Darwin's Second Quiz Answers Explained

Question 1: What percentage of the human genome is shared with that of chimpanzees?

Options: A) 82% B) 88% C) 95% D) 99%

Answer: D) 99% 

Explanation: Ever since researchers sequenced the chimp genome in 2005, they have known that humans share ~99% of their DNA with chimpanzees, making them our closest living relative. In fact, there is a second species that is this closely genetically related to humans: bonobos. The ancestor of humans split with the common ancestor of bonobos and chimps between 4 and 7 million years ago in Africa. Recent research is going into finding out whether this last common ancestor between these 3 species looked and acted more like a bonobo, a chimpanzee, or something else. 

Question 2: From the following diseases, select all monogenetic disorders (those which can be inherited based on a single gene).

Options: A) Sickle Cell Anaemia B) Rheumatoid Arthritis C) Alzheimer’s Disease D) Marfan Syndrome E) Fragile X Syndrome 

Answers: A) Sickle Cell Anaemia D) Marfan Syndrome E) Fragile X Syndrome

Explanation:

Sickle cell anaemia

Sickle cell anaemia is a common inherited blood disorder that is most prevalent among Africans. It is caused by a mutation in the haemoglobin-ß gene, which causes haemoglobin molecules to stick to one another and form long, rod-like structures. Haemoglobin is an essential Oxygen-transport protein found in red blood cells. Red blood cells with normal haemoglobin are smooth and round and glide through blood vessels. In people with sickle cell disease, red blood cells become stiff and assuming a sickle shape, causing blockages and damaging vital organs and tissue. Blockages in blood vessels increase the risk of lung tissue damage, strokes and acute pain episodes. Sickle cell anaemia is inherited in an autosomal recessive manner. 

When we think about genetic disease, it is interest to ask ourselves why and how the disease-marking alleles remain in a population. Evolutionary, it would make sense for these to be eliminated from a population, as they result in un-favourable traits. However, individuals who are carriers for the sickle cell gene have some protective advantage against malaria. As a result, the frequencies of sickle cell carriers are high in malaria-endemic areas.  

Marfan Syndrome

Marfan Syndrome Marfan syndrome is a disease of the connective tissue caused by a mutation in the gene encoding an extracellular matrix protein called fibrillin. People with Marfan syndrome tend to be tall and thin, with long arms, legs, fingers and toes. They also typically have flexible joints and scoliosis. The most serious complications involve the heart and aorta, with an increased risk of mitral valve prolapse and aortic aneurysm. Marfan syndrome is inherited in an autosomal dominant manner. 

Fragile X Syndrome

Fragile X syndrome is a genetic condition that causes a range of developmental problems including learning difficulties and cognitive impairment. Fragile X syndrome is caused by an expansion of over 200 CGG repeats on the FMR1 gene on the X chromosome. The inheritance pattern is X-linked dominant and the symptoms tend to be more severe for men suffering from it.  

Question 4: The genome editing technology, CRISPR, stands for:

Options: 

A) Cas9-Regulated Incision for Supra-Phenotypic Regeneration 

B) Clustered Regularly Interspaced Short Palindromic Repeats 

C) Coding Region In Sperm Protein Revalidation

D) Chromosome Reduced Indicative Sickle Protein Release

Answer: B) Clustered Regularly Interspaced Short Palindromic Repeats

Explanation: 

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a family of DNA sequences that form part of the bacterial immune system against foreign genetic elements such as plasmids and phages. CRISPR, together with the nuclease Cas9, has been adapted to create a genome editing technology. Scientists are attempting to further develop CRISPR-Cas9, so that in the near future it could be used for gene therapy and as a powerful diagnostic tool.

Question 6: Which of the following is correct regarding blood types?

Options: A) The A allele is dominant over B and O, and B is dominant over O

B) The O allele is dominant over A and B, which are both recessive

C) The A and B alleles are dominant, the O allele is recessive

D) The B allele is dominant over O and A, and O is dominant over A 

Answer: C) The A and B alleles are dominant, the O allele is recessive

Explanation: 

Question 8: Gregor Mendel, known by many as the father of genetics, observed the inheritance patterns of what species?

Options: A) Rats B) Frogs C) Fruit Flies D) Peas

Answer: D) Peas 

Explanation: Gregor Mendel was a Czech monk who performed cross-breeding experiments between different types of pea plants that he grew in his garden. In particular, he was determined to find an explanation to how pea plants inherited particular characteristics, namely plant height, colour, pod and seed shape, and flower position. He determined that, upon sexual reproduction, an offspring receives two sets of information, one from each parent, that each define one particular characteristic in appearance. He also concluded that some units of information were dominant above others. These sets of information are now known as alleles. Mendel's experimental findings set the scene for modern genetics, before anyone even knew what a gene was. 

See Gallery for more information of Mendel's pea plant experiments. 

Question 10: An organism's observable characteristics are known as its:

Options: A) Genotype B) Phenotype C) Gene Expression D) Allele

Answer: B) Phenotype