Inheritance (copy)

Genetics: the study of inheritance (genes, DNA, chromosomes)

Genes:units that code fro traits

Heredity: the passing of traits from parents to offspring

Allele: “option” for a gene

^^ACTG^^ ==ACTG== ACTG

Types of traits

  1. species traits - all members of the species have certian genes eg; the ability to walk requiresthe correct traits
  2. individual triats - makes you different from others eg; eye, colour, hait colour, taco tongue

Gregor Mendel “Father of Genetics” (1865)

-experimented with pea plants

Polination

-stamen(male reproductive organ in plants) produces pollen→ transferred to the pistil(female part of plants) where egg is produced→ fertilization occurs, producing the seed

Self Pollination

-plant transfers pollination to its own pistils; offspring are genetically identical to parent

Cross Pollination

-pollen is transferred from 1 plant to another; offspring may look different from parent

Mendels hypothesis/laws/princibles

  1. inherited traits are controlled by facotrs(genes) occur in pairs
  2. one factor in a pair may mask the other
  3. a pair of factors is seperated when gametes form, so heterozygotes produce equal number of gametes that have different alleles
  4. factors from a pair are seperated and distributed independetly of the way other facotrs are distributed

Homozygote: GG/gg

Heterozygote: Gg

homo=same, hetero= different

%%Genotype%%: the actual genes in an organism eg; TT, Tt, tt

^^Phenotype^^: the physical presentation/expression of a gene

%%TT%%→(pure) ^^tall^^ Homosygous Dominant

%%tt%%→ (pure) ^^short^^ Homosygous Recessive

%%Tt%% → (hybrid) ^^tall^^ Homosygous Dominant

Alleles are different forms of a gene that have different effects on a trait eg; T an t are both alleles fot height will not affect colour

Punett Squares

-help determine the probability of an offspring having a certian genotype or phenotype

-based on parental phenotype

-probability-branch of math associated wiht predicting the results of chance events

ex; a homosygous tall is crossed with a homozygous short pea plant (TTxtt) ___

ex; of a heterozgous plant crossed with a heterozygous plant ____

monohybrod crosses

-single trait gene crosses - 1 pair of contrasting traits

ex; seed shape Round is dominant (R), Wrinkled in recessive (r)

pure round x pure wrinkled ___

Genotypes: all Rr (ratio) or 100% Rr

Phenotypes: all Round or 100% round

F1 cross: Heterozygous round (Rr) x Hybrid (Rr) ___

Genotypes: 1RR, 2Rr, 1rr / 25% : 50% : 25%

phenotypes: 3 round, 1 wrinkle / 75% round : 25% wrinkled

Test Cross

- cross an organism of an unknown gentotype with a HOMOZYGOUS RECESSIVE INDIVIDUAL

- resultining ratio will allow you to determine the genotype of the unknown individual

*only works if pattern of inheritance follows simple medelian genetics

ex; purple floweres are domnant to white flowers, purple flower couls be PP or Pp ___

*if ratio is 1 : 1 we know the individual is heterozygous/hybrid

*if ratio is 100% we know the individual must be homosygous/pure

Moving Beyond Mendel

Incomlete Dominance: hybrid phenotype is a mix (shows as inbetween) of the pure breeding phenotypes

ex; snap dragons

RR → Red

Rr → Pink

rr → White

NO DOMINANCE ___

F1 cross Rr x Rr ___

2 Rr

1 rr

1 RR

True Breeding Strain: Breed together and ALWAYS get the same thing you started with

*offspring will always resemble parents in that trait

RR x RR rr x rr Rr x Rr

 RR                        rr                          1 : 2 :  1

True True hybrid

Codominance: both alleles are expressed in an individual

ex; human blood test A, B, AB, O

Multiple Alleles: more than 2 alleles exist for a trait

ex: human blood type

Ia Ib io Type A = AA or AO

a and b are codominant with each other B = BB or BO

a and b are dominat over o AB = AB

                                                                                            O = OO

Carrier: hybrid, contian usually a disease that is recessive for you ex; fruit fly eye colour

selective breeding: crossing desired traits to produce an offspring with certain characteristics

*includes inbreeding→ similair traits to produce offspring with certain characteristics

Breeding ex; pure breed dogs

Hybridization- blending different raits to produce new offsring like apple tree

probability: study of outcomes

rule #1 each event is individual

#2 product rule- the chance of more than 1 event occuring simultaneously us equal to the product of the events accuring seperatly

Dihybrid Crosses

-2 trait crosses

*these traits are independant

ex; coed shape (R,r) and seed colour (Y,y)

-making gametes: foiling ___

Round: RR or Rr Yellow: YY or Yy

Wrinkled: rr Green: yy

P1 RRyy x rrYY (round/green) x (wrinkled/yellow)

Gametes: Ry, and rY

Genotypes: all RrYy

Phenotypes: all round + yellow seeds

F1 cross ___

9:3:3:1 ratio

9 round/yellow

3 round green

3 wrinkled yellow

1 wrinkled green

Polygenic traits

-different genes can interact to control the phenotype expression of a single characteristic

eg; skin tone, eye colour, height, h=kernelll colour of wheat

Epistasis: interaction between 2 genes that modify the phenotypic expression of the other

*can result in phenotypic ratios form dihybrid crosses to deviate from the 9:3:3:1 ratio

eg; albanism in humans - a single gene that masks all other genes related to skin, eye, hair colour

eg; fur colour in dogs

Bbww x bbWw G P

B → black bbWw 2 White

b → brown BbWw 1 black

W → prevent pigment bbww 1 brown

w → doesnt prevent pigment Bbww

Complementary interaction - 2 gene pairs produce a trait that neigher could produce by themselves

ex; chicken combs

P1 RRpp x rrPP

f1 gen: RrPp

f2 cross ____

9 wlanut

3 rose

3 pea

1 single

pleiotropic genes: 1 gene that appects many characteristics like marfan syndrome

Lethal alleles: gene/allele that leads to the death of an individual, can be dominant or recessive like huntingtons disease(dom)

-deecrtive huntington protein in the brain

Symptoms: involuntary movements, decline in thinking/rational reasoning, mood changes

*eg; adreanaleukodystrohy (ADL) → recessive+sexlinked

-damage of myelin sheeth in neurons

Mutation: change in the genetic code

  1. gene (point) mutation → base in DNA has changed, like a genetic typo
  2. chromosomal mutation → caused by nondisjunction, crossing over, or less of some/all of a chromosome

Causes: Chemicals, Radiation, Temperatire, Replication errors

a. somatic - affects body cells

-a new trait may appear

*is not passing onto an offspring

b. germline - affect reproductive cells

-does not get passed to an offspring

causes: chemicals, radiation, temperatire, replication errors

Environmental Influence

traits can be altered/changed due to environmental effects like himilayan hair colour

-normal = white with black nose, ears, tail, and feet

*remove a bit of white hair and cool the area wiht an ice pack, the new hair growth will be black

Conclusion: hair grown on warm body is white colour, extremity is black

Gene action: when genes interact with environment

*phenotypes are often a blend of nature (gene) and nature (environment)

Twins

1. Fraternal → develop from 2 differnet eggs fertilized by 2 diff sperm ___

-hyperovulation

-genetically these are siblings - genes are still very different

  1. Idenitcal → develop froma single fertalized egg that splits into 2 cells

-genetcally identical - genes are the same

-chance event after vertilization

Blood Type

antigens A,B, none

4 possible blood types (phenotypes)

Rh factor

-Rh protein may (+) or may not (-) be present on RBCS

-Rh+ people→ no anti-Rh antibodies

Rh- people → also have o nati-Rh antibodies, but likely can acquire them

can cause issues during childbirth

  • Rh+ dominant over Rh-

Odd things to note regarding X-linked traits

Females have XX Males have X (Y)

-2 copies of x linked genes 1 copy of x linked genes

*if both Xs were active in the female, theyd produce 2x as much protein in comparison to males

  • to compensate, 1 X chromosome is (randomly) inactivated in every single cell

-all genes on that chromosome are inactive

-inactivated chromosome is highly condensed; called a barrbody

Moleculat genetics

the road to discovering DNA as the genetic material (1800s)

  • Fredrich Mieschur
    • discovered DNA in 1869
    • “nuklien” because it was found in the nucleus in the cells
  • walter flemming
    • introduces the term “chromatin”
    • nuclein + chromatin turned out to be the same thing
    • by the 1900s it was understood that chromatin consisted of DNA and proteins
    • major dissent to which was 2 genetic material

PAT levine thought SNA was too simple

  • 4 bases (adenine, thymine, cytosine, guanine) were not enough to determine lifes code
  • “tetranucleitide hypothesis” protein was more liley genetic material - diversity fo amino acids +combinations leads to much more complex folding patterns

DNA vs Protein : which one?

  • hereditary molecule must be able to … control protein and enzyme production

    • why enzymes? necessary catalysts that enable cells to survuve long enough to produce by assisting chemical reactions
    • why protein? they maje up enzymes, necessary building blocks to cell structure
    • self replicate accuratly
    • hereditary material must be able to copy itseld accuratly so the daughter cells can continue to function properly

  • Change (mutability)

    • becuase organisms (at the population level) change over time (adapt) → their genetic material must be able to change, especially is this change is passed from generation to generation
    • be found in nuclues

    - without a nucleus a cell cant undergo division

Griffithis Experiment (1928)

  • used pnenimococcus bacteria (causes pneumonia)
  • smooth (s)→ smooth coats, caused pneumonia in mice
  • rough (R) →rough coats, did not cuase pneuomonia in mice
  • heat killed both S and R strains
  • when injecting mice with the heat killed bacteria they didnt get pneuomonia
  • then when injecting with heat killed S type and living R type the mouse got pneumonia
    • the bacteria isolated from the mouse was licing S type
  • the living R type bacteria which was normally non-violent combined with somethig from the heat killed s type was transofrmed to give virulent s type off spring

Avery, McCarty and Macleods Expirement (1940s)

-Adapted Griffithis experiment to isolate and control more variables to find the transforming princible

  • transormation did not occur if DNA wasnt present

  • transformation did not occur if enzymes were used that destroyed DNA molecule

  • transformation COULD occur even if proteins were denatured

    therefore DNA is the molecule that controls hereditary