GENETICS AND ITS APPLICATIONS


GENE: fragment of DNA which can be expressed to
synthesize important biomolecules,
eg. RNA (pretein synthesis)

->GENOME: collection of all genes in an individual
->Genes are present in chromosomes
->Chromosomes are in DNA
-->no. of chromosomes= 46
--->44= autosomes in 22 pairs
--->2= sex chromosomes 1 pair
->DNA is the genetic material= heritable material
->RNA is the genetic material with some viruses, eg. with HIV

MANDEL'S LAW OF INHERITENCE
->ALLELES
-->pair of genes occupying the same physical position of the paired chromosomes
-->alleles show the same character
->1st law: (segregation)
-->transmission of characters from parents to pffsprings occur evenly
->2nd law: (independent assortment)
-->distribution of 1 character to offsprings does not affect distribution of other characters
->GAMETIC DISEASES:
-->REASONS
--->abnormalities in chromosomal number
--->abnormalities in chromosomal character depends on abnormalities in the synthesis of certain protein
--->if 1 member of the pair is abnormal the normal gene would carry out other functions or the functions might be abnormal
--->in case of normal function normal gene is dominating & defect the recessive
--->in case of abnormal function defect is dominant

A=normal gene
a=abnormal gene
AA=normal function
Aa=normal function if 'a' is recessive
aa=abnormalities
aA=abnormalities if 'a' is dominant

->genetic make up: (dominants, recessives etc.)
-->called genotypes
->physiological status: whether the function is sick or not

aa, AA = homozygous
aA, Aa = heterozygous

->autosomal dominant disorders
-->AA=healthy
-->aA,Aa=diseased
->if father carries abnormal gene
-->50% of the children would have defective gene, no distinction of sex
-->expression of dieseases on mid 30s of age

->HUNTINGTON CHOREA:
-->dryness of nerve
-->death within 1-2 years
->NEVROFIBROMATOSIS:
-->cancer in brain
->AUTOSOMAL RECESSIVE:
-->AA=normal, Aa=carrier of defctive gene but normal, aa=dieseased

->GRANDFATHER CARRIER:
-->cousins likely to be carrier
-->25% chance of giving birth to diseased offsprings

GENETIC DIESEASES

SEXLINKED DIESEASES:
->X or Y chromosome linked dieseases
->if complication in X chromosome then X linked diesease

X linked dominant disorder: X=normal, x=defective

XX XY=normal
Xx xY=diseased

->if father is diseased daughters are dieseased
-->beacause:father can donate X chromosomes only to daughter
->if mother is dieseased both offsprings are dieseased
->eg: vitamin D resistant ricket

X linked recessive disorder:

XX=normal
Xx=carrier
xx=dieseased
xX=carrier but healthy
xY=dieseased

HEMOPHILIA:
->defective blood clotting due to absence of specific protein
COLOR BLINDNESS:
->X linked recessive disorder
GENETIC DEFECT:
->abnormal protein synthesis
->abnormal metabolism
->due to metabolic disorder

->if the protein is not an enzyme-->problem in other biological function
->if it is the B(beta) chain hemoglobin-->sickle cell anemia
->RBC with defective Hb-->sickle shaped RBC

->the sickle shaped RBC is destroyed by the body
->this causes anemia

->45XY
-->extra chromosome number is 2
->this is called DOWN SYNDROME
->chance of having babies with down syndrome increases with mothers age
-->10,000:1 if mother's age =below 20
-->7,000:1 if mother's age =below 30
-->350:1 if mother's age = more than or eual 35
->babies will have moon shaped face if they have down syndrome
->will also have flat nose, long tongue
->the child will be intellectually compromised

Extra X chromosome is made:
->XXY-->KLENIFFER SYNDROME
->male with certain secondary female character

->most of them will be infertile: 44XXY=47 chromosomes

TURNUR SYNDROME:
->XO
->one X missing in females --> 44X0 -->46
->female with less or without secondary sex character

HOW TO FIND OUT GENETIC DISORDER?:
->Diagnosis before birth/pre natal diagnosis by 1st trimester
->detection via:
-->CVS (chorinic villus sampling)
-->some fluid (with foetal cells floating) is collected from amniotic fluid
-->collected-->grown-->analyze for genetic defect
-->result by 12 weeks to 14 weeks
->CVS has to be done during 8-9 weeks of pregnancy

TREATMENT:
->lessen the complication in some cases
->galactosemia-->new born babiesfailing to utilize mother's milk
->give the child lactose free milk (therapetic baby food)
->gene therapy for defective gene

WHEN EXPRESSED ACTS AS A GENE: