What is a lactase gene?
The LCT gene provides instructions for making an enzyme called lactase. This enzyme helps to digest lactose, a sugar found in milk and other dairy products. Lactase is produced by cells that line the walls of the small intestine.
What is the genetic basis of lactase activity?
In humans, the ability to digest milk lactose is conferred by a β-galactosidase enzyme called lactase-phlorizin hydrolase (LPH) [2,3]. The LPH enzyme is encoded by the lactase (LCT) gene, located on the chromosome 2q21.
What is the lactase persistence gene?
The lactase persistent phenotype involves high mRNA expression, high lactase activity, and thus the ability to digest lactose, while the lactase nonpersistent phenotype involves low mRNA expression and low lactase activity. The enzyme lactase is encoded by the gene LCT.
Where is the lactase gene located?
Lactose intolerance in adulthood is caused by gradually decreasing activity (expression) of the LCT gene after infancy, which occurs in most humans. The LCT gene is found on chromosome 2 (https://medlineplus.gov/genetics/chromosom e/2/).
How is the lactase gene turned off?
These studies imply that after early childhood, the lactase gene is usually shut off by DNA methylation. The SNPs that alter the DNA sequence in the control region, however, prevent this methylation from happening. This, in turn, results in the production of lactase because the gene is kept on.
Is lactase a mutation?
Some humans, however, continue to produce lactase throughout adulthood, a trait known as lactase persistence. In European populations, a single mutation (−13910*T) explains the distribution of the phenotype, whereas several mutations are associated with it in Africa and the Middle East.
Where did the gene for lactose intolerance come from?
People who can digest lactose often originate from northwest Europe (like many New Zealanders) and some parts of Africa. The genetic mutation that allows them to do this arose relatively recently, about 12,000–10,000 years ago, as farming became a major source of food.
Is lactase persistence dominant or recessive?
autosomal-dominant trait
Lactase persistence is an autosomal-dominant trait that is common in European-derived populations.
What is the difference between lactose tolerance and lactose persistence?
Lactose intolerance is the result of being homozygous for the recessive lactase allele that is poorly expressed after early childhood. Being homozygous or heterozygous for the persistence allele allows lactase expression after the time when lactase expression is normally down-regulated.
What produces lactase in the body?
The small intestine produces lactase, an enzyme that breaks down lactose. The small intestine is an organ that breaks down the food you eat.
How is the lactase gene regulated in humans?
It is accepted that lactase gene expression is primarily regulated at the transcriptional level33,34,35, and in non-human mammals Cdx2, Gata4/6 and Hnf1α TFs collectively activate this gene.
Is being lactose intolerant normal gene?
As you can guess from the numbers, being lactose intolerant is normal for an adult. People who can drink milk as an adult have a DNA mutation. In fact, being able to drink milk as an adult is now referred to as a condition called lactase persistence.
What is the main function of lactase?
lactase, also called lactase-phlorizin hydrolase, enzyme found in the small intestine of mammals that catalyzes the breakdown of lactose (milk sugar) into the simple sugars glucose and galactose.
What are the 4 types of lactose intolerance?
Types of lactose intolerance
- Primary lactose intolerance (normal result of aging) This is the most common type of lactose intolerance.
- Secondary lactose intolerance (due to illness or injury)
- Congenital or developmental lactose intolerance (being born with the condition)
- Developmental lactose intolerance.
Is lactose intolerance a dominant gene?
Lactose intolerance is a recessive trait, whereas lactase persistence is dominant.
Is the lactose tolerance gene dominant?
Lactose tolerance is traditionally thought of as an autosomal-dominant genetic trait, although the actual levels of lactase in the intestinal mucosa show a trimodal distribution, with very low levels in the people homozygous for the lactase non-persistence variant.
What type of mutation is lactose tolerance?
A single point mutation in the DNA near to the lactase gene changes the cytosine (C) nucleotide to a thymine (T). Individuals who have the thymine (T) nucleotide are lactose tolerant and can digest milk products in adulthood.
Why is lactase important?
Lactase is the enzyme responsible for the digestion of the milk sugar lactose and its production decreases after the weaning phase in most mammals, including most humans.
What causes lactase deficiency?
Primary lactase deficiency is the most common cause of lactose intolerance worldwide. This type of lactase deficiency is caused by an inherited genetic fault that runs in families. Primary lactase deficiency develops when your lactase production decreases as your diet becomes less reliant on milk and dairy products.
Which term best describes lactase?
Which term best describes lactase. Enzyme. Descirbe Enzymes.
Is lactose intolerance a normal gene?
Lactose Intolerance and Genes
As you can guess from the numbers, being lactose intolerant is normal for an adult. People who can drink milk as an adult have a DNA mutation. In fact, being able to drink milk as an adult is now referred to as a condition called lactase persistence.
What are the 4 types of lactase deficiency?
Lactase deficiency exists in four distinct forms: primary (the most common), secondary, congenital, and developmental. Treatment of primary lactase deficieny is indicated only when it manifests as a clinical syndrome of lactose intolerance. Dietary elimination and challenge are generally diagnostic.
What is lactase deficiency called?
People with lactose intolerance are unable to fully digest the sugar (lactose) in milk. As a result, they have diarrhea, gas and bloating after eating or drinking dairy products. The condition, which is also called lactose malabsorption, is usually harmless, but its symptoms can be uncomfortable.
What are the 5 parts of an amino acid?
All amino acids include five basic parts:
- a central carbon atom.
- a hydrogen atom.
- an amino group – consisting of a nitrogen atom and two hydrogen atoms.
- a carboxyl group – consisting of a carbon atom, two oxygen atoms, and one hydrogen atom.
- an R-group or side chain – consisting of varying atoms.
Which of the following may occur if the body is unable to produce the enzyme lactase quizlet?
Which of the following may occur if the body is unable to produce the enzyme lactase? The colon may swell due to an excess of gas and fluid.