Genetics and DNA: Mendel's Principles, Inheritance, and Genome Mapping

Gregor Mendel

An Australian monk who used garden sweet pea.

Garden pea

These plants were easily manipulated and can self-fertilize.

Gene

The basic physical and functional unit of heredity, made up of a sequence of DNA.

Homologous chromosomes

When an organism has identical (same) alleles for a gene, either two capital or two lower case.

Allele

One version of a gene. Example: allele for purple flower P or allele for white flower p.

Dominant

An allele that is expressed when present. One copy is enough to show the trait. Example: P.

Recessive

An allele that is expressed only when two copies are present. Example: p.

Homozygous

Both alleles are the same. Examples: PP or pp.

Heterozygous

Alleles are different. Example: Pp.

Genotype

The genetic makeup — the two alleles an organism has for a gene. Example: Pp.

Phenotype

The physical trait you see. Example: purple flower.

True breeding

An organism that always produces offspring with the same trait when selfed or crossed with the same type. Example: true-breeding purple PP always gives purple offspring when crossed with PP.

Locus

Location on a chromosome where a gene resides.

P generation

True-breeding parents.

F1 generation

The F1 generation (first filial generation) is produced by crossing two individuals from the P generation.

F2 generation

The F2 generation (second filial generation) is produced by crossing two F1 individuals with each other.

Mendel's 4 hypotheses

1. Genes have alternate forms called alleles. 2. Each organism inherits two alleles, one from each parent. 3. If the alleles differ, the dominant one determines appearance, and the recessive one is hidden. 4. Gametes carry only one allele because the pair separates during their formation.

Codominance

Both traits show up together.

Incomplete dominance

Blended traits.

Example of codominance

Human blood type AB shows both A and B antigens.

Example of incomplete dominance

Snapdragon flowers: red × white → pink.

Pleiotropy

One gene, multiple phenotypes. Pleiotropy is the impact of a single gene on more than one characteristic. Sickle-cell disease is an example.

Polygenetic inheritance

One trait controlled by two or more genes. Example: Human skin color - determined by several genes controlling pigment amount.

Multifactorial disorder

Diseases have a genetic component and a significant environmental component. Example: heart disease, cancer, mental illness, asthma.

Circle on a pedigree

Female.

Square on a pedigree

Male.

Colored circle on a pedigree

Female with the trait.

Colored square on a pedigree

Male with the trait.

Half-colored square or circle on a pedigree

Carrier.

Sex-linked gene

X-link disorders.

Red-green colorblindness

X-link disorder; It is characterized by a malfunction of light-sensitive cells in the eyes.

Hemophilia

Blood doesn't clot properly.

Freckles

dominant over non-freckles

Widow's peak

dominant over straight hairline

Detached earlobe

dominant over attached earlobe

James Watson and Francis Crick

won the Nobel Prize for the structure of DNA

Rosalind Franklin

a scientist whose X-ray crystallography images of DNA helped reveal the double-helix structure of DNA

James Watson & Francis Collins

led the public Human Genome Project, mapping the human genome using federally funded resources

Craig Venter

led Celera Genomics, a private effort to map the human genome faster using a different sequencing method

Hierarchical shotgun sequencing

the method used by James Watson and Francis Collins to map the human genome

Whole-genome shotgun sequencing

the method used by Craig Venter to map the human genome

National Institutes of Health (NIH) and the Department of Energy (DOE)

the federal government agencies where James Watson and Francis Collins worked when mapping the human genome

Celera Genomics

the name of Craig Venter's biotechnology company

Human genome co-published

to combine public and private efforts, avoid patent conflicts, and share knowledge with the scientific community quickly

Nature and Science

the two scientific journals that co-published the human genome

Differences between RNA and DNA

RNA is single helix, DNA is double helix

Nucleotide bases for DNA

Adenine (A), Thymine (T), Cytosine (C), Guanine (G)

Nucleotide bases for RNA

Adenine (A), Uracil (U), Cytosine (C), Guanine (G)

Base pairing in DNA

A pairs with T, C pairs with G

Base pairing in RNA

A pairs with U, C pairs with G

Origin of replication

DNA unzips, making it RNA, creating a bubble, then the complementary strand comes in, ending with the parental strand and the daughter strand

Mutation

any change in the nucleotide sequence of DNA

Causes of mutations

Errors in DNA replication, radiation, chemicals, viruses inserting genetic material

Full name for DNA

Deoxyribonucleic Acid

Full name of RNA

Ribonucleic Acid

Mutation effects

Mutations can be good, bad, or result in no change depending on the type of change, where it occurs, if detected and fixed, and its effect on the organism

DNA Replication

the process of copying DNA so each new cell gets a full set of DNA

Transcription

the process of converting DNA into RNA in the nucleus

Translation

RNA → protein(polypeptide) in cytoplasm

Mutagen

Physical or chemical agents that can cause mutations.

Characteristics of a virus

They are energy-less, they are either DNA OR RNA, and replication is only by taking control of the host cell's synthetic machinery.

Virus replication steps

Entry, Uncoating, RNA synthesis by viral enzyme, Protein synthesis, RNA synthesis (other strand), Assembly, Exit.

Living organisms vs. viruses

Viruses sit on the fence between life and nonlife, exhibiting some but not all characteristics of living organisms.

Tobacco Mosaic Virus (TMV)

TMV was the reason for the creation of GMOs.

AIDS

AIDS stands for acquired immune deficiency syndrome, caused by the HIV (human immunodeficiency virus).

Retroviruses

A type of virus that includes Measles, HIV, and Coronavirus.

Reverse transcriptase

An enzyme that copies RNA to DNA.

Outbreak

A few thousand cases.

Epidemic

A disease affecting a country.

Pandemic

A worldwide disease outbreak.

Cellular differentiation

Cells become specialized in structure and function.

Gene Regulation

Certain genes are turned on and off in the process.

Gene Expression

A gene is turned on and transcribed into RNA, with information flowing from genes to proteins, genotype to phenotype.

Cloning

Reproductive cloning vs therapeutic cloning: Get an actual organism vs. growing a cell or organ.

Totipotent cell

Total potential that declines as they become more developed.

Embryonic Stem Cells

Can become anything.

Pluripotent cell

Partially developed.

Differentiated cell

Adult Stem Cells.

Regeneration

The regrowth of lost body parts in animals.

History of Cloning

A better breed of corn → A tadpole is cloned → The world's first test-tube baby → From embryo to ewe → Hello, Dolly.

Uses for cloned organisms

Farm animals, control animals for experiments, rare animals in danger of extinction.

Stem cell

Nature's template for all cells that can become any sort of cell or tissue in the body.

Adult stem cells

found in tissues like bone marrow

Stem cells in different culture conditions

can be manipulated to become different types of differentiated cells like blood cells, nerve cells, or heart muscle cells

Difference between embryonic and adult stem cells

Embryonic stem cells can become any type of cell in the body (pluripotent) and are found in early embryos. Adult stem cells can become only certain types of cells related to the tissue they're in and are found in developed tissues.

GMO

An organism that carries recombinant DNA is called a genetically modified (GMO) organism.

Recombinant DNA (rDNA)

A set of techniques for combining genes from different sources into a single DNA molecule.

Characteristics of a plasmid

Plasmids are small, circular DNA molecules that are separate from the much larger bacterial chromosome.

Plasmid function

Plasmids can easily incorporate foreign DNA (knock in a gene).

Plasmid uptake

Plasmids are readily taken up by bacterial cells (can move them from one bacterium to another).

Plasmid role

Plasmids then act as DNA carriers that move genes from one cell to another.

First genetically modified product

Human insulin was produced by genetically modified bacteria.

Company that produced first GM product

Eli Lilly and Company.

Disadvantages before genetic engineering of insulin

Before Humulin, insulin came from pigs and cows, which sometimes caused allergic reactions in humans because the animal insulin wasn't identical to human insulin. It was also costly and time-consuming to collect insulin from animals.

Advantages of the first GMO product (Humulin)

Humulin is identical to human insulin, so it causes fewer allergic reactions. It can be produced in large quantities quickly and safely using bacteria. It made insulin more available and affordable for people with diabetes.

Golden corn

GMO corn rich in vitamin A (from beta-carotene) to improve nutrition.

Pharm animals

Genetically modified animals that produce medicines or useful proteins for humans.

Human gene therapy

Seeks to treat disease by altering the genes of the afflicted person using a recombinant DNA procedure.

SCID

A fatal inherited disease caused by a single defective gene that prevents the development of the immune system.

Gene Therapy and SCID

Since 2000, gene therapy has successfully cured 22 children with inborn SCID.