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Unit 1
> encode the phenotype
Mendel's work is first published 1866
Griffith transforming principle
Chargaff base pair equivalencies 1948
Avery, Mac leod, McCarty DNA 1944
it's accepted that DNA is the genetic material
Ashbury → Wilkins t Franklin X-ray diffraction
Watson+ Crick Proposed DNA model 1953
Levene's tetranucleotide theory 1910
Levene
Griffith
worked with smooth t rough strains of streptococcus
- rough = non-virulent = mouse lived
- smooth= virulent = mouse died
added heat killed smooth strain and mouse lived added heat killed smooth strain and rough strain and mouse died
- streptococcus cells were found and were similar to smooth strain
proposed that the four nucleotides were always together did not account for that DNA could hold complex information
1900'S
Mendel's work is rediscovered
Avery, Macleod, McCarty
determined that the molar amount of A nucleotides were equal to the moral amount of T nucleotides
- same with C and G A and T are base pairs, so are G and C
Chargaff
treated heat killed smooth strain with enzymes that would destroy proteins, RNA, and DNA respectively each respective sample had rough strain added to it only the sample with DNase did not produce virulent bacteria DNA is what transfers information
used X-ray diffraction to determine the shape of DNA
- determined it is long, skinny, with similar parts parallel to each other
- also is helical
Ashbury → Wilkins and Franklin
> ability to replicate faithfully
> have the ability to vary
> contain complex information
4 characteristics of genetic material
Chromosomes, cellular reproduction, and DNA structure
P
BASE
HEiti
s (^) z
5 o (^2) Base
Base G T C CT^ A^ GT CA GGA^ T^ CA 3 5 3
Nucleotides
Phosphate deoxyribose base ( G C A T )
Purine
Pyridines
Phosphate group
Bases
5' vs. 3'
Structure of DNA
Writing and drawing DNA sequences
show 5' and 3' ends show bases should be two lines (^) > Show all the parts bases can be “ base” label the 5’ and 3' ends
The 5vs.3 prime ( ‘ ) is determined by Carbon placement
- the carbons are labeled in purple
if the first strand starts with a 5' then the anti parallel strand will start on the 3' end
Genetic information is stored in chromosomes in both prokaryotes and eukaryotes
have linear chromosome arrangement the number of chromosomes varies between eukaryotes, but will always be even divides by meiosis (germ cells) or mitosis (all other cells)
Eukaryote
have a singular circular chromosome divide by binary fission
Prokaryote
Chromosomes and cellular reproduction
Deoxyribose (sugar) backbone
hydroxyl group to phosphate group = phosphodiester bond second backbone is anti parallel nucleotides are attached by hydrogen bonds
Stages of mitosis
Interphase
sister chromatids are connected but not condensed
Prophase
nuclear envelope breaks down DNA condenses spindle fibers from the centrosomes attach themselves to the chromosomes from each pole of the cell
Cytokinesis
cell divides into two cells.
Anaphase
The sister are pulled apart and to
different poles of the cell.
Telophase
chromosomes reach the poles nuclear envelopes form DNA decondense
Mitosis results in two genetically identical cells
Chromosomes (^) Nuclear DNA molecules
46
Metaphase
chromosomes line up at the metaphase plate (equator of the cell)
Kj
EFFI
Ei te
Ei EI
FEI It
I EK
Prophase 2
nuclear envelope breaks down DNA condenses spindle fibers from the centrosomes attach themselves to the chromosomes from each pole of the cell
Metaphase 2
chromosomes line up at the metaphase plate (equator of the cell)
Prophase 1
nuclear envelope breaks down DNA condenses into chromosomes homologous chromosomes line up to form tetrads crossing over: chiasmata form between non-sister chromatids spindle fibers attack to each chromosome
Meiosis Chromosomes (^) Nuclear DNA molecules
46 92
Metaphase I
homologous pairs line up along the metaphase plate
Anaphase 1
homologous chromosomes are separated from each other
Telophase 1
chromosomes decondence nuclear envelope reforms cytokinesis occurs resulting in two cells
Selfing Transferring the pollen of flower 1 to the stigma of flower 1
Cut off flower Z anthers, transfer the pollen on flower 1 anthers to flower Z stigma
Cross pollination
Mendel wanted to know what would happen if he crossed two true-breeding plants, each with a different phenotype of a trait.
Are used to determine the progeny of a cross as well as their frequency They come in different sizes depending on the traits being looked at
Genotype of parent 2
Genotype of parent 1
Genes are in pairs, and they segregate from each other during gamete formation
Homologous chromosomes segregate during meiosis, carrying gene pairs with them
Gene pairs located are on homologous chromosomes
Alleles at different genes separate into gametes independently of one another
The P generation ( parental generation) consisted of a true breeding (TB) round seed plant and a TB wrinkled seed plant The FI generation (offspring of the parental generation) had all round seeds
he allowed the F1 generation to self fertilize The F2 generation (offspring of the F1 generation) had 3/4 of the seeds being round and 1/4 of them wrinkled
From this experiment he created his first law: the principle of segregation
Punnett squares
- Genes come in different forms, these different forms are called alleles
- Genes for a trait come in pairs
- Alleles do not mix in an individual, during gamete formation they separate so each gamete has 1 allele
- When two different alleles are present...
one is the dominant allele = the one that determines the phenotype one is the recessive allele = the one that's present, but unexpressed
Genetic Locus: another word for gene (plural = loci)
makes the point that genes are found in a particular location on a chrome some
This was determined from the results of an experiment he did where two homozygous (one for round, yellow seeds and the other for wrinkled, green seeds) plants were crossed
Mendel's second law
Modern corollary: genes on different chromosomes assort independently
Genotype: the two alleles of a gene that an individual has Dominant alleles = capitalized Recessive alleles = lowercase Homozygotes: individuals with two of the same alleles Heterozygotes: individuals with two different alleles
Dihybrid punnet square is one that's looking at the possible genotypes at two parents who are both heterozygous for two traits Possible gametes of parent 1 Possible gametes of parent 2
Ry RY rY ry
RR yy RR Yy Rr Yy
Rr Yy
Rr yy
Rr yy Rr YY Rr Yy
Ry RY rY ry RR Yy RR YY
Rr Yy
Rr YY rr yy
rr YY rr Yy
rr Yy
He determined that the F2 generation would always have the ratio 9:3:3:
q = double dominant, 3‘s = heterozygous, and 1 = double recessive
Results
The usual version at a gene model organisms: referred to as "Wild type” humans: "typical” or “usual" The different version at a gene model organisms: referred to as "mutant” humans: "variant” or “atypical"
Allele terminology
However, being wild type or mutant does not determine dominant or recessive
Used in genetics to predict the outcome of a genetic cross
> It can be applied to complex problems where multiple traits are being considered
Multiplication rule: the probability of two or more independent events occurring together
> Calculated by: multiplying their independent probabilities
OR
What is the probability of getting all recessive trails in a cross between the following:
Aa Bb Cc Dd Ee x Aa Bb Cc Dd Ee
aa = 1/4 bb = 1/4 cc = 1/4 dd = 1/4 ee = 1/
answer = 1/
3/4 yellow 3/4 X 3/4 = 9/ 3/4 round 1/4 green 3/4 x 1/4 = 3/ 3/4 yellow 1/4 X 3/4 = 3/ 1/4 round 1/4 green 1/4 x 1/4 = 1/
Notice the results show a 9:3: 3:1 ratio
Probability:the likelihood at the occurrence at a particular event
> multiplication rule
> addition rule
Probability
Molecular basis at genetic change
How do changes in the DNA lead to trait differences?
Mutant alleles can be described in multiple ways.
Singe base changes can result in multiple mutations
4. Describe how allele behaves compared to another allele
1.consequences of point mutations
**2. Location of the mutation
- Describe the effect the DNA Chang has on the function of the gene product**
-The mutation is dominant to the recessive allele-can ten cause the rest of the groups to not function right
Silent mutation: mutation that haas no effect on gene structure Amorph: mutation that causes the gene to completely lose function Hypomorph: reduces the amount/ effectiveness of encoded gene product Antimorph: has dominant interfering action on a wild-type allele -seen in hetrozygote situations
Hypermorph: increases the amount of encoded gene product - too much = bad Neomorph: causes a new function of the product
Every gene is haplosufficient or haploinsufficent Haplosufficant: even at 50% half is enough to do the job. Haploinsufficent: at 50%, half is not enough
the location of a mutation can help predict its consequences
- Synonymous, missense-conservative, missense-nonconservative, and nonsense
- Nonsense, insertion, and deletion are all equally bad
Non-gene regions: usually little or no consequences Promoter/regulatory sequences → important for getting the gene transcribed Exons → encode protein -Active sites: if the active site isn't shaped correctly ) -More important sequences within protein coding Introns→ end up being cut out = less important
- Haplainsufficenty - The dominant ( AA, Aa) will show mutant and a/a will show wild type
- dominant interfering action of variant allele on the wild type / typical protein -when the produced protein is part at a larger whole- it effects the whole
- Variant protein cannot be properly regulated
Dominant variant alleles:
Recessive variant alleles: usually amorphic mutations, and the single wild type/typical allele is sufficient to carry out the job
normal rules of dominance apply when you have two X chromosome Make sure to include x-y only if needed
Controlled mating is not possible long generation time small family size
Pedigrees and sex -linked inheritance Writing crosses with sex chromosomes indicate chromosome type and indicate the allele as a superscript
Pedigree: picture representation of a family history, a family tree that outlines the inheritance of one or more characteristics Key Filled in= effected by condition Slashed = currently decreased Roman numerals = generation,
Circle = female Square = male Diamond = non-binary or unknown gender Arrow with "p" (proband) = person coming to the genetic counselor
A persons gender is used to create the pedigree and notes are added if needed
F: this pedigree shows that two women married and used a surrogate (S) and a sperm donor (d) to have a child. The dashed line from one of the mothers to the child shows that they are related, just not genetically
D:
first diamond = female transitioned to non-binary 2nd diamond = male transitioned to non-binary
Challenges in studying humans genetics
Pedigrees
Alternative family structures are indicated on pedigrees "Egg parent", "sperm parent", FTM (female transitioned to male), MTF
