Module 3.7: Genes and Genetic Diseases

Genetics

the study of inheritance and differences of inherited genetics

Transcription

the transfer of genetic information from DNA to mRNA, carried out by RNA polymerase in 3 steps: initiation, elongation, and termination

Initiation

RNA polymerase binds to promoter, DNA starts to unwind

Elongation

RNA polymerase moves along template strand, building mRNA strand which is the complement to the DNA strand

Termination

RNA polymerase encounters a stop sequence in the gene and releases new pre-mRNA, ensures proper gene regulation

Splicing

process where non-coding sections of pre-mRNA are removed and remaining coding sections are joined together

Translation

when the genetic information encoded in mature-mRNA is translated, eventually leading to the construction of a functional protein, 3 stages: initiation, elongation, termination

Chromosomes

thread-like structures within cells of living organisms that carry genetic information in the form of DNA

Types: autosomes, sex chromosomes

Somatic cells

any cell in the body not involved in sexual reproduction

Gametes

reproductive cells, mutations will be passed on

Autosomes

first 22 pairs of human chromosomes, contain most of the body’s genetic information

Sex chromosomes

the 23rd pair of chromosomes, determine biological sex(XX=female, XY=male)

Types of genetic variants

point mutations, frameshift mutation, chromosomal mutation

Point mutations

silent mutation,, missense mutation, nonsense mutation

Frameshift mutation

insertions, deletions

Chromosomal mutation

deletions, duplications, inversions, translocations

Locations of genetic variants

somatic mutations, germ-line mutations

Pathologic gene variants

permanent changes to DNA sequence

types: monogenic, multifactorial/polygenic, germline, somatic

Monogenic gene variant

defect or alteration in one specific gene, inheritance pattern

Ex: cystic fibrosis, sickle cell, Huntingtons disease, Duchenne Muscular Dystrophy

Cystic Fibrosis

a disorder affecting the lungs and digestive system due to a mutation in the CFTR gene

Sickle cell

a blood disorder where red blood cells have an abnormal shape

Huntington’s Disease

a progressive brain disorder that results from mutations in the HTT gene

Duchenne Muscular Dystrophy

a genetic disorder that causes progressive muscle degeneration

Multifactorial/polygenic gene variant

multiple genes and environmental factors; congenital malformations, common diseases(heart disease, DM, cancer)

Germline gene variant

inherited and present at birth

Somatic gene variant

acquired with aging

Karyotype

a visual representation of an individuals chromosomes, sorted by size and arranged in homologous pairs

Normal karyotype

no structural abnormalities, 46 chromosomes

Abnormal karyotype

contain extra or missing chromosomes or structural changes, deletions or translocations

Euploid cell

correct number of chromosomes in complete sets

Aneuploid cell

wrong number of chromosomes, extra or missing individual chromosomes; can be a trisomy, monosomy, or polyploidy

Trisomy aneuploid cell

three copies of specific chromosome, extra chromosome, 3 instead of 2

Monosomy aneuploid cell

one copy of specific chromosome, lacking a chromosome, 1 instead of 2

Polyploidy aneuploid cell

more than the normal number of chromosome sets

Numerical chromosomal abnormalities

too many or too few chromosomes, Trisomy 21 or Turner’s Syndrome

Structural chromosomal abnormalities

changes to the structure of chromosomes; deletions, duplications, inversions, translocations

Causes of chromosomal abnormalities

errors during cell division, inherited mutations, environmental factors