The Science and History of Genetics Quiz

Answer: Pea

The humble pea plant is the source of knowledge from which the discipline of genetics has developed. It highlights the great partnership between botany and medical science in that not only do plants provide useful drugs, but, they form the foundation of our genetic knowledge. What Herr Mendel discovered was that certain traits, in this case the colour of the pea plant, were either dominant or recessive (this is a bit simplistic, as other traits can be co-dominant). Mendel observed that when smooth yellow peas were crossed with wrinkly green peas, all the offspring in the F1 (first filial generation) were smooth and yellow.

His experiment continued with the crossing of the F1 pea plants and this time 75% were smooth and yellow and 25% were wrinkly green. Voila, the birth of modern genetics. Unfortunately for Mendel, his experiments and results were largely ignored for the best part of 35 years.

Answer: Punnett Square

The Punnett square was devised by the British geneticist and zoologist, Reginald C. Punnett. The genetic diagram is extremely useful in ascertaining the probabilities of certain conditions being inherited by offspring.
There are some limitations to the method however and the common example is the sex linkage and (XY) genotype of males. In the inheritance of sex, a gene is passed from both the mother (XX) and the father (XY) to create a pair. Humans nearly always have two copies of each gene, except for the XY genotype of males. The implication of this is that conditions caused by the X chromosome are going to more likely affect males as they only have one copy of the gene. Thus, if the X chromosome is defective the male will develop the trait. With females, who have two copies of the gene on X chromosomes, the trait will only be shown if BOTH genes are defective.
This has phenotypic consequences whereby some conditions statistically affect a greater proportion of males than females. Such conditions include the various types of colour blindness.

Answer: Alleles

In humans, an example of a diploid organism, there are two alleles which are crucially important in determining every single phenotypic trait. Behind hair colour, eye colour and even subtle mannerisms, lies genetics and alleles. Gametes (sperm and ova) contain half the genetic information of a somatic (body) cell and is known as a haploid cell. So, a sperm cell contains 23 chromosomes which is a half of the 46 chromosomes in a cheek lining cell for instance. On each of these chromosomes will be alleles and it is random chance which of the two alleles for a particular gene the offspring will receive from the father and also from the female egg cell.

This random inheritance, which can be displayed in a Punnett square, introduces variation.

Answer: Meiosis

The formation of the sex cells, or gametogenesis, results in offspring that genetically differ from the parental organism when the process of fertilisation has occurred.
Meiosis and mitosis are two forms of nuclear division* and whilst both are in many ways similar, there are some important differences. An example of such a difference is that in meiosis (part I of II) there is the formation of a bivalent. A bivalent is a pair of homologous chromosomes that are of equal length, with a centromere and genes in the same locations on each chromosome.
Another difference being the result of mitosis is two daughter cells being genetically identical to the mother cell whilst the result of meiosis is four daughter cells that are NOT genetically identical to the mother cell.

*A common misconception is that meiosis and mitosis are forms of cell division. Cell division itself cannot take place without cytokinesis (division of cytoplasm) and it is therefore more correctly termed nuclear division. Id est, the nuclear material divides.

Answer: Substitution

A frame shift mutation results when a nitrogenous base is deleted or added to the genetic code of an organism. A frame shift is a movement of all bases after the point of interruption, so take the completely made up genetic base sequence "THE DOG BIT THE CAT" as an example. The basics of DNA state that three nitrogenous bases form a codon (in our example THE, DOG, CAT or BIT) and one codon codes for an amino acid. It only takes one faulty codon to code for an inappropriate amino acid and a plethora of conditions can arise. A faulty codon usually develops through the different types of genetic mutation.

Take the genetic mutation of deletion; a process whereby a nitrogenous base is as you'd expect, deleted. Before the deletion the DNA sequence would be "THE DOG BIT THE CAT". If the base "I" is deleted the sequence will look as such:

"THE DOG BTT HEC AT..."

As can be seen the message has been completely messed up and this is a frame shift! You can see that "THE" and "DOG" have been unaffected but from the codon that included the base "I" onwards it will be highly unlikely that they will now code for the correct amino acid. This also happens when a base is added (addition mutation).

With a substitution mutation one nitrogenous base is changed to another. So, again take "THE DOG BIT THE CAT" and let us substitute "O" for "Q". The new code will be "THE DQG BIT THE CAT" and as can be seen only one codon (in this case "DOG") will be affected. "BIT", "THE" and "CAT" do not undergo a frame shift mutation. It is suggested that mutations that end up in frame shifts are more detrimental to an organism than substitution. Indeed it is possible that the DNA of an organism could be mutated by substitution and there is no effect at all!

Answer: Hardy - Weinberg

There are two parts to the Hardy-Weinberg equation and equilibrium and they are:

1) p^2 + 2pq + q^2 = 1
2) p + q = 1

The second equation is more of a general formula that states that the frequency of a dominant allele (p) added to the frequency of the recessive allele (q) equals unity. Unity (or the number 1) in this case represents the entire gene pool or a part of the gene pool that is under investigation. The first equation which is more formally recognised as the Hardy-Weinberg equation quantifies the frequencies of alleles in a population. The total population (1) is equal to the frequency of the dominant homozygote (p^2) plus the frequency of the heterozygote (2pq) plus the frequency of the the recessive homozygote (q^2). For clarification a homozygote is where both of the alleles are the same and a heterozygote is where the two alleles differ.

The Hardy-Weinberg equilibrium states that the proportion of different alleles, and thus different genotypes, in a population remains constant from generation to generation. (This is one of the many standard definitions that can be found in biological and medical textbooks and journals around the world). In general this proposed equilibrium is only applicable when the population in question is large and that there is no immigration of the population. There are a few other conditions but these two are the most important.

Answer: Finch

The two men that were instrumental in the development of genetics and evolution died within two years of each other. Charles Darwin died in 1882 and Gregor Mendel died shortly after in 1884. As these dates would suggest, the science of genetics hadn't really taken off and very little was known about it. What little was known was the work of Gregor Mendel and that was blatantly ignored. So, when Charles Darwin came to describing concepts such as speciation and development over the generations within populations it was really the description of genetic changes and inheritance. Briefly, what Charles Darwin theorised was there is always an overproduction of offspring and due to the number of individuals in the population of a species staying roughly constant many individuals would die without reproducing.

The remaining organisms all compete with one another to survive and this includes the competition for things such as nutrients and water and in the case of plants, light. Only a few organisms would survive to a point where they could breed and the most important point of all; the offspring would demonstrate variation. Due to this variation, which we now know is due to genetics, some amongst the offspring would be better adapted to suit certain conditions and by extension, be able to survive.

The offspring that did not inherit the advantageous traits would be less likely to survive and breed. Thus, the "fittest" survive which is where the term "survival of the fittest" stems from. Darwin then made the critical observation that those who were fit enough to survive would pass on the advantageous traits to the next generation and that over many generations so many variations will take place that a new species will form.

Answer: Jean-Baptiste Lamarck

The most important concept of Lamarck's theory is that the environment has an effect on organic organisms such that the surroundings elicit changes in the organism. Furthermore, he stated that life is orderly which allows it to function effectively. This was hypothesised in French by the term "la force qui tend sans cesse à composer l'organisation" which suggests that there is a perpetual force that tends towards order.
Fundamentally Lamarck suggested that through using parts of the anatomy the said part improves and that through under use, the anatomical part diminishes in prominence. This can be illustrated by the giraffe and how it obtains its food on branches of high trees. If Lamarck were to be believed, the giraffes that were too small to reach the leaves would have to continuously stretch to reach them. As a result of constantly using the body part, in this case the neck, it would grow, id est the neck would become longer so that the giraffe could eat. These changes are then passed on to the offspring.

Despite Lamarck's theories being considered ultimately incorrect he still holds a strong claim of being the father of evolution. Lamarck certainly made his evolutionary proposals before Darwin and subsequently a statue in Paris entitles Lamarck the "Fondateur de la doctrine de l'évolution" or in English, "Founder of the doctrine of evolution".

Emil Adolf von Behring, Karl Landsteiner and Thomas Hunt Morgan are all 20th century Nobel Laureates in the medicine and physiology category. von Behring was the first winner of this award (1901) and he was recognised for his work in the science of diphtheria. Karl Landsteiner won the Nobel Prize in 1930 for developing the modern ABO blood group system based on antigens and antibodies. American geneticist Thomas Hunt Morgan received the award in 1933 for his work on chromosomes and how they are involved in inheritance.

Answer: Codominance

In diploid organisms, like humans, there are two copies of each gene that are called alleles. Often one of the genes will take priority over the other and this is the case if one of the genes is dominant and the other recessive. When this happens only the phenotype that is coded for by the dominant allele will become a trait.

However in some cases, including the genetics of blood groups, more than one allele is said to be dominant. If both of these different dominant alleles are inherited then the offspring is said to be codominant for a trait. If we use the ABO blood group system as an example.

There are three alleles that code for blood groups and they are A, B and i where allele A as you'd expect codes for group A, allele B for group B and allele i codes for group O. Alleles A and B are dominant to allele i and this can be seen just by looking at whether the letter representing the allele is upper or lower case; upper representing dominant and lower representing recessive. Due to both allele A and allele B being dominant they both will be expressed if they are inherited. So, if the offspring inherited one allele A and one allele B, you would expect the child to either be blood group A or blood group B depending on which is dominant, but, because they are both dominant the gene AB will result in the child being blood group AB.

This is codominance!

Answer: Taxonomy

I actually find taxonomy quite fun and it takes a committed nerd to say something like that! There are many subtleties to this science of classification such as the US having a slightly different set of kingdoms to the UK and a few other commonwealth nations. The US have six kingdoms which are Animalia, Archaea, Eubacteria, Fungi, Plantae and Protista whilst the UK have five kingdoms which are Animalia, Fungi, Plantae, Prokaryota and Protista. The difference stems from the British not elevating the two sub-divisions of the Kingdom Prokaryota (Archaea and Eubacteria) to kingdom status.
In taxonomy there is a series of ranks which aid classification and another subtlety of the science is that there is a slightly different system of botanical classification to zoological. The zoological system of classification from the top of the hierarchy down is kingdom, phylum, class, order, family, genus and species. In the botanical classification system the term phylum isn't implemented and the term division is used instead.

I hope you enjoyed this quiz and thanks for playing!