2. Genetics and environment

deoxyribose nucleic acid

individual coding molecules, carries the genetic info for development

A:T -> adenine / thymine

G:C -> Guanine / cytosine

hydrogen bonds form between them

organized bundle of DNA

23 pairs

proteins that support DNA

protein-specific DNA sequence code -> instructions for making proteins

DNA is a recipe book for our cells to produce different types of proteins

Each cell has the same recipe book, but each cell will not make the same recipe

genes go through transcription in the nucleus, they travel with mRNA to cytoplasm where the translation happens to become protein

the process of making an RNA copy of a gene's DNA sequence, called mRNA

the decoding of instructions for making proteins

when cells divide, they both need a copy of DNA

DNA helicase = template unzipping, they unwind the DNA

DNA polymerase = nucleotide addition + proofreading, they assemble it

DNA ligase = seals off new DNA

any form of error in sequence

genes with mutation frequency > normal -> genetic disorders

substances that increase mutation rate (radiation, alkylating agents -> chemo)

missense mutation -> a DNA change that results in different amino acids being encoded at a particular position in the resulting protein -> switch pairings (ex: AT for GC)

nonsense mutation -> a change in DNA that causes a protein to terminate or end its translation earlier than expected -> codes for stop codon

frameshift mutation -> a genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read -> everything is ruined

sex

XX: female

XY: male

yes, but not all is used in every cell

a process of cell duplication, or reproduction, during which one cell gives rise to two genetically identical daughter cells

1) Prophase n=4Chromatin into chromosomes, the nuclear envelope break down, chromosomes attach to spindle fibres by their centromeres.2) MetaphaseChromosomes line up along the metaphase plate (centre of the cell).3) AnaphaseSister chromatids are pulled to opposite poles of the cell.4) Telophase n =2Nuclear envelope reforms, 2 new identical cells

a type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes

like mitosis but happens 2 times -> 2 divisions

end result is 4 daughter cells that are not identical

during division the structure of the chromosome is affected

polyploidy and aneuploidy

error in meiosis

multiple of 23 chromosomes

ex: 3 copies instead of 1

not a multiple of 23 chromosomes

ex: trisomy 21 = 47 chromosomes (1 extra chromosomes in pair 21)

a stillborn baby -> there is too much info for it to survive

Down syndrome is rare type that is still viable

we only need one X chromosome to live

Y chromosome is so small, barely any info

loss of paternal X chromosome

characteristics: short, abnormal female genitals, exogenous estrogen for secondary sexual development

extra X chromosome

characteristics: male appearance + sterile, small testes and female breast development, increased physical + mental alterations

deletion

duplicate

inversion

reciprocal translocation

it gets deleted -> loss of info

ex: cri du chat syndrome

gets duplicated -> too much info

ex: Huntington's disease

2 of them switch spots, no loss no problems BUT -> if swap breaks gene it is a problem

sections swap from different pairs -> can lead to problems but not always

ex: chronic myeloid leukemia (CML), chromosome 9 and 22 switch sections which leads to increased cell division in blood cells

outward appearance of organism, expression of trait

ex: blue or green eyes

maternal + paternal alleles pair

ex: B - blue eyes. b - green eyes

3 possibles genotypes: BB (homozygous), Bb (heterozygous), bb

ONLY concerned with pairings of alleles

variants of gene

ex: gene -> eye color, allele -> green

2+ alleles w/significant frequency in population

dominant is always expressed: FF and Ff

recessive only if it is ff, not Ff

a form of Gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype

ex: red + white flower make a pink flower

phenomenon in which two alleles are expressed to an equal degree within an organism

ex: red + white flower make red/white striped flower

AB blood type

used to map out genotypes + phenotypes

an abnormal gene from one parent can cause disease.

2 affected parents -> 66% chance

1 affected parent -> 50% chance

ex: Huntington's disease, achondroplasia

both genes in a pair must be abnormal to cause disease

around 25% risk

parents are usually healthy carriers

IF there is incest, risk increases to 66%

healthy dad x carrier mom

carrier dad x healthy mom

2 carrier parents (only scenario where female can be affected)

if an X copy is bad, the other one will take over in female

male only has one X copy

inheritance: # of new cases in timeframe within population -> no info on genetics

prevalence: ratio of affected individuals at specific time -> yields info on genetics

identical: 1 sperm + 1 egg

fraternal: 2 sperm + 2 eggs (no more similar than siblings)

1. MZ 95%, 49% -> fingerprints are genetic based

2. MZ 95%, 87% -> measles are environment based

3. MZ 47%, 12% -> genetics have a bigger role, but environment has too

4. MZ 76%, 51% -> IQ is both genetics n environment

a characteristic, such as height or skin color, that is influenced by two or more genes

how your behaviors and environment can cause changes that affect the way your genes work

doesn't change what is written in ur gene -> but how fast its reading and what chapters

modifies expression pattern of some genes

influenced by environmental factors

some epigenetic modifications can be transmitted to offspring

only one copy of a gene in an individual is expressed, while the other copy is suppressed

imprinted -> inactive, no protein can go read there

environmental protection: dehydration (keratinization), UV (melanin), pathogens (langerhans cells), mechanical stress (Merkel cells)

top to bottom: stratum corneum, stratum granulosum, stratum spinosum, stratum basale

it take around 30 days for dead cell to go from stratum basale up to surface to be shed

hair shaft, nerves, sweat + sebaceous glands, lymphatic + blood vessels, mast cells (immune)/macrophages/fibroblasts (produce collagen)

adipose tissue + blood vessels

connects skin to muscles

secrete sebum that prevents drying

protective keratinized (dead cells) plates

eccrine: thermoregulation

apocrine (bad smell): armpits + genitals -> unknown function

small blood vessels at surface of skin

body temp regulation

form unit w/sebaceous gland + erector pili muscle (contract if ur cold to keep u warm)

male-pattern -> gradually replaced by vellum (sparse light hair)

top of head follicles = androgen sensitive

back + sides follicles = androgen insensitive

female-pattern -> progressive thinning + loss

alopecia areata -> T-cell mediated autoimmune, chronic inflammation of follicles

male pattern hair growth in women -> evaluate for endocrine disorders

infection of cuticle, strepto or staphylococcus bacteria

moisture increases risk

painful + abscess may form

infection of nail plate, hyperkeratotic debris within plate

yellow + elevated nail, fungal infection

1: superficial freezing

2: full thickness freezing

3: deep: full thickness + subcutaneous freezing

4. deep: full thickness + subcutaneous freezing + gangrene (cells undergoing necrosis)

decrease of melanocytes + langerhan cells

decrease in elastin, collagen and fibroblast

wrinkles is also environmental damage (UV, smoking, nutrition...)

decreased touch + pressure receptors

decreased vasculature + immune cells

constant pressure occluding blood vessels -> ischemia -> increased cells necrosis

prolonged immobilization, impaired perfusion, shearing forces

allergen contact on skin -> triggers immune cells -> T-cell activation + cytokine release -> inflammation

itching/swelling + erythema

time for t-cell activation + inflammatory mediators effects

a T-cell/delayed type-IV hypersensitivity reaction

immune response to harmless molecules

inflammation response to an actual injury

skin barrier compromised -> exposition to irritant -> inflammation in response to injury

injury proportional to irritant concentration + exposure

helper t-cell mediated autoimmune disorder

PSORS1 gene = genetic susceptibility

Th17/IL-23 pathway hyperactivation -> extensive/constant skin inflammation -> keratinocyte hyperplasia + increased vasculature -> plaque formation

any of 4 risk factors: hyperkeratinization, increase sebum production(increase in androgen and testosterone levels), increase proliferation of P. acnes bacteria, rupture of sebaceous follicle -> skin pore obstruction -> inflammation

possibly immune-mediated, not well understood, not associated w/ P acnes bacteria or testosterone

chronic abnormal vasodilation -> erythema

systemic lupus w/cutaneous only manifestations

has genetic susceptibility : increased self reactive T & B cells, decreased regulatory T cells

has photosensitivity: lesions located on light exposed regions (butterfly face lesion)

can progress into SLE

UV light + altered immunity -> activation of self-reactive T & B cells -> formation of autoantibodies immune complexes (AIC) -> skin damage + vasculitis

HSV-1 (cold sores) + HSV-2 (genital herpes) -> lesions = rash + inflamed vesicles

virus infects epithelium cells -> latency in dorsal root ganglion (hides in neurons, often in CN V) -> viral reactivation -> skin lesions

80% of population has this, easy transmission, very little have lesions, so hard to get rid of because it is always "hiding"

varicella-zoster virus (VSZ; HSV-3) -> lesions = shingles or infected dermatome

virus infects epithelium cells -> latency in dorsal root ganglion -> viral reactivation -> skin lesions

immunocompromised are at higher risk, SUPER painful

vascular-malignancy associated w/immunosuppresion (ex: organ transplant, AIDS, HIV)

immunosuppression -> latent HSV-8 opportunistic infection -> multifocal lesions + inflammation at blood vessels -> characteristic purple plaques + nodular lesions

classic: slow progression, affects lower extremities

AIDS: rapid progression, affects upper body, face, visceral organs

multisystem bacterial infection by borrelia burgdoferi -> transmitted by tick bites

tick bite -> bacterial invasion of tissues -> localized erythema migrans (T-cell mediated) -> systemic spreading -> secondary erythema migrans + complications

1. localized erythema migrans - days after bite

2. spreading of illness w/neuralgias and neuritis/carditis -> weeks

3. late persistant -> can lead to encephalopathy + heart failure

ointements -> oil based, high absorption, dry/thick skin, bad oozing wounds

creams -> oil + water, dry inflamed skin, better for rubbing

lotions -> mostly water, alcohol/acids, good for large/hairy areas, decrease oiliness

powders -> cornstarch base, perspiring regions

pastes -> ointment + powder, occluded areas, powder increases skin adherence

foams -> shaving, quick dry no residues

gels -> cellulose/water or oil, oily skin, large/hairy areas, facials

anti-inflammatory + itching for many skin conditions

potency depends on concentration, formulation + area applied, absorption increased by occlusive dressing

local: increased infection risks + irritation

systemic: growth delay + adrenal suppression

occlusive dressings + large areas increase toxicity

thin films + gentle rub, avoid occlusive dressings unless told

they promote shedding of superficial skin layer, used to treat skin overgrowth or abnormal thickening

salicylic acid: dissolves surface intercellular connections -> 3-6% for acne +psoriasis, 6-40% for warts

topical sulfur: promotes peeling + drying, for acne/psoriasis/dandruff, combined w/salicylic acid

minoxidil: potent vasodilator, unknown mechanism -> delay hair loss + increase growth, hair loss resumes if discontinued

finasteride: inhibits DHT production which decreases hair shrinking -> modest hair growth, effective in 50%

decrease scarring, psychological burden + limit symptom duration

non-irritant soap (decrease oil), avoid vigorous scrubbing, avoid makeup/moisturizers, NOT DIET CHANGE

drugs!

mild: topical retinoids or antibiotics

moderate: antibiotics

severe: oral retinoids

decrease P.acnes growth + inflammation

benzoyl peroxide: no resistance development but risk of anaphylactic reaction

clindamycin/erythromycin: minimal toxicity but quick resistance development

doxycycline: less resistance development, 3-6 months for benefits

normalize epithelial cells hyper proliferation -> unplug + inhibit blackheads

thinning of stratus corneum -> increased topical Rx absorption

not better than good skin care + sunscreen

no systemic effects only localized, increased sunburn risk

decrease sebum/inflammation/keratinization

nose bleeds/lip inflammation/sunburns = common

erectile dysfunction/increased blood triglycerides/depression = less

DO NOT TAKE IF PREGGO - teratogenic

drug interactions: tetracyclines + vitamin A supplements

UVB (5% total earth radiations): epidermis only -> burning/tanning/cancer

UVA (95% total earth radiations): epidermis + dermis -> photoaging, photosensitive

sunburn, photosensitivity, photoaging, melanoma, squamous cell carcinoma

PABA + oxybenzone

when exposed to UV light, time to produce redness on protected skin/time to produce redness in unprotected skin

15+