Exam 1 Flashcards
Transmission genetics
- very early concept (meiosis and mitosis)
- early theory of heredity transmission that states specific particles (gemmules) carry information from the body to reproductive organs which are passed to the embryo at conception
Molecular genetics
- replication
- how DNA is maintained … Zooming in
Population genetics
- look across an entire population and observe natural selection
- how population changes through time
Why are Model organisms important
- easy to grow and maintain in a lab, organisms used to study human diseases
Give an example of a model organism
- bacteria
Early theories of heredity
- domestication
- artificial fertilization (Assyrians)
- Hindu writings said they avoided spouses with undesirable traits
1) Pangenesis
2) acquired inheritance
3) preformation
4) blending
Pangenesis
- specific particles (gemmules) carry information from the body to reproductive organs which are passed to embryo at conception
- very early concept of hereditary transmission
- slide 18
Inheritance of acquired characteristics
- early theory of hereditary transmission
- Greeks proposed traits acquired in life incorporated into heredity info and passed on
Ex: an artist would pass his art skills that he acquired during life onto their offspring
Robert Hooke
- discovered the cell using a microscope
Preformationism
- early theory of hereditary transmission
- inside the egg or sperm is a tiny version of an adult (homunculus)
Blending inheritance
- early theory of hereditary transmission
- offspring are a blend of their parents
Schwann and Schleiden
- proposed the cell theory
- > stated that cells are the basic unit of all living things
- > cells arise from preexisting cells
The cell theory
- cells are the basic unit of all living things
- cells arise from preexisting cells
Charles Darwin
- theory of evolution through natural selection
- also wrote the origin of species
- > said that heredity was the fundamental unit of evolution
Origin of species
- heredity was the fundamental of evolution
Gregor Mendel
- discovered basic principles of heredity
- crossed pea plans and analyzed patterns of transmission
Walter Flemming
- first person to observe the division of chromosomes during mitosis
- discovered hereditary information was contained in the nucleus of a cell
August Weismann
- cut the tails off of 22 mice for 22 generations and the tail length of the descendants never changed .. This proved the acquired characteristic theory to be wrong
- purposed the germ plasm theory that said the cells of the reproductive system carry an already complete set of information to be passed down to the next generation
Germ plasm theory
- the cells of the reproductive system carry an already complete set of information
- slide 24
The three major groups of life
1) eubacteria- true bacteria
2) archaea
3) eukaryotes
Prokaryotic cells
- absent nucleus
- small
- one circular DNA molecule
- DNA is not complex
- absent organelles
- absent cytoskeleton
Eukaryotic cell
- has a nucleus
- larger
- multiple linear DNA
- the DNA is complex
- there are membrane bound organelles
- the cytoskeleton is present
Animal vs Plant cell DNA material
Both
- nucleus*
- nuclear envelope*
- Endoplasmic reticulum
- ribosomes
- mitochondria *
- membrane
Plant cell only
- vacuole
- chloroplast*
- cell wall
Are viruses living cells?
- no!
- they have genetic info, but can can only reproduce inside of a host cell
Prokaryotic Cell Reproduction
- binary fission
1) starts with a circular chromosome within a prokaryotic cell
2) chromosome replicates
3) membrane grows, chromosomes separate
4) cell divides, each cell is genetically identical
Eukaryotic cell reproduction
- has 2 sets of chromosomes/cells (as a result of sexual reproduction)
- one set from the mother and one set from the father (homologous pairs)
2 sets of genetic info= diploid (eukaryotic cells)
1 set of genetic info=haploid (reproductive cells)
Homologous pairs of chromosomes- humans have 23 pairs
Ploidy
- the number of sets of chromosomes in a cell, or in the cells of an organism
- each set is designated by n
- diploid or haploid
Diploid
- two sets of homologous chromosomes
- 2n
- one chromosome from mom and one from dad
- most eukaryotic cells (mammals)
- reproduced during mitosis
Haploid
- one complete set of chromosomes
- n
- a cell with half the number of chromosomes found in the nucleus
- reproductive cells (gametes or sex cells)
- produced by meiosis
Chromosome structure includes
- telomere
- centromere
- two (sister) chromatids 👭
- kinetochore
- spindle microtubules
Telomere
- cap on the end of a chromosome that protects from chromosomal rearrangement
Centromere
- in order to get through cell division
- essential for movement of chromosomes in meiosis and mitosis
- lets describe the structure based on where it is located on the chromosome
- one for every chromosome, indicates the number of chromosomes
Sister Chromatids
- Genetically identical chromatids connected at the centromere, considered one chromosome
Kinetochore
- forms around the centromere
- place where spindle fibers connect
Spindle microtubules
- fibers made up of tubular subunits and attaches to the kinetochore from the centre some to pull sister chromatids apart
The 4 major types of chromosome structure
1) metacentric
- centromere is located in the middle of the chromosome
2) submetacentric
- centromere located slights to one side of the chromosome
- has a p-arm=petite smaller end of chromosome
- has a q-arm=larger end of chromosome
3) acrocentric
- centromere is located ALMOST at the end of the chromosome
4) telocentric
- centromere is at the tip of the chromosome
Cell cycle
1) G1 Phase
2) G0 Phase
3) G1/S checkpoint
4) S Phase
5) G2 Phase
6) G2/M Phase
7) Mitosis
8) Cytokinesis
G1
- cell growth, metabolically active
G0
- no dividing stage, doesn’t enter the cell cycle
G1/S checkpoint
- checkpoint makes sure the cell is healthy and not damaged before it enters the S stage
- once you go past the checkpoint the cell is committed to dividing
S Phase
- phase in cell cycle where DNA synthesis occurs
- replicate your DNA (sister chromatids form)
G2 Phase
- phase in the cell cycle where the cell continues to grow and prepare for division
G2/M Checkpoint
- checkpoint in cell cycle in which beyond this point the cell CAN divide
Mitosis Phase
- division of genetic makeup in the nucleus
M or Spindle checkpoint
- in cell cycle the assembly checkpoint after mitosis
M=mitosis phase
Interphase
- the longest stage in the cell cycle
- DNA synthesis occurs
- phase in mitosis where DNA replication occurs
- > G1, S, G2 phases
Cytokinesis
- cytoplasm divides, the entire cell division
Mitosis Phases
- nuclear division-> nucleus divides
1) interphase
2) prophase
3) prometaphase
4) metaphase
5) anaphase
6) telophase
Prophase
- phase in mitosis where chromosomes condense
- DNA is ALREADY replicated
- can see distinct chromosomes
- spindle fibers form from centrosomes(ANIMALS)
Prometaphase
- phase in mitosis where the nuclear envelope disappears which allows microtubules to contact chromatids
- once they contact chromosomes they can move them via centromere to line them up
Metaphase
- phase in mitosis where chromosomes arrange in a single plane called the metaphase plate
- every chromosome is lined up by themselves!
Anaphase
- phase in mitosis where sister chromatids move toward opposite poles and become 2 chromosomes (2n)
- after separation chromatids become chromosomes
Telophase
- phase in mitosis where chromosomes arrive at the spindle poles, the nuclear membrane reforms making 2 nuclei
- chromosomes disappear from view
- Cytokinesis can occur at the same time as telophase
How do chromosomes move during mitosis
- spindle fibers and microtubules change length by the addition or removal of tubulin subunits by molecular motors
- the loss of a spindle fiber can result in the loss or gaining of a chromosome
- if spindle fibers don’t align chromosomes it will result in a syndrome
Ex: some drugs will target spindle fibers Bc if they can not grow or form it will stop mitosis which is good for cancer Bc cells divide when they shouldn’t be
How many divisions does mitosis/meiosis have?
Mitosis- single nuclear division
Meiosis- 2 divisions
What are the results and final ploidy of mitosis/meiosis?
Mitosis- same number of chromosomes that are diploid
Meiosis- newly formed cell has half the number of starting chromosomes that are haploid
What is the final product of mitosis/meiosis?
Mitosis- yields genetically identical cells
Meiosis- yields genetically variable cells
Homologous pairs
- pairs of chromosomes alike in structure and size that carry genetic information for the same character (2n)
Meiosis Phases
Meiosis 1 1) Middle Prophase 1 2) Late Prophase 1 3) metaphase 1 4) anaphase 1 5) telophase 1 Meiosis 2 6) prophase 2 7) metaphase 2 8) anaphase 2 9) telophase 2
Middle prophase 1
- phase of meiosis where chromosomes condense and spindle fibers form
Late prophase 1
- phase of meiosis where homologous chromosomes pair, synapsis (very close association)
- bivalent/tetrad-> 2 different chromosomes attached in a way
- crossing over occurs where there is an exchange of genetic info
- crossing over occurs at the chiasma
- the nuclear membrane breaks down
Metaphase 1
- phase of meiosis where homologous pairs of chromosomes align along the metaphase plate
- microtubules attach to one pair from each pole
Anaphase 1
- phase of meiosis where homologous pairs of chromosomes are separated
- PLOIDY is reduced
Telophase 1
- phase of meiosis where chromosomes arrive at spindle poles and cytoplasm divides
- interkinesis-> nuclear membrane reforms, DNA relaxes
Prophase 2
- phase of meiosis where chromosomes recondense
- nuclear envelope breaks down
Metaphase 2
- phase in meiosis where like metaphase of mitosis chromosomes align on the metaphase plate
Anaphase 2
- phase of meiosis where sister chromatids are pulled apart and are now chromosomes
What are the consequences of meiosis?
1) each cell produces 4 cells
2) chromosome number is reduced by half
3) cells produced from meiosis are genetically distinct
Telophase 2
- phase of meiosis where chromosomes arrive at the spindle pole
- the nuclear envelope reforms
- the cytoplasm divides
Why are the cells produced from meiosis genetically distinct?
1) crossing over yields sister chromatids that are not identical
2) random distribution of chromosomes in Anaphase 1 (can line up in any orientation)
Difference between meiosis 1 and meiosis 2
- meiosis 1 is reduction division
- meiosis 2 is the mitotic division
Crossing over
- exchange of genetic material on homologous pairs at the chiasma
- at the end all chromatids become genetically distinct
What would happen if crossing over occurred between 2 sister chromatids?
- the genetic outcome would not change, they balance themselves out
How many chromosomes do humans have
- 23 chromosomes
Female gametogenesis (oogenesis) process
- first meiosis 1 occurs after the primary oocyte (2n) develops
- this results in an unequal cytokinesis that produces a secondary oocyte (1n) and first polar body
- meiosis 1 stops in prophase 1 and is restarted by ovulation
- then meiosis 2 occurs after the secondary oocyte (1n) and the first polar body are formed
- this results in another unequal cytokinesis that produces an ovum (1n) and a second polar body
Explain why the meiotic divisions in oogenesis involve unequal cytokinesis
- so that one daughter cells gets all the cytoplasm, while the other gets only extra chromosomes and becomes a polar body in the ovum that will be reabsorbed
- having one cell get all the cytoplasm allows for that cell to more fully prep for an embryo
Mendel
- the father of genetics
- wanted to understand how our traits passed from one generation to the next
Gene
- a genetic factor (region of DNA) that helps determine a characteristic
- from Pangenesis
Allele
- one of two or more alternate forms of a gene
Ex: round seed vs a wrinkled seed
Locus
- specific place on a chromosome occupied by an allele
Genotype
- set of alleles that an individual possesses
Heterozygote
- an individual possessing two different alleles at a locus
Homozygote
- an individual possessing two of the same alleles at a locus
Phenotype or trait
- the appearance or manifestation of a character
- genotype and environment (only genotype is inherited)
Character or characteristic
- an attribute or feature
Why were Mendels pea plants a good choice
1) pea plants good subject easy to grow, grow rapidly and produce many offspring
2) had genetically pure stocks of different types of peas to start studies
3) avoided characters that exhibited variation
4) used an experimental approach- hypothesis driven research
Monohybrid cross
- cross where parents differ in a single characteristic
Ex: 2 plants that are breeding true that have opposite alleles (yellow seed vs green)
Reciprocal cross
- cross where crossing in the other direction to make sure that the sex of the parent doesn’t influence the outcome of the new plant
Backcross
- cross where you take one F1 generation plants and cross with a P generation plant, gives a 1:1 ratio
Dihybrid cross
- crosses or organisms that differ in two characteristics, results in a 9:3:3:1 ratio
Test cross
- cross individual of unknown genotype with a homozygous recessive to help determine the unknown genotype
Mendel concluded 3 things
1) unit factors in pairs -> each trait has 2 different unit factors that result in different traits, gives 3 possible combinations
2) dominance and recessiveness
3) segregation
All 7 characteristics that Mendel studied yielded what ratio in the F2 generation?
- yielded a 3:1 ratio
Dominance vs Recessive traits
Dominance- traits that were observed in F1
Recessiveness- traits that disappeared
Principle of segregation
- Mendels first law
- two alleles separate when gametes are formed, one allele to each gamete
- upon fusion at fertilization, zygote gets one allele from Both a male and female parent
- separate with equal probability into gametes
Using a test cross if a tall pea plant could be either Tt or TT how do you know which?
Cross TT x tt
If TT -> all tall F1= Tt(tall)
If Tt-> F1 will be Tt (tall) and tt (short) in a 1:1 ratio
Principle of independent assortment
- Mendels second law
- alleles at different loci separate independently of one another
- the characters must be located on different chromosomes (as assortment is related to chromosome separation at anaphase 1)
Punnett square
- for a dihybrid cross, more than 2 loci
- developed by RC Punnett
Genotypic ratio
- for simple genetic crosses for the F2 generation if the type of dominance in a trait is incompletely dominance
Genotypes of parents Aa x Aa 1:2:1 ratio 1/4 AA , 1/2 Aa, 1/4 aa
Phenotypic ratio
- for simple genetic crosses of the F2 generation if the type of dominance in a trait is comp,rely dominant
Genotypes of parents
Aa x Aa
3:1 ratio 3/4 A and 1/4 aa
Branch diagram
- can obtain genotypic and phenotypic ratios
- by setting out the proportions of genotypes and phenotypes for each allele pair and connecting these proportions of the other allele pairs, a branch or web of genotypes or phenotypes can be constructed
Multiplication rule
- the “and” rule
- to use this rule the events must be independent
Addition rule
- the probability of one of two or more mutually exclusive events is calculated by adding the probabilities of the two events
- the “either” “or” rule
Walter Sutton and Theodor Boveri
- discovered that homologous pairs of chromosomes consist of one maternal and one paternal
- developed chromosomal theory of heredity
- homologous pairs segregate independently at meiosis
Chi Square (X^2) Test
- used to determine the probability that the difference between the observed and the expected values is due to chance
- if P >_ .05 difference likely causes by random chance
- if P < .05 assume chance is NOT responsible and a significant difference exists
X^2 Analysis formula
X^2= sum of (#obs-#exp)^2 / # expected
- for all classes
- then compare to critical values at specific P (.05) and degrees of freedom
Degree of freedom
Df= n-1
n= number of different phenotypes
Pedigree
- pictorial representation of a family history
- draw the family tree
What is the difference between meiosis 2 and mitosis?
- meiosis 2 has only one copy chromosome 1
- mitosis has 2 separate cells undergoing it at the same time
Proband
- first KNOWN. Affected family member
Consanguinity
- mating between related individuals (incest)
Autosomal Recessive Trait
- appears in both sexes with equal frequency
- trait tends to skip generations
- affected offspring are usually born to unaffected parents so look bottom up
- when both parents are heterozygous 1/4 of offspring will be affected
- appears more frequently Among the children of consanguineous marriages
Autosomal dominant traits
- appear equally in both sexes
- both sexes transmit their trait to their offspring
- unaffected parents do not transmit to offspring
- affected must have at least one parent with it to be dominant
- it will NOT skip a generation
- most affected have a heterozygous genotype
- when one parent is affected (heterozygous) and the other parent is unaffected 1/2 will have it
Pedigree
- pictorial representation of a family history
Identification of pedigrees symbols
- male(square), female(circle), unknown(diamond)
- affected with traits (filled in)
- carrier that doesn’t have the trait (dot in middle)
- may later exhibit the trait (line down middle)
- deceased (line through it)
- cousins (2 lines)
Allele
Wild type allele and a normal allele
Loss of function mutation
- reduced productivity of gene product
Null allele
- no productivity of gene product at all
Gain of function mutation
- increased (extra) productivity or new function
Neutral mutation
- change to distinguish one allele from another, no phenotype change
Identifying allele mutations
- wild type vs mutant
- superscripts
1) wild type (+) most common, not always the best
2) mutant (-) just Bc mutant doesn’t mean it’s worse
3) superscripts distinguish alleles
Incomplete dominance
- cross a homozygous true breed parents (P generation) and get a hybrid for F1
- cross F1. To get F2 and can see which is dominant and which is recessive
Ex:
P generation= PP(purple) x pp(white)
F1 generation= Pp(violet)
F2 generation=PP(purple), pp(white), Pp(violet)
Codominance
- MN blood types: antigens on red blood cells
- two alleles L^M and L^N
- possible genotypes LM LM, LM LN, LN LN
- possible phenotypes
LM LM only produce M antigen
LN LN only produce N antigen
LM LN produce both M and N antigens
Lucien Cuenot
- showed Mendels principle applied to animals
- lethality is recessive
Dominant lethal- one copy that causes death is huntingtons disease
Pleitropy
- one gene that impacts several aspects of the overall phenotype
Multiple alleles
- can be many different alleles for one gene in the general population
Ex: ABO blood group
I^A- codes for A antigen
I^B- codes for B antigen
i- codes for no antigen
AB= individual has I^A and I^B allele O= has neither of them so ii
Gene interaction
- genes at two loci interact to produce single characteristics
Recessive Epistasis
- the hypostatic gene is hidden … all black traits
- Epistasic gene is all lowercase recessive
Which makes a black and brown dog turn yellow
Bombay phenotype
- rare mutation (recessive Epistasis)
FUT1 fucosyl transferase
- H antigen
- necessary for A and B antigens to be added to RBC
- hh individuals type as O, but can NOT receive O blood (hides A and B)
Dominant epistasis
- first gene masks hypostatic gene, only one dominant allele
- different phenotypic ratios
Complementation
- determining if mutations are on the same or different loci
- cross homozygous recessive mutants
- if mutation is the same gene =homo recessive
- if mutation is a different gene= compliment to eachother, wt on each gene
