IB Biology: Protein Synthesis, Mutations, Evolution, and Homeostasis

Flashcards covering molecular biology, genetics, evolution, biodiversity, and human physiology based on lecture notes.

mRNA

Messenger RNA that is complementary to the template DNA strand and conveys genetic information to ribosomes.

rRNA

Ribosomal RNA found in ribosomes that decodes mRNA into amino acids.

tRNA

Transfer RNA that carries specific amino acids to ribosomes to form polypeptides.

Transcription

The production of mRNA using DNA as a template, occurring in the cytoplasm of prokaryotes and the nucleus of eukaryotes.

Antisense strand

Also known as the template strand, it is the DNA strand used by RNA polymerase to build a complementary mRNA molecule.

Sense strand

Also known as the coding strand, it contains the same sequence as the mRNA (with thymine instead of uracil).

Splicing

The process in eukaryotes where introns are removed and exons are joined to create mature mRNA.

Start codon

The codon $AUG$ (coding for methionine) that initiates translation.

Polysome

A structure consisting of many ribosomes attached to a single mRNA strand simultaneously.

Pleiotropy

The phenomenon where one single gene has multiple effects on an organism's phenotype.

Proteome

The total of all proteins made and used within the body.

Point mutation

The deletion, addition, or replacement of a single nucleotide in the DNA sequence.

Sickle cell anemia

A condition caused by a substitution mutation where adenine is replaced by thymine, changing glutamic acid to valine in hemoglobin.

Alternative splicing

The process of omitting certain exons to result in different versions of proteins with different functions from the same gene.

CRISPR-Cas9

A gene-editing biotechnology originating from the bacterial immune system that uses $Cas9$ to cut DNA at target sites.

Gene knockout

The intentional removal or change of a specific gene so that its expression is permanently deactivated.

Conserved sequences

Gene sequences that remain identical or highly similar across different species over long evolutionary periods.

Regulatory genes

Genes that code for proteins involved in the process of DNA replication.

Structural genes

Genes that code for proteins not involved in DNA replication.

Transcription factors

A group of proteins that influence gene expression by encouraging or blocking the binding of RNA polymerase.

Lac operon

A group of genes in prokaryotes involved in lactose metabolism that are regulated by the same mechanism.

Nucleosome

A structure consisting of negatively charged DNA wrapped around positively charged histone proteins.

Histone acetylation

The addition of acetyl groups to histones, which decreases their positive charge and increases gene expression by making DNA more accessible.

DNA methylation

The addition of methyl groups to cytosine in promoter DNA, which typically leads to decreased gene expression or gene silencing.

Epigenesis

Environmental factors, such as diet or pollution, that affect gene expression without changing the DNA sequence itself.

Mitosis

The division of the nucleus resulting in two genetically identical daughter cells.

Meiosis

Two nuclear divisions that result in four distinct daughter cells with half as many chromosomes as the parent cell.

Chiasma

The point where homologous non-sister chromatids exchange genetic material during crossing over.

Nondisjunction

The failure of chromosomes to separate correctly during division, resulting in aneuploidy (gametes with extra or missing chromosomes).

Cyclin

A protein that regulates the progression of the cell cycle to prevent the overuse of resources.

Oncogene

A mutated proto-oncogene that has the potential to cause cancer through uncontrolled cell growth.

Mitotic index

A calculation determined by the formula: ext{M.I.} = rac{ ext{number of cells in mitosis}}{ ext{total number of cells}}.

Polygenic inheritance

A pattern of inheritance where multiple genes contribute to a single phenotype, creating a continuous distribution such as height or skin color.

Phenotypic plasticity

The capacity of an organism to develop different traits based on its environment by varying gene expression.

Law of Independent Assortment

Mendel's law stating that genes for different traits are sorted into gametes independently of one another.

Evolution

The change in the heritable characteristics of a population over time.

Homologous structures

Anatomical structures that share the same evolutionary origin but may have different functions, such as the pentadactyl limb.

Analogous structures

Structures with different evolutionary origins that perform similar functions, resulting from convergent evolution.

Adaptive radiation

The rapid speciation of a lineage to fill vacant ecological niches.

Allopatric speciation

Speciation that occurs when biological populations are geographically isolated by a physical barrier.

Sympatric speciation

The divergence of species within the same geographical area, often due to temporal or behavioral isolation.

Polyploidy

A condition where an organism has more than two sets of homologous chromosomes, which can lead to abrupt speciation.

Genetic drift

A change in allele frequencies within a population that occurs due to chance rather than natural selection.

Hardy-Weinberg Equation

A mathematical model ($p^2 + 2pq + q^2 = 1$) used to calculate genotype frequencies in a population.

Simpson's Reciprocal Index

A measure used to quantify biodiversity using the formula: D = rac{N(N-1)}{\sum n(n-1)}.

Emergent properties

Properties that arise from the collaborative functioning of a system's parts and do not exist in the individual components alone.

Homeostasis

The maintenance of equilibrium in the internal environment within specific tolerance limits.

Insulin

A hormone released by pancreatic beta ($\beta$) cells that stimulates glucose uptake and glycogen synthesis to lower blood sugar.

Glucagon

A hormone released by pancreatic alpha (arc) cells that stimulates the breakdown of glycogen into glucose to increase blood sugar.

Thyroxin

A hormone produced by the thyroid gland that increases the basal metabolic rate to generate body heat.

Melatonin

A hormone produced by the pineal gland in darkness that controls circadian rhythms and promotes sleep in diurnals.

Superchiasmatic nucleus (SCN)

A structure in the hypothalamus that synchronizes the body's internal clock with the day/night cycle based on light signals from the retina.

Baroreceptors

Stretch-sensitive receptors located in the carotid sinuses and aortic arch that respond to changes in blood pressure.

Chemoreceptors

Receptors that respond to changes in the chemical composition of the blood, such as levels of $CO_2$ or $O_2$.