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Strange Cat Things

December 3, 2018

Cats are one of the most popular choices as human friends, and I absolutely adore them! I hope to have a feline friend in the future and hopefully, you will too if you don’t have one already. Among all the cute actions that these creatures engage in daily, there are some anomalies that make their human friends ponder. These fun facts may answer a question or two you’ve had and enlighten you with the uniqueness and awesomeness of cats.

The cats we have in our homes are really similar to wild cats!
Compared to dogs, cats have been domesticated for only half as long and still engage in behaviors similar to wild, big cats such as lions and tigers. Their genes have not changed much from that of wildcats, except for one distinguishing factor: the coat patterns seen on the tabby cat (“Cats Domesticated Themselves, Ancient DNA Shows,” 2018).

Cats cannot taste sweetness. 
Like humans, cats are able to taste saltiness, bitterness, sourness, and umami! The genes Tas1r2 and Tas1r3 allow sweet tasting in mammals by encoding sweet sensing receptors. Cats have both of these genes, but their Tas1r2 gene, however, is a pseudogene, or nonfunctional copies of a functional gene (Li, Li, Wang, Bayley, Cao, Reed, Bachmanov, Huang, Legrand-Defretin, Beauchamp, and Brand, 2006).

Why do cats kill unbelievable amounts of mice and birds?
As natural-hunters, cats still carry unstoppable instincts that they’ve had thousands of years ago. Female cats are also found to engage in hunting more often to teach their young how to acquire food and feed (Palermo, 2013).

Cats will bite in response to being overstimulated, not because they hate you!
Overstimulation typically occurs in attention-seeking, friendly cats. When these felines are continuously being pet, it appears that there can be a buildup of stress for these animals leading to aggressive behaviors. Cats may give some warning signs before their impending aggression such as a continuous, whipping tail, flattened ears, and a tense body (“Overstimulation in Cats,” n.d.).

Cats meow only to communicate with humans!
Meows are usually found in kittens that need to communicate with their mother. However, communication between older cats consists of growling and hissing. Meowing is exclusively used by felines to tell their humans if they may be hungry, stressed, or needing attention (“Cats and Excessive Meowing,” n.d.).

Cats sleep a lot, but why?
Cats sleep up to 16 hours a day – that’s 67% of the day! This is because they need energy for hunting-like behaviors such as pouncing and chasing (Cespedes, n.d.).

Cats are crepuscular, so their schedules are completely different from humans.
They are most active at dawn and dusk, and often nap during the day while basking in the sun (Cespedes, n.d.). Though this is their natural schedule, cats may adjust their sleeping to fit their owner’s schedule.

Why do cats bury their excretions?
Burying waste is an instinct that cats have in order to mark their territory and avoid attention from predators (Melina, 2011). Their excretions have unique pheromones, making it possible for other cats to differentiate it from their own waste.

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References

Cats and Excessive Meowing. (n.d.). Retrieved from https://pets.webmd.com/cats/guide/cats-excessive-meowing#1

Cats Domesticated Themselves, Ancient DNA Shows. (2018, April 24). Retrieved from https://news.nationalgeographic.com/2017/06/domesticated-cats-dna-genetics-pets-science/

Cespedes, Y. (n.d.). Retrieved from https://www.petmd.com/cat/behavior/evr_ct_why_do_cats_sleep_so_much

Li, X., Li, W., Wang, H., Bayley, D. L., Cao, J., Reed, D. R., Bachmanov, A. A., Huang, L., Legrand-Defretin, V., Beauchamp, G. K., … Brand, J. G. (2006). Cats lack a sweet taste receptor. The Journal of nutrition, 136(7 Suppl), 1932S-1934S.

Melina, R. Why Do Cats Bury Their Poop? (2011, March 23). Retrieved from https://www.livescience.com/33147-why-do-cats-bury-their-poop.html

Overstimulation in Cats. (n.d.). Retrieved from http://www.treehouseanimals.org/site/PageServer?pagename=caring_ccg_overstimulation

Palermo, E. Why Do Cats Bring Home Dead Animals? (2013, March 29). Retrieved from https://www.livescience.com/34471-cats-dead-animals.html

Surprising Things You Never Knew About Your Cat. (2015, December 03). Retrieved from https://news.nationalgeographic.com/2015/12/151203-cats-animals-science-communication-pets/

 

 

 

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Anna Ho
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Anna is a pre-medicine Neuroscience undergraduate at Georgia Tech. In her free time, she enjoys watching anime, drinking bubble tea, and spending time on her piano. She is also obsessed with cats.

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.