Final - Part 2 Flashcards
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Genome vs Genes
Genome: All the genetic material in a norganism
- Ex) genomes of kiwi consist of: nucleus, mitochondria.. bascially everything that is containing heretability).
Genes: a segment of genome that is transcribed into functional RNA (mRNA, tRNA, rRNA) and passed from parent to offspring.
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Where are genomes located in prokaryotes & eukaryotes?
Prokaryotes: in nucleoid (그 nucleus 대신 있는 거)
Eukaryotes:
- Plant cells: nuclear + mitochondria + choloroplast genomes
- Animal cells: nuclear + mictochondria
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How are genomes organized in prokaryotic genomes & eukaryotic genomes
They both have chromosomes.
Prokaryotic genomes: usually in a single circular chromosome.
Eukaryotic genomes: multiple linear chromosomes inside the nucleus.
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Chromosome
Chromatin
Define
Chromosome: a single long chain of DNA of 2 complementary strands.
- Made out of chromatins
Chromatins: A mixture of DNA and proteins that form the chromosome.
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Human genomes
Where? how many?
- 23 pairs of (mostly) homologous chromosomes.
- 46 chromosomes
- Most of our cells’ nuclei
- We should at least have 2 copies of any given gene in similar areas of eeach chromosome.
- Only 1 copy of each chromosome’s sequence is represented in the human genome
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What does homologous mean?
A chromosome is mostly identical in nucleotide sequence to its homomlogous pair.
they can’t be completely identical
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Which chromosome is not homologous?
Sex choromosomes
- Females: XY (not homologous)
- Males: XX (Homologous)
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What human genome project figured out
Most of the human genome is identical between individuals, but there are varations amongst individuals.
This is why wew don’t look the same
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Organization of Eukaryotic Chromosomes
- DNA
- DNA is coiled around histones: protein complex
- Nucleosomes coiled into a chromatin fiber.
- Further condensation of chromatin
- Duplicated chromosome
-> DNA coiled around histones, and these coils are pulled into further coils that help it fit into a nucleus.
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Is DNA always coiled?
DNA can be coiled and uncoiled as needed, so our cells can access the genetic information within.
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Organization of Prokaryotic Chromosomes
- Most prokaryotes’ genomes are one circular chromosome
- May contain plasmids: additional small circles of RNA that could be passed around between different bacterial cells.
- They twist up the chromosomes by the way of proteins and enzymes to fit into the cells.
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How do we physically grow up?
Combination of 2 things
Combination of cells dividing + growing
- Cuz the increase in # of cells make organisms physically grow.
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Cell cycle & 2 broad parts of the cell cycle
Define cell cycle and the parts
Cell cycle: process which describes how cells progress through their lives until division / reproduction
2 broad parts of the cell cycle:
1. Interphase - G1, S, G2 Phases
2. Mitosis + cytokinesis
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Interphase
Describe interphase and 3 major cellular processes
The majority of a cell’s life cycle is spend in interphase
- G1, S, G2
1. General growth (get to a certain size to be able to divide)
2. Replication of chromosomes
3. Preparation for cell division
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G1/G2 Phases
3 major cellular processes
G stands for Gap
1. Gathering up or synthesizing resources for growth
2. General cell growth
3. Growth/replication of organelles
(so that there is enough copied organelles for 2 cells in the future
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Difference between G1 & G2
Cells in G2 have twice as much DNA as cells in G1. Cuz S phrase replicates DNA!
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S Phase
S stands for Synthesis!
1. All the cell’s DNA is replicated
2. New DNA is synthesized
3. All of a cell’s chromosomes are replicated in preparationg for division
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Chromosomes replication during S phase
Don’t confuse the # of chromosomes
- There is an unduplicated chromosome
- Replicated chromosomes attached at the centromere
- While attached these are considered 1 chromosome
- Each half is called a sister chromatid
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After S phase, how many total chromosomes are there in a typical human cell?
46
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Before S phase, how many total chromosomes are there in a typical human cell?
46 (92 sister chromatids!)
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Cell Cyle Checkpoints
How many? why important?
3 Checkpoints: At the end of G1&G2&Metaphase
It’s important to know that the cell is ready to divide. (Are any components damaged? Enough resources in the environment? Are neighbouring cells signalling for or against division?)
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- G1 Checkpoint
- What does it check?
what is it?
It’s the main decision point for cells to progress on cell cycle.
Why? Cuz after this point, a cell is irreversibly committed to dividing cuz DNA is replicated
It checks: internl & external conditions
1. Size
2. Nutrients
3. Molecular signals from neighbours
4. DNA integrity (is any of the DNA damaged?
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G0 Phase
also why does it happen?
Cells may also be cued to leave the cell cycle and stop dividing
- It’s a resting state
- May be permanent or temporary
- Due to: not enough nutrients, neighbouring cells signal against division etc)
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G2 Checkpoint
final check of the genetic material before the chromosomes are separated into 2 cells
Checks:
1. DNA integrity
2. DNA replication (is DNA replication complete)
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DNA Damage Repair & p53
What does the cell do if the dna is damaged?
Proteing p53: Central to DNA damage repair pathways.
- When DNA is damaged, it p53 activates genes that pause the progress through the cell cycle
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What happens if p53 is MUTATE and DNA is damaged in a cell?
Also, if damage to DNA is irreparable, what happend?
The cell progress through the cell cycle and divides anyway with whatever DNA damage it has.
If the damage to DNA is irreparable, cells undergo apoptosis: programmed cell death
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Cancer
What is a cancer and the 2 mutated genes
Cancer: when genes involved in cell cycle control are mutated, causing uncontrolled cell division
Mutations in:
- Proto-oncogenes
- Tumour suppressor genes
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What happens if there are mutations in proto-oncogenes and tumour suppressor genes?
+ is it possible to be born with a mutation on these genes?
Proto-oncogenes:
- Normal gene function: regulate cell growth positively
- 1 mutation is enough
- Acelerates cell growth and division!
- even when it shouldn’t
- 1 copy is mutated! not both of them
- Dominant gene
- Rarely inherited to offsprings
Tumour Suppressor Genes:
- Normal gene function: regulate cell growth negatively
- ex) p53!!
- 1 mutation -> 2nd copy will still provide enough function
- 2 mutations -> loss of function of the cell cycle regulation and NDA repair :(
- Recessive
- More common & responsible for familial cancers.
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M phase - Mitosis & 4 stages
This is just a summary slide of the stages, chill.
Mitosis: Type of cell division making identical cells! nucleus divides!
It’s great for repairing cuts & damage.
Mitosis Stages:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
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Prophase
3 things happening
- Chromosomes are condensed (thickening & visible)
- Nucleus is still there for now.
- At the end of prophase, the membrane around the nucleus in the cell dissolves.
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Metaphase
3 things happening. Don’t forget the key terms
- The chromosomes line up in the middle of the cell and waiting.
- Nucleus is gone!
- The centrioles are now at opposite poles of the cell with the mitotic spindle fibers extending from them.
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M Checkpoint
Checks 2 things
Checks:
1. Are sister chromatids lined up correctly?
2. Is everything attached properly to the mitotic spindle?
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Anaphase
2 things happening
- The chromosomes move away to the opposite poles.
- The sister chromatids are pulled apart.
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Telophase
3 things (?)
- There are full set of chromosomes (46) per end.
- A membrane forms around each set of chromosomes to create 2 new nuclei
- New 2 nuclei forming and starting surround the chromosomes.
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Cytokinesis
Definition & plant cells vs animal cells
Cytokinesis: Division of the cytoplasm and splits the cell in the middle to form 2 separate daughter cells
Animal cells: cytoplasm is pinched apart into 2 by cytoskeletons
Plant cells: a cell wall is made between to divide cytoplam into 2
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Unicellular ≠ Prokaryotic!
Yea
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Unicellular cell cycle
Similarity? differnce?
It’s the same thing but the neighbouring cell signals aren’t really relavent
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- Is apoptosis important in unicellular organisms?
- Cancer??
- Nah. We don’t even think about it
- Not a thing but somethings like that could happen.
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Prokaryotic Cell Division
Difference? 2 things
NO MITOSIS cuz prokaryotes don’t have nuclei.
- Prokaryotes progress through their cell cycles much quicker cuz there is only 1 chromosome and no mitosis
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In unicellular organism, is cell division reproduction?
YES
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2 types of reproduction:
Sexual
Asexual
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What does asexual reproduction do?
Plants?
Asexual reproduction results in new individuals that are clones of each other.
Clones: offsprings are genetically identical (doesn’t LOOK the same though)
Many plants can reproduce asexually. (onions)
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Advantages & disadvantages of asexual reproduction
3 each
Advantages:
1. Only 1 individual needed
2. If the parent is successful, offspring should be successful. (if the environment doesn’t change)
3. Faster growth
Disadvantages:
1. Since they’re genetically identical, if one is disadvantaged, all individuals affected.
2. Lack of genetic diversity
3. What if the environment is changing but yoru genes aren’t changing
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Sexual Reproduction
What should the offspring be/have?
Results in new individuals that are NOT genetically identical to its parents
Offspring should:
1. Be the same species as parents
2. Have the same # of chromosomes as its parents
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What cells are/are not involved in sexual reproduction?
Not all cells are involved in reproduction
Gametes: cells involved in sexual reproduction. Made by germ cells
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if a cell in your stomach gains a mutation, would this be passed to your offspring?
FALSE, it’s not germ cells
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Gametes & Fertilization
of chromosomes
Gametes: cells involved in sexual reproduction
- Usually doesn’t have the same # of chromosomes as the rest of the organism!!
- They have 23
Fertilization: Fusion of gametes that will result in a new individual.
- The union of two gametes (sperm + egg)
- Different # of chromosomes are back to 46
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Different sizes/# of 2 gametes
Female gametes: much larger, fewer
Male gametes: much smaller, more
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Sexual reproduction in plants
Flowers have genders?!
2 types of gametes in plant cells
- Flowers have male & female
- Sometimes this sexual reproduction doesn’t happen in the same flower/same individual.
2 types of gametes:
Pollen: male gamete
OVule: female gamete
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Diploid LIfe Cycle
Haploid Life Cycle
What the heck is that?
Diploid: a cell that contains 2 copies of each chromosome.
- Humans have diploid-dominant life cycle EXCEPT GAMETES
Haploid: a cell that contains a single set of chromosomes
- Sperm and egg cells have 23 TOTAL chromosomes
- Egg(23) + Sperm(23) = 46
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Meiosis stages
Germ cells Interphase -> meiosis (double PMAT)
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Meiosis - Interphase
3 things happen
- Growth
- DNA replication
- General cell processes
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PMAT - 1st Round
P1
- Chromosomes line up in homologous pairs
- They match up!
- CROSSING OVER
M1
- Chromosomes line up IN PAIRS
- Mitosis is a single line
A1
- Chromosomes pulled away by the spindle fibers.
T1
- 2 new nuclei formed
- Ends with 2 new cells
Cytokinesis
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PMAT - 2nd Round
P2
- NO CROSSING OVER
- Basically mitosis prophase
M2
- Chromosomes line up IN SINGLE FILE
- spindle fiber attached
A2
- Chromatids pulled away by the spindle fibers (chromosomes split into 2)
T2
- Nuclei reform
- Cells divide into 2
- 4 new cells in total!
Cytokinesis
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Chromosome # & Chromatids organize
Help so confusiong
Starts with: 46 92
After M1: 23 46 | 23 46
After M2: 23 23 | 23 23
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Meiosis in males / female produce:
Male: sperms
Females: egg
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Nondisjunction
Sometimes chromosomes don’t separate correctly, so a cell could receive too many or too few chromosomes in the separation
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Crossing Over
what does it do & how it happens
Crossing over is the reason why all gametes have differences (why Sally&Kevin don’t look like me)
1. The 2 duplicated chromosomes BOOP each other and exchange the genes.
-> There is always some slight variation naturally ven in the same gene between individuals.
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Haploid-dominant life cycle
Who has that and how to reproduce
Most fungi exist as haploids.
Gametes form from mitosis.
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Errors in meiosis
How? Are organisms good at tolerating this?
Incorrect # of chromosomes in gametes and this becomes more frequent as we age.
ANimals are NOT good at tolerating this :(
Plants are good though
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What happens if an animal carries an extra or less of any particular chromosome?
In general, poorly functioning organism
If extra/less copies of Larger chromosomes:
Inviable embryos :(
If extra/less copies of smaller chromosomes: alive, but disabled
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Why embryos that have problems with smaller chromosomes are more likely to survive than embryos with errors in bigger chromosomes?
Smaller chromosomes = shorter = contains less genetic materials
–> they are more likely to survive than missing more genetic materials
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Triploid plants?!
What is triploid and use banana as an example
Triploid: the cells have 3 copies of every chromosomes
The seedless bananas are triploid!
- 1 diploid parent x 1 quadroploid(?) parent
- We have to use asexual reproduction (clones) to reproduce the bananas.
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Is genetic ariation always a good thing?
NO. As a population, it’s a W
But as individuals, you can result in a combination of genes that don’t go well together.
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Traits
Heredity
Heredity in terms of asexual/sexual reproduction
Traits: characteristics that can vary among individuals in a population
- Ex) blood type, eye colour, height, hair colour
Heredity: traits(genetic materials) from parents to progeny
- Asexual reproduction: identical traits to the parent
- Sexual reproduction: combination of the parents’ traits
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Why did Gregor Mendel choose garden peas to figure out mechanisms of heredity?
4 but not everything is important
- Rapid turnover time (doesn’t take long to see the next generation)
- Easily grown
- Easily distinguishable traits
- Capable of self-fertilization
As long as I got the self-fertilization and rapid turnover, it’s fine
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2 kinds of variables/characteristics of heredity:
and which one did Mendel mainly look at?
- Continuously variable: There is continuous variations of the characteristics (ex) human heights)
- Discontinuous/discrete variable: “Nothing” in between (ex) pea flowers are either purple or white)
- Mendel used discontinuous variable to look at!
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mendel’s experiments
Establishing pure-bred parents(P):
* Pea plants with white/purple flowers
* He made them self-pollinate
* Purple will get purple and white will get white
* This remained for regardless of how many generations.
F1 Hybrid Generation:
* What is we cross-bred these pure-bred plants?
* What people expected is blending of the trait in the resulting hybrids. (expected pink)
* BUT ONLY FOUND PURPLE FLOWERS
F2 Hybrid Generation:
* Made F1 hybrids to self-pollinate
* The WHITE FLOWERS REAPPERAED IN A RATIO OF APPROXIMATELY 3(purple):1(white)!!
* These characteristics applied to ALL 7 characteristics of peas he looked at! (ex) pea shape, pea colour)
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Findings
About 4
- There are dominant & recessive traits
- Each individual have 2 of each gene
- Traits for each characteristics were carried by different versions or variations (Alleles) of these units.
- These units would be separated randomly into gametes.
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Connecting the findings to molecular biology
그냥 그렇구나 하고 넘어가셈
- The heritable materials are DNA
- These heritable units are genes
- The different “versions” of the heritable units are called alleles
- Meiosis segregates alleles into gametes randomly
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What does/how does alleles of. gene produce unique traits?
Different traits are. aused by similar but slightly different versions of protein amino acid sequences
Each version of protein is encoded by slightly different nucleotide sequences
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How do these slightly different versions of proteins arise in the first place?
3 steps
- Mutation happens
- That mutation is inherited into same population of people
- Becomes alleles after certain amount of people have that mutation
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Meiosis - Segreation of alleles
4 steps
- Homologous chromosomes 1 from each parent (P W)
- When it goes on meiosis: DNA replication (PP WW)
- Meiosis 1 divides the pairs (PP <–> WW)
- Meiosis 2 divides all of them (P <-> P <-> W <-> W )
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Homozygous vs Heterozygous
Most organisms have a pair of alleles for each trait (1 from each parent)
Homozygous: both alleles are the same (BB, bb)
Heterozygous: Possess one of each allele (Bb)
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Phenotype vs Genotype
Phenotype: observable traits of an individual
Genotype: Total of an individual’s genetic material
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Laws of Mendelian Genetics
This is a summary
- Law of dominance
- Law of segregation
- Law of independent assortment
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Law of Dominance
- In a heterozygotes, the recessive trait is HIDDEN by the dominant trait.
- The gene product from a single dominant allele is enough to cause a trait
- Dominant trait is NOT always advantageous over a recessive trait
- Proto-oncogene mutation is dominant but it’s not a good thing lol
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Law of Segregation
For a 3:1 ratio of dominant to recessive traits, both alleles must be equally likely to be passed on.
Bb 0.25 BB 0.25 bb 0.25 Bb 0.25
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Law of Independent Assortment
The alleles assort independently in gametes
- Having a particular allele for 1 characteristic doesn’t mean a gamete is more likely to have a specific allele for a different characteristic (ex) 검은 머리라고 피부가 건성일 가능성이 높은게 아님)
- Use dihybrid corsses to prove it
- Meiosis proves that the gametes are segregated randomly
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Other patterns of inheritance - non-Mendelion laws
Just summary
- Incomplete dominance
- Codominance
- Multiple “codominant” alleles
- Linkage
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Incomplete dominance
Don’t forget the key words
Some characteristics of certain species may have intermediate phenotypes in the heterozygotes
- Kind of blending I guess?
- Red flower + white flower = pink
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Codominance
Some characteristics may have both traits show up in the phenotypes of the heterozygote.
- Red cow + white cow = 점박이 cow!
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Multiple “codominant” alleles
Some characteristics may have 3 or more traits with unique patterns of phenotypes in heterozygotes
- Bloodtype!
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Linkage
What does linkage depend on?
Some combinations of alleles that would not separate independently
- Linkage depends on physical distance between genes
- 같은 chromosomed에 있는 gen이면 떨어질 확률이 더 적겠지
