BIO1100 Dr. Morris Troy University Exam 4 - Module 7 & 8, Basic Genetics

What is a gene? (2 defs)

• = “an inherited unit”

• = a specific order/sequence of nucleotides on DNA that codes for a certain protein

What (combo of things) determines the appearance of living things?

Proteins + environmental / behavioral factors

Central Idea for Molecular Genetics & Biotechnology

Replication (what, when happens)

= DNA synthesis — happens during “S” of Interphase

Transcription

= RNA synthesis

Translation

= Protein synthesis

Who is the “Father of Genetics”?

Gregor Mendel

Allele

= an alternative form of a gene; 1n = haploid (in gametes/sex cells)

Genotype

= the actual combination of alleles; 2n = diploid (body cells)

Phenotype

= physical appearances of individuals (**PHenotype, PHysical)

Dominant

= the allele that overrides (“masks”) the recessive if the 2 come together

Recessive

= the allele that gets overridden if the 2 come together

Heterozygous

= the alleles are NOT identical

Homozygous

= the alleles are identical

What is a hybrid? (2 defs, explain first )

• = a cross btwn 2 diff species / kinds of organisms

  • Ex. ligers, mules

  • Mostly can’t reproduce

  • Hybrid vigor

• = a cross btwn 2 (parent) individuals that were diff by ≥1 characteristic

What is a liger a cross between?

Lion + Tiger

What is a mule a cross between?

Donkey + Horse

Hybrid vigor

= when hybrids are more strong to endure changes than purebreds

(7) Common Human Characteristics that show Dominant-Recessive Inheritance

• Earlobes

• Freckles

• Tongue-rolling

• Mid-digital hair

• Hitchhiker’s thumb

• Double-jointedness

• Dwarfism

Earlobes (dominant vs. recessive)

• Dominant = UNattached / free (EE or Ee)

• Recessive = attached (ee)

Freckles (dominant vs. recessive)

• Dominant = having freckles (FF or Ff)

• Recessive = NOT having freckles (ff)

Tongue-rolling (dominant vs. recessive)

• Dominant = ability to roll (TT or Tt)

• Recessive = INability to roll

Mid-digital hair (dominant vs. recessive)

• Dominant = having hair (MM or Mm)

• Recessive = NOT having hair (mm)

Hitchhiker’s thumb (dominant vs. recessive)

• Dominant = NOT hyperextended (II or Ii)

• Recessive = hyperextended (ii)

Double-jointedness (dominant vs. recessive)

• Dominant = having it (DD or Dd)

• Recessive = NOT having it (dd)

Dwarfism (dominant vs. recessive)

• Dominant = having it (WW or Ww)

• Recessive = NOT having it (ww)

Which recessive trait is more common than its respective dominant trait?

Not having freckles

P generation (what, requirements for monohybrid cross)

= parental generation; in a monohybrid cross, 1 parent must be homozygous dominant, other must be homozygous recessive

F₁ generation

= 1st generation of offspring

F₂ generation

= 2nd generation of offspring

What is the “F” for in F₁ and F₂?

Comes from “Filial”, Greek for “son”

Punnet square (use)

Used to figure out Genotype & Phenotype ratios of the F₂ generation

Mendel’s 1st Law (aka, def, essentially what)

• aka Law of Segregation

• = “alleles separate/segregate during gamete formation”

• Essentially Meiosis (diploid → haploid)

In a Monohybrid Cross, 2 parents are crossed that differ by…

1 and only 1 trait

What is the predicted genotypic ratio for a monohybrid cross with 1 homozygous dominant parent and 1 homozygous recessive parent?

1:2:1

What is the predicted phenotypic ratio for a monohybrid cross with 1 homozygous dominant parent and 1 homozygous recessive parent?

3:1

Mendel’s 2nd Law (aka, def)

• aka Law of Independent Assortment

• = “characteristics or traits are inherited one-by-one/singly, but not necessarily as a set”

In a Dihybrid Cross, 2 parents are crossed that differ by…

2 and only 2 traits

What is the predicted phenotypic ratio for a dihybrid cross with 1 homozygous dominant parent and 1 homozygous recessive parent?

9:3:3:1

4 Major Categories of Human Genetic Conditions

1. Autosomal Dominant

2. Autosomal Recessive

3. X-Linked Recessive

4. Multi-Factorial

Autosomal Dominant (what, how passed on)

• = a change in any 2 of first 22 pairs of chromosomes, dominant allele affected

• Only 1 parent has to have condition

(4) Autosomal Dominant conditions:

“All Hunted-Deer Play Dead”

1. Alzheimer’s Disease

2. Huntington Disease

3. Polydactyly

4. Dwarfism (Achondroplasia)

Which 2 of these conditions are common and why?

Alzheimer’s and Huntington disease — show up post-reproduction

Alzheimer’s Disease (form, type, affects what, when it takes effect, what it leads to)

• 1 form that is purely genetic

• Neurodegenerative

• Affects memory — short-term goes first

• Usually takes effect around 30-60

• Leads to complications of other organ systems (brain controls them) and eventually death

Huntington Disease (type, when it takes effect. what it leads to)

• Neurodegenerative

• Can take effect 30s & 40s

• Leads to complications of other organ systems (brain controls them) and eventually death

Polydactyly (what it is, parents’ role in treatment)

• “Many digits”; extra fingers & toes

• Parents can either allow the child to decide to have them surgically removed, or decide for them

Dwarfism (aka, what w/measurement, Dd x Dd → what)

• Aka Achondroplasia

• Unusual shortness (4ft)

• Can lead to difficulties;

• Dd x Dd → 75% chance (homo/heterozygous) dominant, 25% chance (homozygous) recessive; 2 dwarves CAN have children of avg. height, IF both heterozygous dominant

(3) difficulties people with dwarfism face:

• Gastrointestinal issues

• Reproductive issues

  • 1st 2 because everything is compacted

• Day-to-day challenges

Which is more common in the general human pop.: autosomal recessive or autosomal dominant?

Autosomal recessive

(5) Autosomal Recessive conditions:

“All Crazy-Freaking Sickness TargetS Pre-K”

1. Albinism

2. Cystic Fibrosis

3. Sickle-Cell Disease

4. Tay-Sachs Disease

5. PKU

Albinism (what gene mutated, effects)

• Genetic condition in which there’s been a mutation in the gene that codes for melanin

• Effects:

  • More susceptible to getting sunburnt

  • Much higher chance of skin cancer

  • Improper vitamin D levels → problems w/skeletal & immune systems

Melanin

= pigment that absorbs sunlight & protects skin cells from harmful radiation of the sun (UV rays)

Cystic Fibrosis (what gene mutated, what happens in body, 3 effects)

• Gene that’s been mutated that codes for a protein in the cell membrane

• Protein is supposed to move chloride ions (Cl^-) → can’t cross membrane → excess buildup of mucus outside the cells

  • Mucus traps germs, but in cf, it just accumulates and the germs never leave the body

• Effects:

  • Very prone to respiratory infections — esp. pneumonia

  • Shortened lifespan (often die of pneumonia), up to 40s now

  • Other places w/mucus affected; digestive & reproductive systems

Sickle-Cell Disease (what gene mutated, origin)

• Gene is mutated that codes for hemoglobin → doesn’t carry O₂ as well

• Came about as an adaptation to resist malaria, likely a spontaneous mutation in ppl who live in warm, tropical conditions

Malaria (what, how spread)

• = characterized by a very high fever to level of brain damage

• Spread through a specific type of mosquitoes;

What type of mosquitoes spread malaria?

Anopheles; mosquitoes = vectors

Vectors

= anything that spreads disease

3 possible genotypes associated w/sickle-cell:

• SS (homozygous dominant)

• Ss (heterozygous dominant)

• ss (homozygous recessive)

People with SS… (rbc shape, effect of malaria)

• Do not have sickle cell

• Have regular red blood cells shaped like “bi-concave disc”

• Would die from malaria

People with Ss… (effect of malaria, symptoms of sickle cell?)

• Are carriers of sickle cell

• Are what nature wants people to be (heterozygous dominant)

• Very resistant to malaria, but showing few symptoms of sickle cell

  • ex. difficulty breathing in high altitudes

People with ss… (rbc shape, SA, effects)

• Have sickle cell

• Have red blood cells shaped like sickle

• Less SA than normal rbc → harder time transporting oxygen

• Effects:

  • Fatigue, could lead to coma and death if not treated

  • Needle-like pain in capillaries as pointy blood cells pass through and clog up small blood vessels

(3) Good treatments for sickle cell:

• Stem cells

• Gene therapy

• Chemotherapy

Stem cells

= young cells that can be trained to become any kind of cell

Gene therapy (what it does in general & in case of sickle cell)

• = correcting a problematic gene by injecting a virus particle that inserts its DNA into human DNA

  • Ex. chicken pox, virus inserts DNA into host → host may develop shingles later in life

• In case of sickle cell, take harmless virus and give it DNA to make hemoglobin, then give the human that virus so it will insert that good DNA into their DNA

Chemotherapy (what it does in general & in case of sickle cell)

• = used to kill bad cells

• In case of sickle cell, kills off bone marrow cells that make sickle-shaped red blood cells, allows for replacement with cells that make normal red blood cells

What is the brain largely comprised of?

Lipids

Tay-Sachs Disease (what gene mutated, what happens in body, effects, who more commonly found in)

• Due to a mutation in the gene present in lysosome that codes for a lipid-digesting enzyme → buildup of lipids in brain

• Leads to babies born w/brain damage, typically shortened lifespan up to toddler years

• More common in Eastern European, Amish (dutch), Jewish populations

PKU (what gene mutated, what happens in body, effects historically vs. now, testing, treatment)

• Aka Phenyl Ketonuria

• Due to a defective/mutated gene that codes for processing (breaking down) the amino acid phenylalanine

• Similar to Tay-Sachs — too much phenylalanine becomes toxic and can cause brain damage

• Historically, babies born seemed fine, gradually went back in cognitive abilities, death in toddler years

• Now, “newborn screening” (toe prick) can catch PKU

• Hospital will give parents resources for protein-rich recipes that exclude phenylalanine

• Can live a full life w/diet modification

Which is bigger, the X or Y chromosome?

X chromosome

X-Linked Recessive (what, how passed on female vs. male)

• X chromosome → larger SA → chance of condition on it goes up

• In males, just have to be heterozygous → much more common in males

  • Typically passed on from mother (carrier) to son

• In females, must be homozygous

(4) X-Linked Recessive conditions:

“Red-and-Green Happen Doubly-Much For-Xmas”

1. Red-green colorblindness

2. Hemophilia

3. Duchenne Muscular Dystrophy

4. Fragile X Syndrome

Red-green colorblindness (what gene mutated, effects)

• Mutated gene that codes for light receptor proteins found in retina of the eye

• Only see a fraction of the range of colors the avg. person sees

• Can’t see red against a green background

• Range of affectedness

Hemophilia (aka, effects, what gene mutated)

• Aka “bleeding to death disease” — can’t blood clot, even small cuts and bruises can be deadly, internal and external

• Due to a defective/mutated gene that codes for blood-clotting factor (proteins) in a chain reaction

• Has a history;

• 2 good treatments;

History of hemophilia: (aka, family line, now even found in what)

• Dubbed the “royal disease” — 1st discovered in royal families

• Spontaneous mutation in 1 of Queen Victoria’s parents

• → Queen Victoria = carrier

• → her daughters = carriers

  • married to royal family in Spain and Russia

• → their sons (princes) = had hemophilia

• Has also been discovered in cats & dogs

2 good treatments for hemophilia: (+ which is more expensive)

• Regular injections of the proper blood-clotting factor

• Take a pill that has the proper blood-clotting factor

  • Much more expensive

Duchenne Muscular Dystrophy (what gene mutated, what happens, effects, treatment?)

• Due to a defective gene that’s supposed to code for the protein dystrophin

• Atrophy (wasting away) of muscle tissue

  • All kinds of muscle tissue — smooth, epithelial, cardiac

• When learning how to walk, will have a “characteristic rising position” (L-shaped, bent over)

• Wheelchair bound by late elementary grades

• Death in their 20s

• They tried gene therapy, but it didn’t work because the gene that codes for dystrophin is really big and it fell apart when they tried to move it

Fragile X Syndrome (due to what, what, percentage, effects)

• Due to ≥1 weak pt. on X-chromosome

• = a purely genetic form of autism

• No more than 20% of autism, even tho historically was main cause

• Ppl can be completely nonverbal, but often have 1 really special talent, esp. math

Multi-Factorial (due to what)

De to a combination of genetic predisposition + environmental/behavioral factors

(5) Multi-Factorial conditions:

“My-Cousin-Has All DeLoreans Parked Around”

1. Many forms of cancer & heart disease

2. Many forms of Alzheimer’s disease

3. Type 2 diabetes

4. Parkinson’s disease

5. Many forms of autism

Many forms of cancer & heart disease (prevention)

Prevent through healthy exercise & diet, regular checks

Many forms of Alzheimer’s disease (potential causes observed)

• Aluminum found in brain autopsies, potential correlation

• Misfolded proteins also found in brain, interfere w/brain signals

Type 2 diabetes (prevention, what, effects- organ systems)

• Prevent by lowering carb intake, exercise, regular checkups for blood sugar levels

• Affects insulin (controls blood sugar levels)

• Eventually can affect multiple organ systems

  • Nervous system — high blood sugar → brain damage → can lead to dementia

  • Cardiovascular system — elevated b.p. → heart disease

  • Potentially cancer involved

Parkinson’s disease (what, effects, treatments)

• Neuromuscular disease affection neuromuscular junctions (communication btwn nervous system & muscles)

• Uncontrollable tremors

• Especially affecting dopamine — drugs taken to help are targeted at correcting dopamine levels

• In certain studies, regular exercise on stationary bicycles dramatically reduced tremors

Many forms of autism (percent, what, causes, genes?, treatment)

• The other 80%

• Uneven development — above avg. development but lacking social abilities

• Exposure to certain environmental toxins;

• They’ve discovered multiple genes involved w/coding for autism

• Gluten-free (wheat), casein-free (dairy products) diet found effective

2 toxins associated w/multi-factorial autism: (where found)

• Arsenic

  • In pesticides

• Mercury

  • Burning fossil fuels

  • Living in area w/history of gold mining

  • Eating fish high on food chain;

(4) Fish high in mercury:

• Tuna

• Swordfish

• Marlin

• Shark

(1) Fish intermediate in mercury:

Salmon

(4) Fish low in mercury:

• Flounder

• Codfish

• Sardines

• Mackerel

4(.5) Fetal Testing Procedures:

1. Ultrasound

2. Amniocentesis

3. Chorionic Villi Sampling

4. Fetoscopy

5. (Newborn Screening)

Ultrasound (procedure, risk factor, how often done)

• Subject fetus to very high-frequency sound waves that literally bounce off body of fetus and are picked up by special monitoring equipment to produce an image

• —result→ sonogram

• 0% risk factor to mother and baby

• Typically done twice during pregnancy;

What (2 things) can / (1 thing) can’t be determined by an ultrasound?

• Gender can be determined at 4.5 months, IF the baby cooperates

• Baby’s position determined before birth — make sure head-first (otherwise, breach birth puts pressure on baby’s head & can cause brain damage)

• Can’t determine chromosomes

What (3 things) can be seen on an ultrasound and what corresponding conditions can be checked for?

• Skeletal system — check for conditions like spina bifida

• All large blood vessels & heart — check for narrowing of aorta

• Fingers & toes — check for polydactyly

Amniocentesis (procedure, testing)

• Take ≈ a teaspoon worth of amniotic fluid to try and extract old skin cells of baby

• Culture/grow old skin cells in a lab, stop them @ metaphase and take a picture of them

• Karyogram/type OR biochemical tests can be done

  • Biochemical more for PKU, tay-sachs, etc.

(3) Drawbacks of Amniocentesis:

• 1% risk factor to mother and baby used, could poke baby BUT use ultrasound to see exactly where baby is

• Typically not done till 14-16 weeks (4 months) into pregnancy

• Results come back slow

What is the significance of the placenta only being present during pregnancy?

Its genetics are identical to the baby’s

Chorionic Villi Sampling (procedure, testing)

• Cells of the placenta are suctioned off, then chromosomes analysed

• Karyogram/type OR biochemical tests can be done

(1) Disadvantage of Chorionic Villi Sampling:

2% risk factor to mother and baby

(2) Advantages of Chorionic Villi Sampling:

• Can be conducted earlier in pregnancy at 8 weeks (2 months)

• Results come back faster

Fetoscopy (when used, procedure, risk factor)

• Only used if reason for alarm, or if you’re making a documentary ig

• Insert a needle-thin camera to mother’s uterus for direct viewing of the baby

• 10% risk factor to mother and baby