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

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

Research on Alcohol and Fertility

Research supported by the National Institute of Child Health suggests that alcohol consumption may affect women's fertility.

• Infertility Risks: According to the passage, women who are infertile may consume more than seven cans of beer per week.
• Heavy Drinking: The passage indicates that women who drink heavily face an increased risk of infertility.

Cellular Structure and Function

Plasma Membrane and Organelles

• Selectively Permeable Membrane: Its function is to control what enters and leaves the cell.
• Phospholipid Bilayer: Contains polar and nonpolar ends, forming the plasma membrane.
• Endoplasmic Reticulum: Its structure facilitates the breakdown of chemical bonds.
• Golgi Apparatus: Producing proteins is not a function

Bacterial Identification Using Culture Media

1. Define:

   1. Selective Medium

      A selective medium favors the growth of specific microorganisms while inhibiting others. Examples include:

      • MAC agar (MacConkey agar)
      • Mannitol salt agar
      • Eosin methylene blue agar (EMB)

2. 2. Differential Medium

      A differential medium distinguishes between microorganisms based on their biochemical reactions. Examples include:

      • MAC agar
      • Blood agar
      • Mannitol salt agar
      • Eosin methylene blue agar

MacConkey (MAC) Agar

• MacConkey agar selects for which group of bacteria? Explain.
  • Gram-negative bacteria.
• MacConkey agar media differentiates between enteric bacteria based on what biochemical reaction? Explain.
  • Lactose fermentation (presence or absence of lactase enzyme).
• If the organism is E. coli, what would you

Systemic: Series of Arteries and Veins

A systemic circulation consists of a series of arteries that deliver oxygenated blood to capillary beds within body tissues, and a set of veins that return deoxygenated blood back to the heart.

Coronary: Supplying the Heart

The coronary circulation is similar to the systemic circulation, but its arteries, capillary beds, and veins supply and drain only the heart.

Pulmonary: Blood Flow to the Lungs

The pulmonary circulation features a set of arteries that deliver deoxygenated blood to the capillary beds of the lungs, and a set of veins that return oxygenated blood to the heart.

Blood Flow into the Heart

Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood... Continue reading "Understanding the Circulatory System: Arteries, Veins, and Blood Flow" »

Biology and Genetics Practice Questions

78. Sequence of Events in Translation

Which of the following options most accurately lists the sequence of events in translation?

C) codon recognition → peptide bond formation → translocation → termination

79. Definition of Mutation

Any change in the nucleotide sequence of DNA is called

A) a mutation.

80. HIV Virus Type

What kind of virus is HIV?

C) a retrovirus

81. HIV Enzyme for DNA Synthesis

Which of the following enzymes does HIV use to synthesize DNA on an RNA template?

D) reverse transcriptase

82. Griffith's Experiment and DNA Transfer

In the 1920s, Frederick Griffith conducted an experiment in which he mixed the dead cells of a bacterial strain that can cause pneumonia with live cells of a bacterial strain... Continue reading "Biology Genetics Practice Questions" »

Trigeminal Nerve

The trigeminal nerve controls masticatory muscles. Its sensory fibers receive sensitivity from the face, orbit, nasal cavity, and oral cavity. The trigeminal ganglion (semilunar ganglion/gasserian ganglion) is located anterosuperior to the petrous portion of the temporal bone.

V1 (Ophthalmic Nerve)

V1 is sensory and supplies the front region of the nose, upper eyelid, mucous membranes of the frontal, sphenoid, and ethmoid sinuses, the upper part of the nasal cavity, and the eyeball. V1 has three terminal branches: nasal, frontal, and lacrimal.

Nasal Nerve

• Collateral branches: long ciliary nerve (supplies the eyeball), posterior ethmoidal nerve (supplies the sphenoid sinus, ethmoid cells, and upper portion of the nasal cavity).
• Terminal

Reptile Skin

Dry, thick skin covered with scales prevents moisture loss and protects against predators. Due to their specialized skin, reptiles are entirely dependent on lungs for gas exchange.

Reptile Skeleton

Legs are located under the body, not out to the side like in amphibians. This allows for better support and easier movement on land, increasing their chances of catching prey and avoiding predators. Claws on their feet allow for grasping.

Reptile Heart

Most reptiles have a three-chambered heart, but some (notably crocodilians) have a four-chambered heart. This separates oxygenated blood from deoxygenated blood, enabling more O2 to reach body tissues. This supports the higher level of energy use required by land animals.

Reptile Reproduction

Reptiles... Continue reading "Reptile Biology: Adaptations, Anatomy, and Classification" »

The Human Excretory System

The excretory system comprises the urinary system and various other organs that facilitate the removal of waste products from the body.

Key Excretory Organs and Systems

• Respiratory system: Removes CO2 from the blood and expels it from the body.
• Sweat glands: Located in the skin; produce sweat that evaporates to cool the body.
• Liver: Eliminates waste products resulting from the breakdown of hemoglobin in old red blood cells.
• Urinary system: The primary component of the excretory system, responsible for eliminating waste as urine.

Components of the Urinary System

• Kidneys: A pair of organs that filter waste substances from the blood to produce urine.
• Ureters: Two tubes that transport urine away from the kidneys.
• Bladder: The organ