Biology Concepts Review

Allele Frequencies

Change in allele frequencies can be caused by:

• Natural selection
• Mutation
• Gene flow
• Genetic drift

Viral Reproduction

Steps of viral reproduction:

1. Attachment
2. Entry
3. Integration
4. Synthesis of viral components
5. Viral assembly
6. Release

Antibody Variable Regions

Primary function of the variable regions in antibodies: To bind specifically to antigens and determine the antibody's specificity.

Immunity

Innate Immunity

Innate (aka nonspecific) immunity is present at birth and functions the same way regardless of the pathogen. It involves:

• Phagocytosis
• Inflammation

In response to injury and/or pathogens, innate immune cells release paracrine signaling molecules such as cytokines and histamine that trigger inflammation. External pathogen features that can be recognized by innate immune cells are called pathogen-associated molecular patterns (PAMPs). Phagocytes engulf and destroy pathogens by endocytosis.

Acquired Immunity

Acquired (aka specific) immunity develops after exposure to a specific pathogen and targets it specifically. It:

• Develops after exposure to foreign substances
• Is induced by specific foreign molecules (antigens)
• Is mediated by a specific class of leukocytes (white blood cells) called lymphocytes (B cells and T cells)

In humoral immunity, B cells recognize a specific antigen, differentiate, and secrete specialized proteins that target that antigen (antibodies). Helper T cells are involved in activating the B cell response.

In cell-mediated immunity, cytotoxic T cells that recognize specific antigens are activated and then attack antigen-bearing cells directly. Helper T cells are also involved in activating the T cell response.

Ploidy

Ploidy is important: one haploid sperm fuses with one haploid egg to form a diploid zygote.

Embryonic Development

The embryo’s cells use positional information to determine what cell types to differentiate into. They become more differentiated as development proceeds, with most eventually being locked into different cell fates.

Frog Development

Stages of frog development:

1. Fertilization
2. Cleavage
3. Gastrulation
4. Neurulation
5. Organogenesis

Gametogenesis

Spermatocytes divide symmetrically – each diploid primary spermatocyte will go through meiosis I and II to produce four mature sperm.

Oocytes instead divide asymmetrically – only one mature egg will be produced from meiosis I and II of a primary oocyte (polar bodies degenerate).

Fertilization

The acrosome is the tip of a sperm cell that contains the enzymes that carry out the acrosomal reaction, which initiates an intracellular signaling cascade in fertilization.

The cortical reaction is a cell signaling cascade that results in the release of Ca2+, which causes cortical granules to be released. Cortical granules destroy sperm-binding proteins so no more sperm can enter.

Cleavage

Cleavage occurs during the initial stage of rapid cell division in embryonic development.

Gastrulation

The purpose of gastrulation is major cell movement and differentiation into three germ layers.

Neurulation

Neurulation is responsible for the development of the spinal cord and body region. The blastula invaginates into a gastrula, and cells differentiate into three germ layers.

Germ Layers

Germ line cells are specialized for the production of gametes.

Germ layers refer to different somatic cell types found in different parts of the developing embryo (ectoderm, mesoderm, and endoderm).

Vaccines

Vaccines boost the immune system's ability to respond to and fight specific pathogens.

SARS-CoV-2 Vaccines

Technology used in SARS-CoV-2 vaccines: mRNA

Microbiome

: The collection of microorganisms living in a particular environment, like the human body