the replication origin (where replication begins), and the centromere (attaches to mitotic spindles during cell division)

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16
Q

What is the function of the nuclear membrane?

A

The nuclear membrane (or nuclear envelope) consists of two concentric membranes that separate the nucleus from the cytoplasm and contains nuclear pores for selective transport

17
Q

What is the function of the nucleolus?

A

The nucleolus is the site of ribosomal RNA (rRNA) synthesis and the assembly of ribosomal subunits

18
Q

What is the difference between interphase and M-phase chromosomes?

A

Interphase chromosomes are less condensed and allow for gene expression and replication, while M-phase chromosomes are highly condensed to facilitate segregation during cell division

19
Q

What is the genome?

A

The genome is the complete set of genetic information in an organism’s DNA

20
Q

What causes the uniform diameter of the DNA double helix?

A

The pairing of purines (adenine and guanine) with pyrimidines (thymine and cytosine) ensures a uniform diameter, with A pairing with T and G pairing with C

21
Q

What role do nuclear pores play in the cell?

A

Nuclear pores act as selective channels that regulate the movement of molecules, such as RNA and proteins, between the nucleus and the cytoplasm

22
Q

How long is the total length of DNA in a single human cell?

A

Approximately 2 meters of DNA are packed into each human cell

23
Q

What is the challenge related to packaging DNA into chromosomes?

A

The challenge is to compact the 2 meters of DNA into a nucleus that is only about 5 µm in diameter, while still maintaining accessibility for replication and transcription

24
Q

How do chromatin remodeling complexes affect DNA packaging?

A

Chromatin remodeling complexes reposition or restructure nucleosomes to allow greater accessibility to DNA, facilitating processes like replication and transcription

25
Q

What is the significance of telomeres on chromosomes?

A

Telomeres protect the ends of chromosomes from degradation and ensure that the entire length of the chromosome is replicated

26
Q

What is the role of centromeres during cell division?

A

Centromeres are DNA sequences that allow chromosomes to attach to mitotic spindles during cell division, ensuring proper chromosome segregation

27
Q

What is chromatin made of?

A

Chromatin consists of DNA and proteins, primarily histones, which help in the compaction and organization of DNA within the nucleus

28
Q

What happens during histone deacetylation?

A

Histone deacetylation removes acetyl groups from histones, restoring their positive charge, which leads to tighter chromatin packing and inhibits transcription

29
Q

Why do purines always pair with pyrimidines in DNA?

A

Purines (adenine and guanine) are larger, two-ring structures, while pyrimidines (thymine and cytosine) are smaller, single-ring structures. Pairing them maintains the uniform diameter of the DNA double helix

30
Q

Why is DNA packaging dynamic, and why is this important for the cell?

A

DNA packaging must be dynamic to allow for gene expression, replication, and repair, which require access to specific regions of the DNA at different times

31
Q

What is the function of histone H1?

A

Histone H1 helps pull nucleosomes together, forming a more condensed 30 nm fiber, which is an important step in chromatin packaging

32
Q

How many histone proteins make up the core of a nucleosome?

A

The nucleosome core consists of 8 histone proteins (2 copies each of H2A, H2B, H3, and H4)

33
Q

What happens to chromosomes during the M-phase of the cell cycle?

A

Chromosomes become highly condensed to ensure accurate segregation during mitosis

CB (13 decks)

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