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Bio 101-Lecture Test 3 Flashcards

1
Q

Who discovered that DNA is the genetic material?

A

Griffith, Avery, MacLeod, McCarty, Hershey, and Chase

Each of these scientists conducted pivotal experiments leading to the understanding of DNA as the genetic material.

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2
Q

What did Griffith’s experiment demonstrate?

A

An ‘unknown substance’ transformed non-pathogenic bacteria into pathogenic bacteria

This ‘unknown substance’ was later identified as DNA.

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3
Q

What did Avery, MacLeod, and McCarty conclude from their experiments?

A

DNA was the ‘unknown substance’ that transformed non-pathogenic bacteria into pathogenic bacteria

They separated components of heat-killed bacteria and found only DNA could cause transformation.

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4
Q

What was the significance of the Hershey and Chase experiment?

A

Showed that DNA, not proteins, contains genetic information

They used radioactive labeling to trace which molecule entered bacterial cells.

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5
Q

What does Chargaff’s rule state?

A

In one DNA molecule, there will be equal proportions of adenine (A) and thymine (T), and equal proportions of cytosine (C) and guanine (G)

This pairing is due to the predictable hydrogen bonding between the bases.

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6
Q

What are the three components of a DNA nucleotide?

A

Phosphate, five-carbon sugar (ribose or deoxyribose), and a nitrogenous base (A, C, T, G)

These components are essential for forming the DNA structure.

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7
Q

Describe the structure of DNA.

A

DNA is a double helix with a sugar-phosphate backbone and nitrogenous bases on the inside

The two strands are complementary and held together by hydrogen bonds.

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8
Q

What are purines and pyrimidines in DNA?

A

Purines: A and G; Pyrimidines: C and T

Purines are larger with two fused rings, while pyrimidines are smaller with one ring.

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9
Q

What is the directionality of DNA strands?

A

DNA has a 5’ end and a 3’ end

This is based on the orientation of the carbon atoms in the sugar molecule.

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10
Q

What is the central dogma of molecular biology?

A

DNA -> mRNA -> protein

This describes the flow of genetic information within a biological system.

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11
Q

How does RNA differ from DNA structurally?

A

RNA is single-stranded, uses ribose, and has uracil (U) instead of thymine (T)

RNA has multiple functions beyond just carrying genetic information.

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12
Q

List the different types of RNA and their functions.

A
  • Messenger RNA (mRNA) – transports DNA’s message to ribosome
  • Transfer RNA (tRNA) – brings amino acids to ribosome
  • Ribosomal RNA (rRNA) – component of the ribosome

Other types include microRNA (miRNA) involved in gene expression regulation.

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13
Q

What are the phases of transcription?

A
  • Initiation
  • Elongation
  • Termination

Transcription converts DNA into mRNA in the nucleus.

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14
Q

What are the features of post-transcriptional modifications in eukaryotes?

A
  • 5’ cap added
  • PolyA tail added
  • Introns spliced out, exons spliced together

These modifications are essential for mRNA stability and translation.

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15
Q

What is a codon?

A

A triplet of nucleotides that codes for one amino acid

Codons are read sequentially during translation without skipping or overlapping.

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16
Q

Describe the structure of tRNA.

A

tRNA has an anticodon at one end and carries an amino acid at the other end

It functions as an interpreter during translation.

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17
Q

What are the components required for translation?

A
  • Ribosome
  • mRNA
  • tRNA
  • Amino acids

Each component plays a crucial role in synthesizing proteins.

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18
Q

What are the phases of translation?

A
  • Initiation
  • Elongation
  • Termination

Translation occurs on ribosomes and involves the assembly of amino acids into a polypeptide chain.

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19
Q

Define gene expression.

A

The process of using a gene’s information to make proteins

Not all genes are expressed at all times in a cell.

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20
Q

What is gene control?

A

Mechanisms that regulate which proteins are made and when

This includes pre-transcriptional, post-transcriptional, and post-translational controls.

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21
Q

What is an operon?

A

A cluster of genes under control of a single promoter in prokaryotes

The lac operon is a classic example of gene regulation.

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22
Q

What are the levels of gene control in eukaryotic cells?

A
  • Pre-transcriptional
  • Post-transcriptional
  • Post-translational

Each level provides a mechanism for regulating gene expression.

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23
Q

Define mutation.

A

A change in an organism’s DNA sequence

Mutations can be caused by errors during replication, radiation, or environmental factors.

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24
Q

What are the types of point mutations?

A
  • Silent mutation
  • Missense mutation
  • Nonsense mutation

Each type has different effects on protein function.

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25
What is a frameshift mutation?
A mutation caused by insertion or deletion that shifts the reading frame ## Footnote This usually results in a nonfunctional protein.
26
Describe the process of DNA replication.
Synthesis of an identical DNA molecule involving multiple enzymes ## Footnote Key enzymes include DNA helicase, DNA polymerase, and DNA ligase.
27
What is semiconservative replication?
Each new DNA molecule contains one parent strand and one daughter strand ## Footnote This model was confirmed by experiments demonstrating the nature of DNA replication.
28
How do prokaryotic cells divide?
By binary fission ## Footnote This is a simpler form of cell division compared to eukaryotic mitosis.
29
What are the different products of DNA replication and RNA transcription?
Two identical DNA molecules vs one original DNA molecule and one mRNA transcript
30
What is the key difference in the use of the template during DNA replication and RNA transcription?
DNA replication uses both strands, while RNA transcription uses only 1 template strand
31
What do DNA polymerase and RNA polymerase have in common?
Both synthesize nucleic acids in the same direction (read from 3’ to 5’, synthesize from 5’ to 3’)
32
What is the process by which prokaryotic cells divide?
Binary fission
33
How do eukaryotic cells divide?
Mitosis and meiosis
34
What protein helps package and organize DNA in a chromosome?
Histone
35
What is a nucleosome?
A unit of DNA wrapped around a histone protein core
36
Define chromatin.
Complex of DNA and histone proteins that condenses to form chromosomes during cell division
37
What is a chromosome?
Thread-like structure composed of condensed chromatin that carries genetic information in the form of genes
38
What are sister chromatids?
Identical copies of a chromosome that are joined together at a centromere after DNA replication
39
What is the centromere?
Location on a DNA chromosome where sister chromatids attach
40
Differentiate between unreplicated and replicated chromosomes.
Unreplicated: single, linear DNA molecule; Replicated: consists of two identical sister chromatids connected at the centromere
41
What are the phases of the cell cycle?
Interphase (G1, S, G2) and Mitosis phase (M)
42
What occurs during the G0 phase of interphase?
Cells continue to function normally but do not prepare for cell division
43
What happens during the G1 phase of interphase?
Cell grows and carries out normal functions in preparation for cell division
44
What is the S phase of interphase known for?
DNA is replicated producing sister chromatids
45
What occurs during the G2 phase of interphase?
Cell prepares for cell division
46
Describe prophase in mitosis.
Sister chromatids condense into visible chromosomes; nuclear envelope breaks down; mitotic spindle starts forming
47
What happens during prometaphase?
Nuclear envelope fully dissolves; spindle attaches to kinetochore of sister chromatids
48
What is the metaphase?
Chromosomes line up single-file at the metaphase plate
49
What occurs during anaphase?
Sister chromatids separate; spindle pulls each chromosome toward opposite poles of the cell
50
What happens during telophase?
Chromosomes decondense; nuclear envelopes reform around each set of chromosomes
51
What is cytokinesis?
Cytoplasm division that generates two identical daughter cells
52
How do animal cells undergo cytokinesis?
Cleavage furrow 'pinches' the cell membranes until the cell splits into two
53
How do plant cells undergo cytokinesis?
Formation of a cell plate
54
What is the outcome of mitosis?
Creates two genetically identical nuclei, maintaining the chromosome number
55
What happens when the checkpoints in the cell cycle fail?
Cancer arises
56
What is a tumor?
Mass of cells resulting from uncontrolled cell division
57
Differentiate between benign and malignant tumors.
Benign: local and non-spreading; Malignant: spreading and invades neighboring tissues
58
What is metastasis?
Cancer cells spread from the original tumor to other parts of the body
59
What are the characteristics of cancer cells compared to normal cells?
They lose specialization, are 'immortal', and can regenerate telomeres
60
What is a proto-oncogene?
Normal gene that regulates cell growth and division
61
What is an oncogene?
Mutated or overexpressed proto-oncogene that promotes uncontrolled cell division
62
What is the role of a tumor-suppressor gene?
Regulates cell division, repairs DNA damage, and prevents uncontrolled growth
63
What is the key difference between proto-oncogenes and tumor-suppressor genes?
Proto-oncogenes promote cell division, while tumor-suppressor genes inhibit cell division
64

Bio 101- Lecture Tes 3 (1 decks)

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