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Genetics, DNA, RNA and Cells Cheat Sheet by

Biology, Genetics and Cells.

Differ­ences Between Mitosis and Mitosis

Number of Cell Divisions
Number of Daughter Cells
Role in Animals
Tissue Growth and Asexual Reprod­uction
Formation of Gametes (For Sexual Reprod­­uc­tion)
Role in Plants
Plant Grows or Produces Gametes
Sporop­hytes Produces Spores


Mitosis is the process of asexual reprod­uction. Mitosis ensures that each daughter cell contains chromo­somes that are exact copies.


Meiosis is the process of sexual reprod­uction. Meiosis ensures that each gamete contains exactly half of the chromo­somes of the parent cell; It also contains two divisions - Meiosis I and Meiosis II.

Human Chromo­somes

Males have 22 Identical chromosome pairs. This consists of 1 X chromosome and 1 Y Chromo­some.
Females have 22 Identical pairs of chromo­somes, Plus a pair of X chromo­somes.
Although X and Y are different, These chromo­somes in Men are able to behave as though they are pairs.
X and Y chromo­somes are how we Identify Sex in Humans.
Healthy Humans have a total of 46 Chromo­somes, This comprises of 22 Pairs (Known as Autoso­mes), Plus two sex chromo­somes, X and Y (Or 2 X chromo­somes for Females.)

Human Chromo­somes

Chromosome Abnorm­alities

Down Syndrome
Babies with Down syndrome have an extra copy of chromosome 21. A medical term for having an extra copy of a chromosome is 'trisomy.'
Turner Syndrome
Turner syndrome is a female­-only genetic disorder.A girl with Turner syndrome only has 1 normal X sex chromo­some, rather than the usual 2.
Klinef­elter Syndrome
Klinef­elter syndrome (sometimes called Klinef­elt­er's, KS or XXY) is where boys and men are born with an extra X chromo­some.
Triple-X Syndrome
Trisomy X, also called triple X syndrome or 47,XXX, is charac­terized by the presence of an additional X chromosome in each of a female's cells.
Edwards Syndrome
Edwards Syndrome (Trisomy 18) is a genetic disorder caused by the presence of a third copy of all or part of chromosome 18. Many parts of the body are affected. Babies are often born small and have heart defects.
Patau syndrome
Trisomy 13 (also called Patau syndrome) is a genetic disorder in which a person has 3 copies of genetic material from chromosome 13, instead of the usual 2 copies. Causes a list of health problems.
The most common type of chromo­somal abnorm­ality is known as aneupl­oidy, an abnormal chromosome number due to an extra or missing chromo­some.


A genotype is an organisms genetic inform­ation also known as the genetic makeup of a cell, an organism, or an individual usually with reference to a specific charac­­te­r­i­stic. Genotypes are the inform­ation stored in a complete set of genes.


A Phenotype refers to inherited traits that can be physically observed. Phenotypes is the end product, it is the result of the genetic inform­ation.

Cell Structure

Cell Membrane
The cell membrane supports and protects the cell. It controls the movement of substances in and out of the cells. It separates the cell from the external enviro­nment. The cell membrane is present in all the cells.
The cell membrane is the outer covering of a cell within which all other organe­lles, such as the cytoplasm and nucleus, are enclosed. It is also referred to as the plasma membrane.
Cell Wall
The cell wall is the most prominent part of the plant’s cell structure. It is made up of cellulose, hemice­llulose and pectin.
The cell wall is present exclus­ively in plant cells. It protects the plasma membrane and other cellular compon­ents. The cell wall is also the outermost layer of plant cells.
It is a rigid and stiff structure surrou­nding the cell membrane.
The cytoplasm is a thick, clear, jelly-like substance present inside the cell membrane.
Most of the chemical reactions within a cell take place in this cytoplasm.
The cell organelles such as endopl­asmic reticulum, vacuoles, mitoch­ondria, ribosomes, are suspended in this cytoplasm.
The nucleus contains the hereditary material of the cell, the DNA.
It sends signals to the cells to grow, mature, divide and die.
The nucleus is surrounded by the nuclear envelope that separates the DNA from the rest of the cell.

Cell Organelles

The nucleolus is the site of ribosome synthesis. Also, it is involved in contro­lling cellular activities and cellular reprod­uction.
Nuclear membrane
The nuclear membrane protects the nucleus by forming a boundary between the nucleus and other cell organe­lles.
Chromo­somes play a crucial role in determ­ining the sex of an indivi­dual. Each human cells contain 23 pairs of chromo­somes.
Endopl­asmic reticulum
The endopl­asmic reticulum is involved in the transp­ort­ation of substances throughout the cell. It plays a primary role in the metabolism of carboh­ydr­ates, synthesis of lipids, steroids and proteins.
Golgi Bodies
Golgi bodies are called the cell’s post office as it is involved in the transp­ort­ation of materials within the cell
Ribosomes are the protein synthe­sisers of the cell.
The mitoch­ondrion is called “the powerhouse of the cell.” It is called so because it produces ATP – the cell’s energy currency.
Lysosomes protect the cell by engulfing the foreign bodies entering the cell and help in cell renewal. Therefore, they are known as the cell’s suicide bags.
Chloro­plasts are the primary organelles for photos­ynt­hesis. It contains the pigment called chloro­phyll.
Vacuoles store food, water, and other waste materials in the cell.

Phases of Mitosis

Prophase I
Metaphase I
Anaphase I
Telophase I
Prophase II
Metaphase II
Anaphase II
Telophase II

Phases of Meiosis

Prophase I
Metaphase I
Anaphase I
Telophase I + Cytoki­nesis
Meiosis is divided into 6 stages.

Prokaryote and Eukaryote

Eukaryotes are organisms whose cells contain a nucleus and other membra­ne-­bound organe­lles. There is a wide range of eukaryotic organisms, including all animals, plants, fungi, and protists, as well as most algae. Eukaryotes may be either single­-celled or multic­ell­ular.
Prokar­yotes are organisms whose cells lack a nucleus and other organe­lles. Prokar­yotes are divided into two distinct groups: the bacteria and the archaea
Only Eukaryotes have Mitoch­ondria
A single celled organism, in which DNA is not contained within a nucleus.
Only autotr­ophic eukaryotes (Plants and Algae) contain Chloro­plasts
The hereditary material can either be DNA or RNA.
The size of the cells ranges between 10–100 µm in diameter.
The cell size ranges from 0.1 to 0.5 µm in diameter.
Eukaryotic cells are charac­terised by a true nucleus.
Prokar­yotic cells have no nucleus. ome prokar­yotes such as bacteria have a region within the cell where the genetic material is freely suspended. This region is called the nucleoid.
This broad category involves plants, fungi, protoz­oans, and animals.
Prokar­yotes generally reproduce by binary fission, a form of asexual reprod­uction.
They reproduce sexually as well as asexually.

Shapes of Bacterial Cells

Binary Fusion

Stages of Binary Fusion
1. Parent Cell
2. DNA Duplicates
3. Cytoplasm divides
4. Two Daughter Cells
When a bacterial cells starts to grow, once it reaches a certain size the cell splits in half to form two identical, smaller ones (Daughter Cells). As long as conditions are mainta­ined, it will continue to grow and split. One cell becomes Two, Two cells become Four, Four cells become Eight and so on, at a constant rate.

Steps involved in Transc­ription

mRNA (Messenger RNA)
RNA molecule carries the code for a protein
Protein synthe­sisers within a cell
RNA Polymerase
Enzyme that synthe­sises RNA and copies a DNA sequence into a RNA sequence
tRNA (Transfer RNA)
RNA molecules that helps translate an mRNA sequence into a protein
The process by which a cell makes an RNA copy of a piece of DNA. This RNA copy, called messenger RNA (mRNA), carries the genetic inform­ation needed to make proteins in a cell. It carries the inform­ation from the DNA in the nucleus of the cell to the cytoplasm, where proteins are made.


1. RNA Polymerase attaches to the start of a gene
2. RNA Polymerase moves along the DNA, Making strands of mRNA out of free bases in the nucleus
3. The DNA code determines the order that the free bases are added to mRNA
4. mRNA moves out of the nucleus into the cytoplasm


1. Protein factories called ribosomes bind to mRNA
2. A ribosome reads the code in the mRNA three bases at a time
3. tRNA molecules carry amino acids to the ribosomes
4. As each triplet is read, tRNA delivers the corres­ponding amino acid and a chain of amino acids is built
5. The last amino acid is added and the chain folds into a 3D shape to form a protein.

Charac­ter­istics of Cells

1. Cells provide structure and support to the body of an organism.
2. The cell interior is organised into different individual organelles surrounded by a separate membrane.
3. The nucleus (major organelle) holds genetic inform­ation necessary for reprod­uction and cell growth.
4. Mitoch­ondria, a double membra­ne-­bound organelle is mainly respon­sible for the energy transa­ctions vital for the survival of the cell.
5. Lysosomes digest unwanted materials in the cell
6. Endopl­asmic reticulum plays a signif­icant role in the internal organi­sation of the cell by synthe­sising selective molecules and proces­sing, directing and sorting them to their approp­riate locations.

DNA Helicase

DNA Helicase blinds two double stranded DNA and moves along it. As DNA Helicase moves, it seperates the DNA into two strands. The point at which the double stranded DNA is separated into two singe stands is known as a Replic­ation Fork.
DNA Helicase leaves the bases of the parent stands unpaired and exposed.


A word used to describe an organism that carries two copies of its genome, with a copy received from each parents.
Haploid cells produced by meiosis for the specific purpose of sexual reprod­uction. In humans these are egg cells in females and sperm in males.
A word used to describe an organism or cell that carries a single copy of its genome.
Proteins that act as biological catalysts, greatly increasing the rates of chemical reactions.
Red blood cells; small, circular cells with no nuclei that are respon­sible for transp­orting oxygen from the lungs to the rest of the body.
Lag phase
Phase of bacterial growth in which the population of cells adapts to the enviro­nment. This may require the cells to make metabolic changes before optimal growth rates can be achieved
Log phase
Phase of bacterial growth in which the population is able to grow at an optimum rate (logar­ith­mic­ally)
One of the 20 amino acids used to make proteins in most organisms
Literally a large molecule. Used in biology to describe the four major categories of large molecules found in living things, namely nucleic acids, proteins, fats and carboh­ydr­ates.
Describes a smaller molecule that, when polyme­rised into a chain with other monomers, forms a larger polymeric molecule.
A trait displayed by an organism that is passed between genera­tions by genetic inheri­tance.

The Cell Cycle

M Phase (Mitosis and Cytoki­nesis)
GI Phase (Gap I)
G2 Phase (Gap 2)
S Phase (Synth­esis)
A continuous process, divided into 4 phases.
The cell cycle can take anything from a few hours to many weeks to complete. The rate depends on many factors: Type of organism, type of cell (and its size) and the enviro­nment in which the cells are growing.

Animal Cell

Animal cells are Eukaryotic cells surrounded by a cell membrane (Plasma membrane). All animal cells have a large organelle called the nucleus, which is surrounded by a double membrane called the nuclear envelope. The nucleus contains the hereditary material DNA, which is a packaged into chromo­somes. The Cytoplasm is the gel-like substance within the cell membrane in which all intrac­ellular organelles sit.

Plant Cell

Plant cells are eukaryotic cells. Plant cells are surrounded by a cell wall, this is a barrier outside the cell membrane. Plant cells have a large central vacuole, a water filled space enclosed by a membrane. The cytoplasm includes organelles called plastids. These are molecules which are synthe­sised or stored. Chloro­plasts are plastids that contain chloro­phyll (a green pigment used in photos­ynt­hesis). Chloro­plasts are found only in plant cells.

Differ­ences between DNA and RNA

Contains two stands of nucleo­tides joined together by hydrogen bonds to create a Double­-St­randed Helix
RNA is a single stranded molecule
DNA has 4 bases: Adenine, Guanine, Cytosine and Thymine.
Instead of Thymine, it contains Uracil instead.
Sugar Component in DNA is Deoxyr­ibose
Sugar Component in RNA is Ribose
DNA is Missing an Oxygen Atom, it only has 2 Oxygen Atoms
Has 3 Oxygen Atoms
Base Pairing in DNA is A-T and C-G
Base Pairing in RNA is A-U and C-G
'Deoxy' is a term that means an oxygen atom is missing.
Tymine contains an extra carbon atom that is also bonded to 3 hydrogen atoms - A CH3 group.

Compli­mentary Sequences




The four major classes of Biomol­ecules
Carboh­ydrates are chemically defined as polyhy­droxy aldehydes or ketones or compounds which produce them on hydrol­ysis. They are struct­urally very important for many living organisms as they form a major structural component, e.g. cellulose is an important structural fibre for plants.
Proteins are polymers of amino acids arranged in the form of polype­ptide chains. Proteins play both structural and dynamic roles. Myosin is the protein that allows movement by contra­ction of muscles. Most enzymes are protei­naceous in nature.
Nucleic acids
Nucleic acids refer to the genetic material found in the cell that carries all the hereditary inform­ation from parents to progeny. There are two types of nucleic acids namely, deoxyr­ibo­nucleic acid (DNA) and ribonu­cleic acid (RNA). The main function of nucleic acid is the transfer of genetic inform­ation and synthesis of proteins by processes known as transl­ation and transc­rip­tion. The monomeric unit of nucleic acids is known as nucleotide and is composed of a nitrog­enous base, pentose sugar, and phosphate. The nucleo­tides are linked by a 3’ and 5’ phosph­odi­ester bond. The nitrogen base attached to the pentose sugar makes the nucleotide distinct.
Lipids are organic substances that are insoluble in water, soluble in organic solvents, are related to fatty acids and are utilized by the living cell. Lipids are not polymeric molecules. Lipids play a great role in the cellular structure and are the chief source of energy.
Biomol­ecules are the most essential organic molecules, which are involved in the mainte­nance and metabolic processes of living organisms.


A molecule consisting of a nitrog­en-­con­taining base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), a phosphate group, and a sugar (deoxy­ribose in DNA; ribose in RNA).

DNA Ligase

DNA Polymerase

DNA Polymerase converts nucleotide monomers into DNA Polymers. It is the enzyme respon­sible for synthe­sising new DNA.DNA Polymerase moves along the parental strand, using unpaired bases of the parent strand as a template to synthesis a new strand of DNA by base pairing. I.E Where there is an unpaired Thymine in the parent stand, DNA Polymerase adds a comple­mentary Adenine to the new stand.
DNA Polymerase can only move in one direction following the parent stand from its 3' end to its 5' end.


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