Notes, summaries, assignments, exams, and problems for Biology

The Cell Cycle

The cell cycle is a repetitive sequence of events that occurs from the time of a cell's formation until its division is completed.

Interphase

The control of cell division resides in the subphases of interphase. During this stage, the cell assembles the carbohydrates, lipids, and proteins needed for internal use and export. Subsequently, the DNA is copied, and protein synthesis drives the cell toward mitosis. Most of a cell's existence is spent in interphase.

Mitosis and Chromosome Number

All somatic cells of a particular species possess the same number of chromosomes.

Mitosis

• Prophase: Chromosomes become visible as rod-like units. Microtubules move one pair of centrioles to opposite poles of the cell, and the nuclear envelope begins

Core Principles of Photosynthesis

The Light-Dependent Reactions

1. When oxygen is released during photosynthesis, what is it a direct by-product of?

   It is a direct by-product of splitting water molecules.

2. What is the role of pigment molecules in a light-harvesting complex?

   Within the thylakoid membranes, they absorb and transfer light energy to the reaction-center chlorophyll.

3. What is directly associated with photosystem I?

   It is directly associated with receiving electrons from the thylakoid membrane's electron transport chain.

4. How can one detect the lack of photosystem II in certain photosynthetic organisms?

   The most effective method is to test for the liberation of O2 in the presence of light, as photosystem II is responsible for splitting water to

Infectious Diseases: Causes, Symptoms & Prevention

Common Infectious Conditions

• CP (Common cold): virus - headache, loss of appetite. Keep hydrated.
• Influenza: virus - high fever, pains in back and muscles. Rest.
• Measles: virus - vomiting, diarrhea, sweating. MMR vaccine.
• Tuberculosis: bacteria - weight loss, fever. Antibiotics.
• Bubonic plague: Yersinia pestis (bacterium) - muscle cramps, chills.
• Cholera: bacterial infection - leg cramps, vomiting, diarrhea. Antibiotics.
• Tetanus: bacteria - stiffness. Vaccination or antitoxin.
• Malaria: protozoa - fever, muscle pain, diarrhoea. Medicines.
• Sleeping sickness: protozoa - fever, itchiness. Different medications.
• Athlete's foot: fungus - infection of the skin. Pharmacy creams.
• Ringworm: fungus - a red rash

Fundamental Knowledge Challenge

Earth Science & Geology

Formation of Smooth Stones

Which of these is the best explanation of how a smooth, round stone becomes smooth? It was in a stream for a long time.

Key Processes of the Water Cycle

Processes of the water cycle include: Evaporation, condensation, sublimation, and so on.

Formation of Water Droplets

The process by which water droplets form is: Condensation.

Astronomy & Physics

Defining Astronomical Bodies

Any astronomical body that revolves around a larger body is called a: Satellite.

Understanding Friction

Friction is the force that: Opposes motion between two surfaces.

Measuring Liquid Resistance to Flow

When scientists measure a liquid's resistance to flow, they are measuring its: Viscosity.

Biology

Transcription: From DNA to RNA

Steps of Transcription

Initiation

• Transcription begins when transcription factors bind to a specific nucleotide sequence of DNA known as the promoter region or the "TATAA box."
• These transcription factors signal RNA polymerase II to attach to the DNA at the promoter.

Elongation

• Once attached to the DNA, RNA polymerase synthesizes a single-stranded RNA molecule in a 5’ → 3’ direction.
• RNA nucleotides are added to the growing polymer, which are complementary to the DNA template.

Termination

• Eventually, RNA polymerase will reach a termination sequence in the DNA.
• This causes RNA polymerase to release the newly synthesized mRNA and to dislodge from the DNA.

Note: The template strand is also known as the antisense strand,

Cellular Processes and Plant Adaptations

41. CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they fix CO2 into organic acids during the night.

Basics of Reproduction and Chromosomes

42. Asexual reproduction requires 1 individual.

43. Eukaryotic chromosomes differ from prokaryotic chromosomes in that they are housed in a membrane-enclosed nucleus.

44. Prior to mitosis, each chromosome of a eukaryotic cell consists of a pair of identical structures called sister chromatids.

The Cell Cycle and Mitosis

45. The genetic material is duplicated during the S phase.

46. Which of the following occurs during interphase? Cell growth and duplication of the chromosomes.

Cancer and Cell Regulation

1. The out-of-control... Continue reading "Essential Biology Concepts: Cell Division and Genetics" »

Meiosis and Genetic Variation

Question 58

Which of the following occurs in meiosis but not in mitosis?

B) synapsis of chromosomes

Question 59

Crossing over normally takes place during which of the following processes?

B) meiosis I

Question 60

Homologous pairs of chromosomes align opposite of each other at the equator of a cell during _____.

B) meiosis metaphase I

Question 61

When homologous chromosomes cross over, what occurs?

C) Corresponding segments of non-sister chromatids are exchanged.

DNA Structure and Replication

Question 62

Which of the following people conducted the experiments that demonstrated that DNA is the genetic material of bacteriophages?

B) Avery, Hershey and Chase

Question 63

One type of virus that infects bacteria is called a

A) phage.

Question

Key Biological Definitions

• Haploid: Having a chromosome complement consisting of just one copy of each chromosome.
• Diploid: Having a chromosome complement consisting of two copies (homologs) of each chromosome.
• Ploidy: The number of sets of chromosomes in a cell or an organism.

Defining Features of Life

Living organisms are characterized by the following traits:

• Reproduction
• Cellular organization
• Metabolism
• Homeostasis
• Heredity
• Growth and development
• Evolution (adaptation)
• Response to stimuli

Comparing Meiosis and Mitosis

Differences

• Prophase I: In meiosis I, sister chromatids form chiasmata and undergo crossing over.
• Outcomes: Meiosis II results in four haploid cells, whereas mitosis results in two diploid cells.
• Genetic Identity: Meiosis I and II result in

Types of Mutations

Point Mutations

A change in a single nucleotide.

• Substitution: One nucleotide is incorrectly added in place of the correct complementary nucleotide.
• Insertion: One or more extra nucleotides are added to the growing DNA strand; this can lead to a frameshift.
• Deletion: One or more nucleotides are eliminated from the growing DNA strand; this can lead to a frameshift.

Chromosome Mutations

Changes in the structure or number of chromosomes.

Structural Mutations

These are due to two simultaneous breakages in nuclear chromosomes. This can cause:

• Deletion: The loss of a chromosomal segment.
• Duplication: A region of the chromosome is repeated.
• Inversion: The change in direction of the chromosomal segment.
• Translocation: A segment splits off from