BIO 101 Spring 2020: Lactose Persistence Genetics PowerPoint Project

This PowerPoint project delves into the genetics of lactose persistence, a beneficial mutation affecting the lactase gene. It begins with an introduction to the central dogma, explaining how the lactase enzyme is synthesized. The project then examines the lactase gene locus, the structure of the faulty lactase gene, and how mutations in the enhancer region lead to continual lactase production, resulting in lactose persistence. The presentation explores the pathways of mutant and normal protein products, their effects at cellular, tissue/organ, and organism levels. It also covers the inheritance of the mutated gene and its impact on life expectancy, highlighting the evolutionary advantages of lactose persistence and the absence of required treatment. The project includes citations of the sources used.

GENETICS POWERPOINT
PROJECT ON LACTOSE
PERSISTENCE

Introduction to lactose persistence
• Central dogma in molecular work for biologists and geneticists is the basic process
that describes the formation of a specific protein from it’s specific DNA through
transcription to RNA. Lactase is a typical enzyme which goes through the process of
transcription and translation for its synthesis. Infants always make the enzyme
lactase which enables them to digest the lactose sugar in milk from the mother.
• This gives simpler molecules of monosaccharides called galactose and glucose
which is easily absorbed into the baby’s system. As soon as weaning period of the
child is reached, most people stops producing lactase since at that period, they have
already left drinking milk.
• Consumption of milk when lactase enzyme is nowhere leads to formation of gas,
diarrhea, cramps and bloating. This is because the body cannot breakdown lactose
and hence bacteria in the intestines are left to perform that work and feed on the
lactose. Mutations in the enhancer region of lactase gene leads to the continual
turning on of the gene hence leading to the continual production of lactase even in
adults hence lactase persistence (Ségurel and Bon 298).

Lactase gene locus
https://ghr.nlm.nih.gov/gene/LCT#location
• The gene together with its enhancer responsible for
the synthesis of lactase enzyme is described by 2q21.3
according to the cytogenetic location.
• It simply means that this gene is found in
chromosome number 2 at the long arm (q) at the exact
position of 21.3 on that particular arm (Leseva 13).

Description of faulty lactase gene and change in protein
synthesis
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=imgres&cd=&cad=rja&uact=8&ved=2ahUKEwjugZTS5vXoAhXFyIUKH
XDrBdcQjRx6BAgBEAQ&url=https%3A%2F%2Fcedar.wwu.edu%2Fcgi%2Fviewcontent.cgi%3Farticle%3D1051%26context%3Dbiolo
gy_facpubs&psig=AOvVaw2QpCN-F2LmySjiUbj4o-8O&ust=1587430782958392
• The diagram shows the lactase gene and the preceding enhancer gene which is labelled as the
pre – gene area. The enhancer region shows the double stranded DNA which goes through
transcription process.
• This mutated gene has an allele which having a substitution which is shown by the circled
nucleotide (G). This mutated enhancer gene hence therefore, cannot act on the lactase gene to
stop or turn it off.

Cont’
• The enhancer region of the lactase region when then translated
after transcription, will eventually lead to formation of a
different protein which is not capable to turn the lactase gene
off.
• Due to the occurrence of this mutation in the nucleotides shown
above, the enhancer region stops working properly and hence
the body never stops to produce lactase.
• The description through which the protein synthesis is altered is
shown clearly by the processes involved in the transcription and
translation in the diagram above. This is essentially after the
mutation of the enhancer region (Farmer 37).

Pathway of the mutant and normal protein product with
their involved physical effects
https://www.google.com/url?sa=i&url=http%3A%2F%2Fwww.evo-ed.org%2FPages%2FLactase%2Fgenetics.html&psig=AOv
Vaw2vLJJXyBzZgoDSnWKKKz-d&ust=1587431314826000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNCW1tDo9egCFQ
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• The first part of the diagram shows the normal transcription and translation of the lactase gene
when there is no mutation in the enhancer region of the lactase gene. Since there is no mutation in
the enhancer region, there is no binding of the activator protein Oct1 which then leads to no
attraction of the general transcription factors. It indicates that after weaning, the transcription factor
activity is reduced at the lactase gene. This effect leads to a decreased transcription of lactase gene.

Cont’
•It then results into the lowering of lactase levels
present in the enterocytes rendering the
individual to be unable to digest the lactose
which is present in milk. The second part of the
diagram shows the mutated gene pathway
which is also called lactase persistence. It is the
pathway which involves the present of the
mutant gene leading to the binding of Oct1.

Cont’
• This pathway begins by a mutation in the enhancer region or the
pre-gene region at 13190 base pairs of the upstream portion of
the lactase gene. This then increases the process of Oct1, an
activator to bind. Binding of Oct1 leads to the attraction of
transcription factors to the lactase gene all through the life of an
individual up to the adult stage. It therefore, increases the
process of lactase gene transcription which would normally not
happen.
• The final result of this is the stead synthesis of lactase enzyme
in the enterocytes, enabling an individual to steadily retain
his/her ability to make lactose digestion happen in milk
throughout adulthood (Lahtvee 497).

Effects of lactase gene mutation at cellular level
• At cellular level, lactase gene mutation causes an increased binding of
Oct1 which is an activator, this then attracts transcription factors to the
lactase gene.
• This process occurs inside the cell of a person throughout adulthood. It
then prevents the normal process in the cell where transcription of lactase
gene is reduced therefore, increasing the transcription process of the
particular lactase gene (Wanes 461).
Effects of lactase gene mutation at tissue or organ level
• The effects of lactase gene mutation at organ or tissue level can be
described by the presence of a steady level of enterocyte’s lactase enzyme.
• This can therefore, enhance effective and retained digestion of milk both in
the stomach and small intestine throughout adult stages (Zhang 152).

Effects of lactase gene mutation at organism level.
• Mutation of the enhancer region of the lactase gene mainly affect the
whole organism in a positive way since an adult organism can still
consume milk since the increased number of lactase enzyme produced
can easily digest milk consumed by breaking down lactose (Viljoen 10).
How inheritance and expression of the mutated gene happens
• Lactose persistence involves a dominant allele mutation in the enhancer
region of the lactase gene. This follows explanations explained by the
Mendelian Inheritance with the perspective of complete dominance.
• For this particular condition to be inherited from the parents to the
offspring, one of the parents must have a single dominant allele for
lactose tolerance. The expression of LCT gene is controlled by the
sequences of DNA which are called regulatory protein elements and
located near MCM 6 gene (Futuyma 117).

How lactose persistence affects life expectancy and
whether it can be treated
•No treatment is required when talking about lactose
persistence effects. This is because this condition enables
one to break down lactose throughout life hence beneficial.
•Lactose persistence is beneficial and therefore, it improves
life expectancy through evolutionary advantages. Due to
the beneficial actions of this condition, there are additional
calories which are obtained from lactose persistence in
sporadic famines which is believed to aid in survival and
reproduction tremendously (Sokolova 14).

Works Cited
• Leseva, Milena N., et al. "Differences in DNA methylation and functional expression in lactase persistent and non-
persistent individuals." Scientific reports 8.1 (2018): 1-14.
• Ségurel, Laure, and Céline Bon. "On the evolution of lactase persistence in humans." Annual review of
genomics and human genetics 18 (2017): 297-319.
• Farmer, Tylar Seiya, Patrick Bohse, and Dianne Kerr. "Rational Design Protein Engineering Through
Crowdsourcing." Journal of Student Research 6.2 (2017): 31-38.
• Lahtvee, Petri-Jaan, et al. "Absolute quantification of protein and mRNA abundances demonstrate variability in
gene-specific translation efficiency in yeast." Cell systems 4.5 (2017): 495-504.
• Wanes, Dalanda, Diab M. Husein, and Hassan Y. Naim. "Congenital Lactase Deficiency: Mutations, Functional
and Biochemical Implications, and Future Perspectives." Nutrients 11.2 (2019): 461.
• Zhang, Jian, et al. "The impact of the intestinal microbiome on bone health." Intractable & rare diseases
research 7.3 (2018): 148-155.
• Viljoen, Johan W., et al. "Establishment and equilibrium levels of deleterious mutations in large populations."
Scientific reports 9.1 (2019): 1-10.
• Futuyma, Douglas. "Extended Heredity: A New Understanding of Inheritance and Evolution." (2019): 115-118.
• Sokolova, Inna M., et al. "Energy homeostasis as an integrative tool for assessing limits of
environmental stress tolerance in aquatic invertebrates." Marine environmental research 79
(2012): 1-15.