Carl Correns
Encyclopedia
Carl Erich Correns was a German
botanist and geneticist
, who is notable primarily for his independent discovery of the principles of heredity
, and for his rediscovery of Gregor Mendel
's earlier paper on that subject, which he achieved simultaneously but independently of the botanists Erich Tschermak von Seysenegg and Hugo de Vries
.
By a quirk of history Correns was a student of Nageli, a renowned botanist with whom Mendel corresponded about his work with peas, but who failed to understand how significant Mendel's work was. Tschermak was a grandson of a man who taught botany to Mendel, during Mendel's student days in Vienna.
. Orphaned at an early age, he was raised by an aunt in Switzerland
. He entered the University of Munich
in 1885. While there, he was encouraged to study botany by Karl Nägeli
, a botanist whom Mendel corresponded with on the subject of his pea plant experiments. After completing his thesis, Correns became a tutor at the University of Tübingen and in 1913 he became the first director of the newly founded Kaiser Wilhelm Institute for Biology in Berlin-Dahlem.
. He also discovered cytoplasmic inheritance
, an important extension of Mendel's theories, which demonstrated the existence of extra-chromosomal factors on phenotype. Most of Correns' work went unpublished however, and was destroyed in the Berlin bombings of 1945.
plant experiments that Mendel carried out, not being aware of the pea plant results. Correns published his first paper on January 25, 1900, which cited both Charles Darwin
and Mendel, though without fully recognising the relevance of genetics
to Darwin's ideas. In Correns' paper, "G.Mendel's Law Concerning the Behavior of the Progeny of Racial Hybrids", he restated Mendel's results and his law of segregation and law of independent assortment.
inheritance, he undertook experiments with the four o'clock
(Mirabilis jalapa) to investigate apparent counterexamples to Mendel's laws in the heredity of variegated (green and white mottled) leaf color. Correns found that, while Mendelian traits behave independently of the sex of the source parent, leaf color depended greatly on which parent had which trait. For instance, pollinating an ovule
from a white branch with pollen from another white area resulted in white progeny, the predicted result for a recessive gene. Green pollen used on a green stigma resulted in all green progeny, the expected result for a dominant gene. However, if green pollen fertilized a white stigma, the progeny were white, but if the sexes of the donors were reversed (white pollen on a green stigma), the progeny were green.
This non-mendelian inheritance
pattern was later traced to a gene
named iojap which codes for a small protein required for proper assembly of the chloroplast
ribosome
. Even though iojap assorts according to Mendel's rules, if the mother is homozygous recessive
, then the protein is not produced, the chloroplast ribosomes fail to form, and the plasmid becomes non-functional because the ribosomes cannot be imported into the organelle
. The progeny could have functional copies of iojap, but since the chloroplasts come exclusively from the mother in most angiosperms, they would have been inactivated in the previous generation, and so will give white plants. Conversely, if a white father is paired with a green mother with functional chloroplasts, the progeny will only inherit functional chloroplasts, and will thus be green. In his 1909 paper, he established variegated leaf color as the first conclusive example of cytoplasmic inheritance
.
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
botanist and geneticist
Geneticist
A geneticist is a biologist who studies genetics, the science of genes, heredity, and variation of organisms. A geneticist can be employed as a researcher or lecturer. Some geneticists perform experiments and analyze data to interpret the inheritance of skills. A geneticist is also a Consultant or...
, who is notable primarily for his independent discovery of the principles of heredity
Heredity
Heredity is the passing of traits to offspring . This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause some species to evolve...
, and for his rediscovery of Gregor Mendel
Gregor Mendel
Gregor Johann Mendel was an Austrian scientist and Augustinian friar who gained posthumous fame as the founder of the new science of genetics. Mendel demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance...
's earlier paper on that subject, which he achieved simultaneously but independently of the botanists Erich Tschermak von Seysenegg and Hugo de Vries
Hugo de Vries
Hugo Marie de Vries ForMemRS was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation...
.
By a quirk of history Correns was a student of Nageli, a renowned botanist with whom Mendel corresponded about his work with peas, but who failed to understand how significant Mendel's work was. Tschermak was a grandson of a man who taught botany to Mendel, during Mendel's student days in Vienna.
Early life and education
Carl Correns was born September 1864 in MunichMunich
Munich The city's motto is "" . Before 2006, it was "Weltstadt mit Herz" . Its native name, , is derived from the Old High German Munichen, meaning "by the monks' place". The city's name derives from the monks of the Benedictine order who founded the city; hence the monk depicted on the city's coat...
. Orphaned at an early age, he was raised by an aunt in Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
. He entered the University of Munich
Munich
Munich The city's motto is "" . Before 2006, it was "Weltstadt mit Herz" . Its native name, , is derived from the Old High German Munichen, meaning "by the monks' place". The city's name derives from the monks of the Benedictine order who founded the city; hence the monk depicted on the city's coat...
in 1885. While there, he was encouraged to study botany by Karl Nägeli
Karl Wilhelm von Nägeli
Karl Wilhelm von Nägeli was a Swiss botanist. He studied cell division and pollination, but became known as the man who discouraged Gregor Mendel from further work on genetics.-Birth and education:...
, a botanist whom Mendel corresponded with on the subject of his pea plant experiments. After completing his thesis, Correns became a tutor at the University of Tübingen and in 1913 he became the first director of the newly founded Kaiser Wilhelm Institute for Biology in Berlin-Dahlem.
Key experiments and findings
Carl Correns conducted much of the foundational work for the field of genetics at the turn of the 20th century. He rediscovered and independently verified the work of Mendel in a separate model organismModel organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
. He also discovered cytoplasmic inheritance
Extranuclear Inheritance
Extranuclear inheritance is the transmission of genes that occur outside the nucleus. It is found in most eukaryotes and is commonly known to occur in cytoplasmic organelles such as mitochondria and chloroplasts or from cellular parasites like viruses or bacteria .- Extranuclear Inheritance of...
, an important extension of Mendel's theories, which demonstrated the existence of extra-chromosomal factors on phenotype. Most of Correns' work went unpublished however, and was destroyed in the Berlin bombings of 1945.
Rediscovery of Mendel
In 1892, while at the University of Tübingen, Correns began to experiment with trait inheritance in plants. He focused mainly on the hawkweedHawkweed
Hawkweed refers to any species in the very large genus Hieracium and its segregate genus Pilosella, in the sunflower family ....
plant experiments that Mendel carried out, not being aware of the pea plant results. Correns published his first paper on January 25, 1900, which cited both Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
and Mendel, though without fully recognising the relevance of genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
to Darwin's ideas. In Correns' paper, "G.Mendel's Law Concerning the Behavior of the Progeny of Racial Hybrids", he restated Mendel's results and his law of segregation and law of independent assortment.
Cytoplasmic inheritance
After rediscovering Mendel's laws of heredity, which apply to chromosomalChromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
inheritance, he undertook experiments with the four o'clock
Mirabilis jalapa
Mirabilis jalapa is the most commonly grown ornamental species of Mirabilis, and is available in a range of colours. Mirabilis in Latin means wonderful and Jalapa is a town in Mexico...
(Mirabilis jalapa) to investigate apparent counterexamples to Mendel's laws in the heredity of variegated (green and white mottled) leaf color. Correns found that, while Mendelian traits behave independently of the sex of the source parent, leaf color depended greatly on which parent had which trait. For instance, pollinating an ovule
Ovule
Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center...
from a white branch with pollen from another white area resulted in white progeny, the predicted result for a recessive gene. Green pollen used on a green stigma resulted in all green progeny, the expected result for a dominant gene. However, if green pollen fertilized a white stigma, the progeny were white, but if the sexes of the donors were reversed (white pollen on a green stigma), the progeny were green.
This non-mendelian inheritance
Non-mendelian inheritance
Non-Mendelian inheritance is a general term that refers to any pattern of inheritance in which traits do not segregate in accordance with Mendel’s laws. These laws describe the inheritance of traits linked to single genes on chromosomes in the nucleus. In Mendelian inheritance, each parent...
pattern was later traced to a gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
named iojap which codes for a small protein required for proper assembly of the chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
ribosome
Ribosome
A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....
. Even though iojap assorts according to Mendel's rules, if the mother is homozygous recessive
Recessive
In genetics, the term "recessive gene" refers to an allele that causes a phenotype that is only seen in a homozygous genotype and never in a heterozygous genotype. Every person has two copies of every gene on autosomal chromosomes, one from mother and one from father...
, then the protein is not produced, the chloroplast ribosomes fail to form, and the plasmid becomes non-functional because the ribosomes cannot be imported into the organelle
Organelle
In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....
. The progeny could have functional copies of iojap, but since the chloroplasts come exclusively from the mother in most angiosperms, they would have been inactivated in the previous generation, and so will give white plants. Conversely, if a white father is paired with a green mother with functional chloroplasts, the progeny will only inherit functional chloroplasts, and will thus be green. In his 1909 paper, he established variegated leaf color as the first conclusive example of cytoplasmic inheritance
Extranuclear Inheritance
Extranuclear inheritance is the transmission of genes that occur outside the nucleus. It is found in most eukaryotes and is commonly known to occur in cytoplasmic organelles such as mitochondria and chloroplasts or from cellular parasites like viruses or bacteria .- Extranuclear Inheritance of...
.