Genetics 1.1

The blending theory of inheritance is the belief that inheritance works like the mixing of fluids such as paints, where traits from parents blend together in their offspring.

DNA is the molecule that encodes genetic information. The strings of four different chemical bases in DNA store genetic information in much the same way that strings of 0’s and 1’s store information in computer code.

The Native American Hopi tribe believed that planting a red kernel of maize would grow into a plant that also gave red kernels, and the same was true for blue, white, or yellow kernels. They thought of the kernel as a message to the gods in the Earth about the type of maize they hoped to harvest.

Gregor Mendel was an Austrian monk who discovered the laws of inheritance.

Mendel observed that there were roughly 3 purple-flowered plants for every 1 white-flowered plant.

An experimental organism is a species used in research to study biological processes, often because it has certain advantageous characteristics such as short generation times, ease of maintenance, or well-understood genetics.

Ronald Fisher proposed the multifactorial hypothesis, which states that continuously variable traits, such as human height, are controlled by multiple Mendelian genes.

The multifactorial hypothesis states that continuously variable traits are each controlled by multiple Mendelian genes.

Genetics is the study of genes, genetic variation, and heredity in living organisms.

Genetic analysis is the study of DNA, genes, and genetic variation to understand how they influence biological processes and traits.

In agriculture, genetics is applied to improve crop yields, enhance resistance to pests and diseases, and develop new plant varieties with desirable traits.

The double-helical structure of DNA, showing the sugar–phosphate backbone in blue and paired bases in brown.

Nucleotides in the mRNA that specifies an amino acid in a protein are called codons. For example, CGC specifies the amino acid arginine, AGC specifies serine, and so forth.

Contemporary research in genetics integrates past concepts with recent advances by using modern technologies to build on foundational discoveries, leading to new insights and applications in various fields.

A always pairs with T, and G always pairs with C.

The central dogma of molecular biology states that genes are made of DNA, which is transcribed to RNA molecules that serve as the template for protein synthesis.

The sequence of A, T, G, and C represents the coded information carried by the DNA molecule.

Additional pathways of genetic information flow include classes of RNA that do not code for proteins, instances in which mRNA is edited after transcription, and cases in which the information in RNA is copied back to DNA.

The bonding specificity is based on the complementary shapes and charges of the bases.

'Versuche über Pflanzen-Hybriden' is the title of Gregor Mendel's 1866 publication, which translates to 'Experiments on Plant Hybrids'.

Mendel's particulate theory of inheritance, published in 1866, proposed that inheritance is based on discrete units or 'particles' (now known as genes) that are passed from parents to offspring.

Gene sind die Partikel, die die Merkmale kontrollieren und von einer Generation zur nächsten intakt weitergegeben werden.

'Versuche über Pflanzen-Hybriden' was authored by Gregor Mendel.

The term 'genetics' was coined by British biologist William Bateson in 1905.

Somatische Zellen sind die Körperzellen einer Pflanze, die zwei Kopien des Gens enthalten, das die Blütenfarbe kontrolliert.

The artificial fertilizations were performed on ornamental plants to achieve new color variants.

In 1900, William Bateson read Mendel's 1866 paper on the hybridization of plant varieties and realized the importance of Mendel's laws of inheritance, leading him to become a proponent of Mendel's work.

Gameten sind Geschlechtszellen (Eizellen und Spermien), die nur eine Kopie des Gens enthalten.

Allele sind Genvarianten, die ein bestimmtes Merkmal, wie die Blütenfarbe, beeinflussen.

The purple and white circles signify the gene variants for purple vs. white flower color.

The '×' signifies a cross-pollination between the purple- and white-flowered plants.

Mendel proposed that the purple allele of the flower color gene is dominant to the white allele, such that a plant with one purple allele and one white allele would have purple flowers.

Mendel concluded that (1) genes behave like particles and do not blend together, and (2) one allele is dominant to the other.

The ratio of purple to white flowers in the second-generation hybrids is 3:1.

The traits Mendel studied were all controlled by single genes, which allowed him to discover the laws of inheritance more easily.

A purple-flowered pea plant results from a purple egg and a purple sperm.

Gametes carry one gene.

A purple-flowered pea plant results from one white gamete and one purple gamete.

A white-flowered pea plant results from a white egg and a white sperm.

Blending theory is the idea that hereditary fluids from parents mix together to produce offspring with traits that are a blend of both parents. Over many generations, this would result in a population where all members express the same average value of a trait.

Gregor Mendel was an Austrian monk who conducted experiments to understand the rules governing the transmission of traits from parent to offspring through hybridization among different varieties of pea plants.

The setting for Gregor Mendel's experiments was the monastery garden in the town of Brünn, Austria (now Brno, Czech Republic).

Transmission genetics is the study of the rules that govern the transmission of genetic information from parent to offspring within families.

Molecular-developmental genetics is the study of the transmission of genetic information from DNA to gene action within and between cells.

Mendel observed that the first hybrid generation of offspring from crossing a pea variety with purple flowers to one with white flowers all had purple flowers, just like one of the parents, indicating no blending.

Population-evolutionary genetics is the study of the transmission of genetic information over many generations within populations of organisms.

Nucleotides are the building blocks of DNA and RNA, each consisting of a sugar, a phosphate group, and one of four different bases (A, T, C, or G in DNA; A, U, C, or G in RNA).

William Bateson was a prominent British biologist who predicted that the exact determination of the laws of heredity would significantly change humanity's outlook on the world and its power over nature.

The central dogma of molecular biology is the flow of genetic information within cells from DNA to RNA to protein.

Messenger RNA (mRNA) carries information from DNA in the nucleus to the cytoplasm, where proteins are synthesized.

In 1958, Francis Crick introduced the phrase 'central dogma' to represent the flow of genetic information within cells from DNA to RNA to protein.

Genes reside on chromosomes and are made of DNA. They encode proteins that conduct the basic enzymatic work within cells.

A regulatory DNA element is a sequence in the DNA, such as 'GGGCCC', to which a regulatory protein binds to control the transcription of a gene.

The RNA polymerase complex binds to a specific site on the DNA to initiate the transcription of a protein-coding gene.

The discovery of the double-helical structure of DNA was a watershed moment for biology, providing a fundamental understanding of how genetic information is stored.

'Cracking the genetic code' refers to the discovery of how sequences of DNA encode the information necessary to synthesize proteins, achieved by geneticists and chemists between 1961 and 1967.

William Bateson, a British zoologist and evolutionist, introduced the term 'genetics' for the study of inheritance and promoted Mendel’s work.

Mendelism, based on Mendel’s laws of inheritance, became the organizing principle for much of biology after 1900.

In 1865, Gregor Mendel showed that traits are controlled by discrete factors now known as genes.

In 1903, Walter Sutton and Theodor Boveri hypothesized that chromosomes are the hereditary elements.

DNA replication is the process by which a copy of the DNA is produced, enabling each of the two daughter cells that result from cell division to have a complete copy of all the DNA in the parent cell.

Transcription is the process of RNA synthesis from a DNA template, where the sequence of base pairs in a gene (DNA) is copied to an RNA molecule.

The one-gene–one-enzyme hypothesis, proposed by Edward Tatum and George Beadle in 1941, states that genes encode enzymes that perform metabolic functions within cells.

Messenger RNA (mRNA) is a class of RNA molecules made by transcription that serves as the template for protein synthesis.

Edward Tatum and George Beadle proposed the one-gene–one-enzyme hypothesis in 1941.

Translation is the process of synthesizing proteins by decoding the information in the specific sequence of bases in the mRNA into the sequence of amino acids that compose a protein.

Tatum and Beadle used bread mold (Neurospora crassa) as their experimental organism to demonstrate the one-gene–one-enzyme hypothesis.

A codon is a set of three consecutive bases in mRNA that specifies a particular amino acid to be incorporated into a protein during translation.

In the pea plant, there is a gene that encodes an enzyme required to make the purple pigment in the cells of a flower.

They offered the first compelling experimental evidence that genes are made of deoxyribonucleic acid (DNA). They showed that DNA extracted from a virulent strain of bacteria carried the necessary genetic information to transform a nonvirulent strain into a virulent one.

They confirmed that genes are made of deoxyribonucleic acid (DNA), supporting the findings of Oswald Avery, Colin MacLeod, and Maclyn McCarty.

The molecular structure of DNA is in the form of a double helix—two strands of DNA wound side-by-side in a spiral. The sides of the ladder are made of sugar and phosphate groups, and the rungs are made of four bases: adenine (A), thymine (T), guanine (G), and cytosine (C).

The four bases are adenine (A), thymine (T), guanine (G), and cytosine (C).

Adenine in one strand is always paired with thymine in the other by a double hydrogen bond, whereas guanine is always paired with cytosine.

The central dogma describes the flow of genetic information in cells from DNA to RNA to protein. It involves DNA replication, transcription of DNA into RNA, and translation of RNA into protein.

DNA replication is the process by which a DNA molecule makes a copy of itself. This involves unwinding the double helix and using each strand as a template to synthesize a new complementary strand.

Transcription is the process by which a segment of DNA is copied into RNA by the enzyme RNA polymerase. This RNA can then be used to produce proteins.

Translation is the process by which messenger RNA (mRNA) is decoded by the ribosome to produce a specific protein. This involves the assembly of amino acids in the order specified by the mRNA.

Messenger RNA (mRNA) is a type of RNA that carries genetic information from DNA to the ribosome, where it specifies the amino acid sequence of the protein products of gene expression.

Adenine is paired with thymine in the DNA double helix.

Cytosine is paired with guanine in the DNA double helix.

The phosphate group has a phosphorous atom bonded with four oxygen atoms, one of which is bonded to the carbon atom of the methylene group of the sugar molecule.

The bases in one strand are connected to bases in the other strand by hydrogen bonds.

DNA is a double helix in which the nucleotide bases of one strand are paired with those of the other strand. Adenine always pairs with thymine, and guanine always pairs with cytosine.

François Jacob and Jacques Monod discovered that genes have regulatory elements that control gene expression, determining whether a gene is turned on or off.

Regulatory elements are specific DNA sequences to which a regulatory protein binds and acts as either an activator or repressor of the expression of the gene.

The neutral theory of molecular evolution, proposed by Motoo Kimura in 1968, suggests that most evolutionary changes at the molecular level are caused by random genetic drift of mutant alleles that are selectively neutral.

Fred Sanger, Walter Gilbert, and Allan Maxam invented methods for determining the nucleotide sequences of DNA molecules in 1977.

Christiane Nüsslein-Volhard and Eric F. Wieschaus defined the complex of genes that regulate body plan development in Drosophila in 1980.

Francis Collins and Lap-Chee Tsui discovered the gene causing cystic fibrosis in 1989.

The first genome sequence of a living organism, Haemophilus influenzae, was published in 1995.

Andrew Fire and Craig Mello discovered a mechanism of gene silencing by double-stranded RNA in 1998.

The first genome sequence of an animal, Caenorhabditis elegans, was published in 1998.

The sequence of the human genome was first published in 2001.

Elizabeth H. Blackburn, Carol W. Greider, and Jack W. Szostak won the Nobel Prize in 2009 for their discovery of how chromosomes are protected by telomeres and the enzyme telomerase.

John Gurdon and Shinya Yamanaka won the Nobel Prize in 2012 for their discovery that just four regulatory genes can convert adult cells into stem cells.

Thomas H. Morgan demonstrated in 1910 that Mendel’s genes are located on chromosomes, proving the chromosome theory of inheritance.

Walter Sutton and Theodor Boveri independently proposed the chromosome theory of inheritance in 1903.

Genetics

The Hardy–Weinberg law, the foundation for population genetics.

Thomas H. Morgan

A genetic linkage map of the Drosophila X chromosome, the first genetic map.

Ronald Fisher, founding the field of quantitative genetics.

That crossing over is the cause of recombination.

The one-gene–one-polypeptide hypothesis.

Oswald Avery, Colin MacLeod, and Maclyn McCarty.

Bacterial conjugation.

Mobile elements (transposons) that move from one place to another in the genome.

Simple rules for the relative amounts of A, C, G, and T.

That DNA is the molecule that encodes genetic information.

James Watson and Francis Crick, using data produced by Rosalind Franklin and Maurice Wilkins.

The semiconservative nature of DNA replication.

That Down syndrome resulted from an extra copy of the 21st chromosome.

That enzyme levels in cells are controlled by feedback mechanisms.

Marshall Nirenberg, Har Gobind Khorana, Sydney Brenner, and Francis Crick.