The role of genes as a determinant of lifetime health Flashcards
What is nutrigenomics?
Study of how diet influences gene expression (on/off)
* some genes are more sensitive to certain nutrients
* Change in phenotype without a change in genotype
What is nutrigenetics?
Study of how genetic differences arising from polymorphisms modifies dietary effects
What are the nucleotide bases?
- adenine
- thymine
- guanine
- cysteine
What is the central dogma of biology?
What is the difference between phenotype and genotype?
- Genotype is a persons unique sequence of DNA. More specifically, this term is used to refer to the two alleles a person has inherited for a particular gene
- Phenotype is the detectable expression of this genotype – a patient’s clinical presentation
Genotype: aabb Phenotype: green, wrinkled
What is a polymorphism?
refers to the presence of two or more variant forms of a specific DNA sequence that can occur among different individuals or populations.
What is the most common type of polymorphism?
SNP - single nucleotide polymorphism
* involves variation at a single nucleotide whereby the replaced nucleotide may or may not produce a change in the phenotype
What are common examples of SNPs?
- sickle cell disease - HemoglobinS allele
- SREBP-1c
- Apolipoprotein E4
- Myostatin
- PWS
What is the SNP in sickle cell disease?
Autosomal recessive HbS+HbS; A nucleotide in the DNA sequence is flipped in the HgbS allele which expresses the protein valine instead of glutamic acid in the AA sequence resulting in malformation of RBCs such that it might not be functional inhibiting ability to carry oxygen
■ AA – homozygous for the ‘normal’ Hb allele
❑ disc-shaped RBCs
■ AT – heterozygous for the Hb/HbS alleles
❑ some disc-shaped and some with potential to sickle (no clinical symptoms)
■ TT – homozygous for HbS allele
❑ RBCs that can sickle (sickle cell disease)
What is the result of a SNP in the SREBP-1c?
changes in response to diet since this protein regulates lipid metabolism
* Snp present + high fat diet consumption leads to overexpression which is associated with dyslipidemia, impaired glucose metabolism, Type-2 diabetes
What is the result of a SNP in the apolipoprotein E4
Apo E4 egulates lipoprotein-cholesterol clearance from plasma so a SNP causes changes in response to diet
* ApoE4 allele + high fat diet results in higher LDL levels, cardiovascular outcomes and alzheimers disease
What is the result of a SNP in myostatin?
myostatin is a hormone that inhibits muscle protein synthesis so a SNP causes changes to body composition
Whippets (racing dogs) having MSTN gene variant mh (deletion)
▪ +/+ normal muscle and speed
▪ +/mh more muscle and faster speed
▪ mh/mh bulky muscle and slower
What is PWS?
prader-willi syndrome: chromosomal deletion with multiple genes affected
* hypothalamic dysfunction: growth hormone, hunger-satiety hormones, other endocrine
* short stature, lower lean mass, hyperphagia (lack of satiety), developmental delays
* failure-to-thrive in infancy
* food seeking in early childhood
What is epigenetics?
Changes in gene expression (phenotype) caused by mechanisms other than changes in the underlying DNA
What are the mechanisms by which epigenetics may induce a change?
non-genetic factors cause the organism’s genes to be expressed differently such as the environment in the organisms exists
* allows for adaptations to environment
* changes remain through cell divisio