Bio Module 3- Genes, Genetics, and Cell Division
Lesson 14: Control of Gene Expression
🔬 Molecular and Transcriptional Regulation Terms
Activator: a protein that binds to the promoter to enhance the binding of RNA polymerase (or, a protein that binds to the promoter to stabilize RNA polymerase binding and increases transcription of the associated protein-coding genes).
cAMP (Cyclic AMP): a signaling molecule that is involved in glucose and energy metabolism in E. coli (and whose concentration rises as the concentration of glucose falls).
Coding region: The region of an operon that includes the genes for the biosynthesis enzymes.
Enhancers: DNA sequences that help augment transcription; they are binding sequences, or sites, for specific transcription factors.
Exons: sequence present in final mature mRNA; protein-coding segments.
Gene: The basic unit of heredity; a sequence of DNA that codes for a functional product (e.g., RNA or protein).
General transcription factors (or basal transcription factors): proteins that bind to the core promoter region to assist with the binding of RNA polymerase.
lac operon: a typical inducible operon that includes the genes needed to use lactose as an energy source.
Negative control: a mechanism where a repressor protein actively binds to the operator to keep the genes turned off.
Operator: a region of DNA to which a repressor protein can bind to block the action of RNA polymerase.
Operon: a block of genes that are needed for a specific function, or that are involved in the same biochemical pathway, and are encoded together and transcribed into a single mRNA.
Positive control: a mechanism where proteins bind to the promoter sequences that act as positive regulators to turn genes on and activate them.
Primary transcript: The newly transcribed RNA molecule; also called pre-mRNA in eukaryotes.
Promoter: a DNA sequence immediately upstream of the coding sequence to which RNA polymerase binds to initiate transcription.
Repression: a mechanism in which a repressor protein actively binds to the operator to keep the genes turned off (negative regulation).
Repressor: a protein that binds to an operator region to block the action of RNA polymerase.
RNA polymerase: The enzyme that synthesizes an RNA strand from a DNA template.
Specific transcription factors: proteins that bind to various regions outside of the core promoter region and interact with the proteins at the core promoter to enhance or repress the activity of the polymerase.
Transcriptional gene regulation: The primary method in prokaryotes (and an important one in eukaryotes) to control what type of protein and how much of each protein is expressed by regulating DNA transcription.
Transcription complex: The assembly of general transcription factors, RNA polymerase, and other proteins that initiate transcription.
Transcription factors: proteins that control the initiation of transcription by binding to the promoter and other regulatory elements.
trp operon: an operon containing the genes for the five tryptophan biosynthesis enzymes.
UTR (Untranslated Region): Region just upstream (5' UTR) or downstream (3' UTR) of the protein-coding region in an RNA molecule that is not translated.
🧬 Epigenetic Regulation Terms
Chromatin remodeling complex: A protein machine that slides nucleosomes down the DNA to open a chromosomal region, allowing for the transcriptional machinery to initiate transcription.
Histones: proteins that package and order DNA into structural units called nucleosome complexes.
Histone acetylation: The addition of acetyl groups to histone tails, which relaxes the binding of DNA to the histones and opens chromatin regions for transcription.
Nucleosomes: structural units formed by the winding of DNA strands around histone proteins.
⚙ Post-Transcriptional, Translational, and Post-Translational Terms
Alternate splicing: The mechanism of splicing different ways to produce different proteins from the same gene.
Chemical modification of proteins: The addition or removal of groups (like methyl, phosphate, acetyl, and ubiquitin groups) from proteins to regulate their activity or the length of time they exist in the cell.
Double stranded RNA (dsRNA): RNA that is double-stranded and can be introduced into cells to cause gene silencing (a precursor to siRNA/miRNA).
Export inhibition: The control mechanism where a pre-mRNA is prevented from being transported from the nucleus to the cytoplasm for translation.
Induction: The process where a small molecule inactivates a repressor or activates an activator to increase transcription.
Initiation complex: The complex that assembles to start the process of translation.
mRNA editing: A mechanism that changes the sequence of the primary transcript after it has been transcribed.
miRNA (microRNA): Small regulatory RNA molecules that bind to complementary sequences in mRNA and inhibit translation or target the mRNA for degradation.
Post-transcriptional gene regulation: Regulation that occurs after the RNA is transcribed but before it is translated into protein, including RNA processing and export to the cytoplasm.
Post-translational gene regulation: Regulation that occurs after the protein has been made, including chemical modifications of proteins and protein degradation.
Proteasome: An organelle that functions to remove proteins that have been marked for degradation (by ubiquitin) and breaks them down.
RNA interference (RNAi): A cellular process that developed to protect the cell from viral or parasitic infections where small RNA molecules (miRNA and siRNA) shut off gene expression.
RNA splicing: The process of removing introns and reconnecting exons in the primary transcript to produce a mature mRNA.
siRNA (small interfering RNA): Small regulatory RNA molecules that bind to complementary sequences in mRNA and inhibit translation or target the mRNA for degradation.
Small RNAs: A general term for small regulatory RNA molecules like miRNA and siRNA.
Spliceosomes: complexes of proteins and RNA molecules that carry out RNA splicing.
Ubiquitin: A small protein that, when added to a target protein, marks that protein for degradation (it acts like a flag).
Ubiquitination: The process of adding a ubiquitin group to a protein, which marks that protein for degradation.
Lesson 14: Cell Division: Mitosis
🧬 Cell Division: Mitosis Definitions (OpenStax Biology 2e)
I. Chromosome Structure and Packing
Histones: Proteins that associate with DNA to form nucleosomes.
Nucleosome: The beadlike, histone DNA complex.
Chromatin: DNA-protein complex that forms chromosomes.
Euchromatin: Loosely packed chromatin that is accessible for transcription.
Heterochromatin: Densely packed chromatin that is not typically accessible for transcription.
10 nm fiber: DNA wound around histones to form nucleosomes.
Solenoid: Condensation of the 10-nm fiber into a 30-nm fiber via tighter coiling.
30 nm fiber: The solenoid structure formed by the condensation of the 10-nm fiber.
Centromere: Constricted region of a chromatid where sister chromatids are most tightly attached.
Kinetochore: A protein structure on the centromere that is the attachment point for the mitotic spindle.
Sister chromatids: The two identical copies of a chromosome after DNA replication, attached by cohesin proteins.
Cohesin proteins: Proteins that seal sister chromatids together at their centromeres until anaphase.
II. Ploidy and Homology
Karyotype: An arrangement of chromosomes according to length.
Haploid ($n$): Cell, nucleus, or organism containing one set of chromosomes.
Diploid ($2n$): Cell, nucleus, or organism containing two sets of chromosomes.
Homologous chromosomes: Chromosomes that are the same length and have the same genes in the same location; one comes from each parent.
Homolog: Individual chromosome from a homologous pair.
III. Cell Cycle Phases and Events
Daughter cell: One of the two identical cells produced after a single parent cell has divided.
Interphase: The long preparatory period of the cell cycle during which chromosomes are replicated and the cell grows (G1, S, and G2 phases).
G1 phase: The first growth phase; the cell accumulates building blocks and energy reserves.
S or Synthesis phase: The phase during which nuclear DNA is duplicated (DNA replication).
G2 phase: The second growth phase; the cell replenishes energy and synthesizes proteins necessary for chromosome movement.
M or Mitotic phase: The phase during which duplicated chromosomes and cytoplasm are separated, resulting in two new cells.
Mitosis: The division of genetic material (nuclear division, or karyokinesis).
IV. Stages of Mitosis and Cytokinesis
Centrosome: A structure containing a pair of centrioles that orchestrates chromosome movement during mitosis.
Prophase: The first stage of mitosis; chromatin coils and condenses into visible chromosomes.
Metaphase: The stage where sister chromatids line up along a linear plane in the middle of the cell.
Spindle equator (metaphase plate): The plane through the center of the spindle where the sister chromatids are positioned during metaphase.
Anaphase: The stage when sister chromatids separate and are pulled to opposite ends of the cell.
Telophase: The final stage of mitosis; two new daughter nuclei form at either end of the dividing cell.
Cytokinesis: The physical separation of the cytoplasmic components into the two daughter cells.
Cleavage furrow: A constriction formed by the contractile ring during cytokinesis in animal cells.
Contractile ring: The actin ring that separates daughter cells in animal cells during cytokinesis.
Cell Plate: A structure formed during plant cell cytokinesis that grows into a new cell wall.
V. Cell Cycle Control and Cancer
Checkpoint: Points in the cell cycle where progression can be halted until conditions are favorable.
G1/S checkpoint: Determines whether all conditions are favorable for the cell to irreversibly commit to division.
G2/M checkpoint: Ensures all chromosomes have been replicated and DNA is not damaged before entering mitosis.
Metaphase or Spindle checkpoint: Determines whether all sister chromatids are correctly attached to the spindle microtubules.
Growth factor: A signaling molecule that promotes cell division.
Proto-oncogene: A normal gene that codes for positive cell cycle regulators (proteins that promote progress).
Oncogene: A mutated proto-oncogene that can cause a cell to become cancerous.
Tumor suppressor gene: A gene that codes for negative regulator proteins that prevent the cell from undergoing uncontrolled division.
VI. Prokaryotic Cell Division
Binary fission: Prokaryotic cell division process that results in two identical daughter cells.
Septum: A wall formed across the cell during prokaryotic cell division (binary fission).
Lesson 15: Cell Division: Meiosis
🧬 Cell Division: Meiosis Definitions (OpenStax Biology 2e)
I. Core Meiosis and Sexual Reproduction Terms
Meiosis: A two-step cell division process that results in four cells with half the number of chromosome sets as the original cell.
Sexual reproduction: The union of two cells from two individual organisms.
Gametes: A haploid reproductive cell or sex cell (sperm or egg).
Fertilization: The union of two haploid cells (gametes) from two individual organisms.
Zygote: A diploid cell resulting from the fusion of two haploid gametes.
Meiosis I: The first round of meiotic cell division; sometimes termed reduction division because the resulting cells are haploid.
Meiosis II: The second round of meiotic cell division following meiosis I.
Genetic variation: The diversity of alleles and genotypes in a population.
II. Stages and Structures of Meiosis I
Prophase I: The first stage of meiosis I; homologous chromosomes condense and form complexes with one another.
Synapsis: The formation of a close association between homologous chromosomes during prophase I.
Synaptonemal complex: A protein lattice that forms between homologous chromosomes during prophase I.
Tetrad: Two duplicated homologous chromosomes (four chromatids) bound together by chiasmata during prophase I; also called a bivalent.
Bivalent: Two duplicated homologous chromosomes (four chromatids) bound together by chiasmata during prophase I; also called a tetrad.
Crossing over: The exchange of genetic material between homologous chromosomes, resulting in recombinant chromosomes.
Recombination: The process of prophase I in which homologous chromosomes exchange genetic material.
Chiasmata (singular, chiasma): The structure that forms at the crossover points after genetic material has been exchanged.
Anaphase I: The stage of meiosis I during which homologous chromosomes are separated from each other.
Independent assortment: The random nature by which each pair of homologous chromosomes separates during meiosis I, generating haploid cells with different combinations of parental chromosomes.
III. Meiosis Errors
Nondisjunction: The failure of synapsed homologs to completely separate and migrate to separate poles during the first meiotic division or the failure of sister chromatids to separate during the second meiotic division.
Aneuploid: An individual with an error in chromosome number; includes chromosome segment deletions and duplications.
Lesson 16: Inheritance of Genetic Information Part 1
🧬 Inheritance of Genetic Information Definitions (OpenStax Biology 2e)
I. Core Concepts and Terminology
Genes: Are composed of DNA and are linearly arranged on chromosomes. They specify the sequences of amino acids, which are the building blocks of proteins.
Alleles: Gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes.
Trait: A variation in the physical appearance of a heritable characteristic.
Genotype: An organism’s underlying genetic makeup, consisting of both physically visible and non-expressed alleles.
Phenotype: An organism’s observable traits.
Homozygous: Diploid organisms that have two identical alleles for a gene on their homologous chromosomes.
Heterozygous: An individual having two different alleles for a given gene.
Dominant: A trait that is observable and expressed in the $F_1$ offspring when a heterozygous individual is present.
Recessive: A trait that is non-expressed in the $F_1$ offspring but reappears in the $F_2$ generation; the trait is only expressed when two copies of the allele are present.
Mutations: Changes in the nucleotide sequence of an organism’s DNA.
Genetic disorders: Inherited conditions that can arise when chromosomes behave abnormally during meiosis or are caused by specific gene mutations.
II. Mendelian Experiments and Crosses
True-breeding: Organisms that always produce offspring that look like the parent (i.e., are homozygous for the characteristic being examined).
Not true-breeding: Organisms that are not pure lines (i.e., they are heterozygous and do not always pass the same trait to their offspring).
Hybrid: A term used to refer to an offspring resulting from a cross between two different species. (Note: In the context of Mendel's work, it refers to an offspring from a cross between two true-breeding parents for different traits.)
$F_1$ generation (First Filial): The offspring resulting from the cross of the $P_0$ (parental) generation.
$F_2$ generation (Second Filial): The offspring resulting from the self-cross or mating of individuals from the $F_1$ generation.
Monohybrid cross: A cross between two true-breeding parents that express different traits for only one characteristic.
Dihybrid cross: A cross between two true-breeding parents that express different traits for two characteristics.
Punnett square: A visual tool used to determine the probability of an offspring having a particular genotype (and consequently phenotype) by tabulating the possible combinations of parental gametes.
Mendelian ratio: The predictable genotypic and phenotypic ratios observed in the $F_2$ generation (e.g., $3:1$ phenotypic ratio for a monohybrid cross).
III. Mendel's Principles
Principle of segregation (Law of Segregation): Paired unit factors (alleles) must segregate equally into gametes such that offspring have an equal likelihood of inheriting either factor.
Principle of independent assortment (Law of Independent Assortment): Genes do not influence each other with regard to the sorting of alleles into gametes; every possible combination of alleles for every gene is equally likely to occur. (Note: This applies to genes on different chromosomes or genes far apart on the same chromosome).
IV. Non-Mendelian Inheritance and Analysis
Incomplete dominance: A situation in which the heterozygote exhibits a phenotype that is intermediate between the homozygous phenotypes.
Codominance: A situation in which the simultaneous expression of both of the alleles in the heterozygote is observed.
Multiple alleles: A condition where a gene has more than two alleles existing in a population.
Pleiotropy: The phenomenon where one gene affects multiple characteristics.
Epistasis: An interaction between genes that is antagonistic, such that one gene masks or interferes with the expression of another.
Polygenic inheritance: An inheritance pattern in which multiple genes contribute to a single observable trait.
Environmental influence: Factors outside of the genome (like diet, temperature, or exposure) that can modify the expression of a genotype and alter the phenotype.
Carrier: An individual who is heterozygous for a recessive disorder and may not display the disease's symptoms but can transmit the allele to their offspring.
Pedigree: A chart that maps the inheritance of a trait in a family.
Lesson 17: Inheritance of Genetic Information Part 2
🧬 Inheritance of Genetic Information Part II Definitions (OpenStax Biology 2e)
I. Chromosomes and the Chromosomal Theory
Chromosomal theory of inheritance: The theory that identifies chromosomes as the genetic material responsible for Mendelian inheritance.
Chromosomes: Threadlike nuclear structures consisting of DNA and proteins that serve as the repositories for genetic information.
Genes: Functional units of chromosomes that determine specific characteristics by coding for specific proteins.
Loci (singular, locus): The position of a gene on a chromosome.
Alleles: Gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes.
Autosomes: Any of the non-sex chromosomes.
Sex chromosomes: The single pair of non-homologous chromosomes that determine the sex of an individual.
X-chromosome: One of the two types of sex chromosomes.
Y-chromosome: One of the two types of sex chromosomes; it is much shorter than the X chromosome and contains fewer genes.
SRY gene: The gene on the Y chromosome that triggers the development of male characteristics.
II. Mendelian Terms (Recap)
Dominant: A trait that is observable and expressed in the $F_1$ offspring when a heterozygous individual is present.
Recessive: A trait that is non-expressed in the $F_1$ offspring but reappears in the $F_2$ generation; expressed only when two copies of the allele are present.
Genotype: An organism’s underlying genetic makeup.
Phenotype: An organism’s observable traits.
Homozygous: Having two identical alleles for a gene.
Heterozygous: An individual having two different alleles for a given gene.
Hybrid: The offspring resulting from the cross of two true-breeding parents that differ in one or more traits (in the context of Mendel's work).
$F_1$ generation: The offspring resulting from the cross of the parental generation.
$F_2$ generation: The offspring resulting from the self-cross or mating of individuals from the $F_1$ generation.
Independent assortment (Principle of independent assortment): The rule that genes do not influence each other with regard to the sorting of alleles into gametes.
Testcross: A cross between a dominant-expressing organism (whose genotype is unknown) and an organism that is homozygous recessive for the same characteristic.
Progeny: Offspring (an individual resulting from a cross).
Mutations: Changes in the nucleotide sequence of an organism's DNA.
Epistasis: An interaction between genes in which one gene masks or interferes with the expression of another.
III. Genetic Linkage and Mapping
Linked: Genes that are located close to each other on the same chromosome and tend to be inherited together.
Crossing over (Crossover): The exchange of genetic material between homologous chromosomes, resulting in recombinant chromosomes.
Genetic recombination: The process of crossing over in which homologous chromosomes exchange genetic material.
Recombinant chromosomes: Chromosomes where genetic material has been exchanged through crossing over.
Recombinant gametes: Gametes that have new allele combinations resulting from crossing over.
Recombination frequency: The average number of crossovers between two alleles; it correlates with their genetic distance.
Centimorgan (cM): A relative distance that corresponds to a $0.01$ recombination frequency (also called a map unit).
Genetic map: An illustration that lists genes and their location on a chromosome.
Linkage analysis: A procedure that analyzes the recombination frequency between genes to determine if they are linked.
Two-point cross: A cross involving two genes that is used in linkage analysis.
IV. Sex-linked Inheritance and X-Inactivation
Sex-linked traits (X-linked trait): Traits whose alleles are located on the X chromosome but not on the Y chromosome.
Colorblindness: A recessive X-linked condition in humans.
Hemophilia: A recessive X-linked disorder in which the blood fails to clot properly.
Dosage compensation: The mechanism in female cells that equalizes the amount of product produced by X-linked genes in males and females.
X-inactivation: The process by which one of the two X chromosomes in every female somatic cell is inactivated and compacted into a Barr body.
Barr body: A compacted, nonfunctional X chromosome in the nuclei of female mammalian cells.
Genetic mosaic: A female mammalian cell population in which some cells express the paternal X-linked alleles and some express the maternal X-linked alleles due to random X-inactivation.
V. Chromosomal Disorders (Aneuploidy)
Nondisjunction: The failure of homologous chromosomes or sister chromatids to separate correctly during meiosis.
Aneuploidy: An individual with an error in chromosome number; includes chromosome segment deletions and duplications.
Monosomy: The state of having only one copy of a given chromosome in an otherwise diploid cell ($\mathbf{2n - 1}$).
Trisomy: The state of having three copies of a given chromosome in an otherwise diploid cell ($\mathbf{2n + 1}$).
Genetic disorders: Inherited disorders that can arise from abnormalities in chromosome number or chromosomal structural rearrangements.
Down's syndrome (Trisomy 21): A human disorder characterized by trisomy of chromosome 21.
Turner syndrome (XO): A human disorder characterized by a single X chromosome (monosomy of the sex chromosome).
Triple X syndrome (XXX): A human disorder characterized by three X chromosomes (trisomy of the X chromosome).
Klinefelter syndrome (XXY): A human disorder characterized by an extra X chromosome in males.
Jacob's syndrome (XYY): A human disorder characterized by an extra Y chromosome in males.
Sickle Cell Anemia: A recessive genetic disorder that causes red blood cells to assume a sickle shape.
VI. Other Non-Mendelian Mechanisms
Organelle genomes: The DNA contained within organelles like mitochondria and chloroplasts.
Mitochondria: Oval-shaped, double-membrane organelles that have their own ribosomes and DNA and carry out cellular respiration.
Chloroplast: A plant cell organelle that carries out photosynthesis and has its own DNA.
Maternal inheritance: A non-Mendelian inheritance pattern in which offspring only inherit traits from the maternal parent because only the egg contributes organelles (like mitochondria and chloroplasts) to the zygote.
Genomic imprinting: An epigenetic process where one of the two alleles for a gene is silenced depending on which parent transmitted it.
Epigenetic mechanisms: Modifications to DNA or associated proteins that affect gene expression without altering the DNA sequence itself.
Single nucleotide polymorphisms (SNPs): Variations in a single nucleotide that occur at a specific position in the genome.
Short Tandem Repeats (STRs): Short DNA sequences that are repeated a different number of times in different individuals.
Lesson 18: Biotechnology
🔬 Lesson 18: Biotechnology and Genetics Definitions
I. Genetic Tools and Techniques
Selective Breeding: A process used for breeding livestock and crops (long before people understood the scientific basis of these techniques) to select for plant varieties or animals with desirable traits.
Genetic Diversity (or Genetic Variation): The raw material for evolution and adaptation in a species.
Gene Editing: The modification of the genome, such as the use of CRISPR/Cas9 technology to correct errors in the genome and turn on or off genes in cells and organisms.
CRISPR/Cas9: A gene-editing technology that involves a guide RNA to match a desired target gene and Cas9, an endonuclease that causes a double-stranded DNA break, allowing modifications to the genome.
Restriction Endonuclease (Restriction Enzyme): An enzyme, first identified in bacteria, that cleaves double-stranded DNA at specific recognition sequences.
Ligase (DNA Ligase): An enzyme that catalyzes the formation of phosphodiester linkages to seal the nicks or gaps that remain between newly synthesized DNA fragments.
DNA polymerase (DNA pol): An enzyme that adds nucleotides one-by-one to the growing DNA chain that is complementary to the template strand.
Nuclease: An enzyme that breaks down nucleic acids. For example, DNA polymerase I has exonuclease activity to remove RNA primers.
Plasmid: A smaller loop of DNA found in some prokaryotes that is not essential for normal growth. In biotechnology, it is often manipulated to serve as a vector to carry foreign DNA.
Origin of Replication: A particular sequence in the genome where DNA replication begins. (Often abbreviated ori in plasmids).
Selection marker: A gene, often carrying antibiotic resistance, that is included on a plasmid to allow researchers to identify cells that have successfully taken up the plasmid.
Ligation: The process of sealing the gap between DNA fragments, typically catalyzed by the DNA ligase enzyme to join the insert DNA and the vector DNA.
Sticky ends: Short, single-stranded overhangs generated by the staggered cutting of DNA by certain restriction enzymes. They are "sticky" because they can easily pair with complementary sequences.
II. Polymerase Chain Reaction (PCR) and Gel Electrophoresis
PCR (Polymerase Chain Reaction): A technique that can amplify short DNA or RNA stretches to rapidly make millions of copies.
Denature (in PCR context): The process of separating the two complementary strands of DNA by exposing them to high temperatures.
Annealing (in PCR context): The process of cooling the single DNA strands to allow the primers to bind to the template DNA.
Primers: Short, single-stranded RNA segments synthesized by RNA primase that provide the free $3'-OH$ end required for DNA polymerase to start adding nucleotides. (In PCR, these are typically short DNA strands).
Elongation (in PCR context): The step where the DNA polymerase adds nucleotides one-by-one to the primer, extending the new DNA strand complementary to the template.
GFP protein (Green Fluorescent Protein): A protein that, in a molecular biology context, is often used as a reporter gene; when expressed, it allows researchers to visually track a gene or protein of interest because it makes the organism glow green under UV light.
Gel Electrophoresis: A technique that scientists use to separate molecules (like nucleic acids or proteins) on the basis of size, using an electric field and a semisolid, porous gel matrix.
Anode: The positive electrode in an electrolytic cell (like a gel electrophoresis unit) to which the negatively charged DNA fragments migrate.
Cathode: The negative electrode in an electrolytic cell (like a gel electrophoresis unit) from which the negatively charged DNA fragments are pulled away.
III. Genetic Modification and Development
Transformation: The process in which a cell, often a bacterium, takes up a plasmid or other foreign DNA from its environment.
GMOs (Genetically Modified Organisms): Organisms that have received recombinant DNA from other species (referred to as transgenic in the textbook for plants).
Ti Plasmid (Tumor-inducing plasmid): Plasmids naturally found in Agrobacterium tumefaciens that contain genes to produce tumors in plants; researchers manipulate them to introduce desired DNA fragments into plant hosts.
Agrobacterium tumefaciens: A disease-causing bacterium used by researchers to naturally transfer DNA (from its Ti plasmid) into a plant host.
Gametes: Specialized cells (e.g., egg and sperm) that are haploid (contain one set of chromosomes) and fuse during sexual reproduction.
Zygote: A fertilized egg that contains two sets of chromosomes (diploid), formed when gametes unite.
Somatic cells: All cells of a multicellular organism except the gametes or reproductive cells.
Germlines (Germ cells): The cells that give rise to the gametes (reproductive cells).
Embryo: The stage of a multicellular organism's development that follows fertilization of the egg.