Lecture 3 Flashcards
Understand molecular biology, selection mechanisms, and speciation
Pangenesis
that every cell in the body generates an invisible blueprint of itself (gemmule) and stored in the reproductive cells (gametes)
REJECTED
Blended Inheritance
Theory passed on by Darwin
offspring were a uniform plant of it’s parents characteristics and each parents contributes to the gemmules of the offspring equally
Gregor Mendel
explained inheritance of traits by using plants
Figured out there was a mathematical ratio that you could use in order to figure out the phenotype and genotypes off offspring
Able to identify which genes were dominant and which were recessive by using self breeding and cross breeding plants. F1 generation were all heterogenous plants and then when crossed again there was a 3:1 ratio of dominant to recessive phenotypes
Allele
one of more variant of a gene
ex: the seed can be wrinkled or smooth
principles of segregation
principle deemed by Gregor Mendel
genes occurs in pairs, then they segregate from each other during cell division and results in each gamete having 1 copy, so when fertilized there will be 2 copies again for the daughter cell
principle of independent assortment
Gregor Mendel
the distribution of one pair of alleles does not influence the distribution of any other pair of genes (ie just because the seed is wrinkled doesn’t mean that it will always be yellow)
EXCEPTION: if the genes are very close together on the same chromosome they tend to assort together
Genetics:
study of genes and how traits are transmitted from one generation to the next
Gene
sequence of DNA that codes for a protein
Prokaryote
single celled organism that has no nucleus
bacteria and blue-green algae
Eukaryote
Have a nucleus that contains DNA
can be mutlicelled or single celled but must have a nucleus with DNA
composed of carbohydrates, lipids, nucleic acids and proteins
DNA
deoxyribonucleic acid
Discovered by Watson, Franklin, and Crick
Formed of nucleotides that contain a phopshate, sugar, and 1 of 4 bases which are A, T, C, or G. adenine, guanine, cytosine, thymine. A goes with T, C goes with G
backbone is the phosphate bound to the sugar
Double stranded
DNA is found in long condensed strand in chromosomes and in the nucleus of the cell
only 1.5% of DNA is coding while everything else is noncoding - variation lies within the alternative splicing of introns to turn genes on and off
mtDNA
Mitochondrail DNA
only found in the mitochondria of the cell and it gives energy to the cell
is only inherited from the mother
Replication of DNA
1) dna is separated via the H bonds
2) single strand DNA is replicated into mRNA
3) mRNA leaves the nucleus and goes into the cytoplasm
4) Ribosome attaches to mRNA and reads it attracting tRNA that have the anticodon for the codon of the amino acids attached
5) tRNA waits for their 3 codon triplet to appear and then attaches the amino acids together to make a polypeptide
6) polypeptides are proteins
7) proteins serve as functions
Mutations that can occur
Point mutation: SNP, occurs in translation of mRNA to amino acids. Deletion: deletion of a base Insertion: insertion of a base Inversion: DNA is reversed other: sunlight, chemicals, radiation
Intron Splicing
Introns are considered junk DNA, do not code for any proteins, they just turn genes on and off via the alternative splicing
Introns are spliced at certain places for the exons to connect and code for proteins
Allows for variation
Sickle Cell Anemia
point mutation that has an A instead of T producing valine instead of glutatmic acid
This causes the hemoglobin protein to not be in the same 3D shape as a normal hemoglobin and so it does not carry oxygen well or at all. This causes cells to die
We see sickle cell anemia selected for in areas of Malaria because the malaria cannot attack the hemoglobin the same way and cause the same effect, making sickle cell anemia patients resistant to malaria
Industrial Revolution
more pollution in the air caused the trees to go from light to dark which cause epigenetic in the moths to change their body color from light to dark in order to hide from predators
also known as industrial melanism: increased pigmentation resulting from human modification of the environment
Functions of Proteins
Enzymes: catalyze chemical reactions (lactase)
Structural proteins: give structure and support tissues (keratin)
Gas transport proteins: carry vital gases to tissues (hemoglobin)
Antibodies: part of immune system (Anti-A)
Hormones: regulate metabolism (insulin)
Mechanical proteins: carry out specific functions or work (mysoin)
Nutrients: provide nutrients to tissues (ovalbumin)
Mitosis
only in somatic cells
asexual reproduction
1 cell division
Prophase (DNA is duplicated) diploid
Metaphase (homologous pairs align at the middle of the cell)
Anaphase (homologous pairs are pulled apart to opposite ends of the cell)
Telophase (cell is cut into 2) cells are still diploid
Meiosis
in gametes (sex cells)
sexual reproduction
oogenesis occurs in oogonia and resulting in 1 vital ovum and 3 polar bodies
spermatogenesis occurs in spermatogonia and results in 4 vital gametes
2 cell divisions
crossing over/recombination occurs in metaphase 1
Gametes end after telophase 2 in haploid form.
Chromosomes
condensed form of DNA that is only found in the nucleus
has a centromere which is a constricted part of the chromosome
Humans have 46 chromosomes, 22 pairs of somatic chromosomes and 1 pair of 2 sex chromosomes
Males have the Y chromosome
Females have 2 X chromosome
Problems that arise from Meiosis
Trisomy which is downsyndrome when crossing over does not occur properly
Monosomy which is turner syndrome found in females
Mendelian Trait
traits that are controlled by a single locus
Codominance traits
When 2 alleles are both equally dominant so you would see both phenotypically
ex: AB blood
Sex linked genes
traits that are controlled by genes located on the sex chromosomes
ex: red green color blindness - most females are carriers because it is recessive, while males who have the recessive gene will show for that phenotype
X linked genes
traits that are controlled by genes located on the x chromosome
ex: Hemophilia is X linked recessive
Queen had it and gave it to her son (r) and that resulted in the son having the disease and passing it down
Pleiotropy
a single gene can cause multiple phenotypes
most genes are this
PKU - inability to convert phenylalaine into tyrosine due to lack of the enzyme hydroxyalse
this also effects production of melanin, so the person will have a phenotype of light hair, skin and eyes
Polygenic traits
continuous traits that are influenced by multiple genes
EX: beak size, is influenced by multiple gene locus’ which gave it that continuous trend we saw
Behavioral Genetics
Can be inherited
Much of our behaviour is within our genes but we are able to modify and changing out behaviour
PCR
discovered and used in 1980’s
amplifies DNA in order for us to analyze it
Evolutionary Synthesis
combination of Darwin’s theory of natural selection and Mendel’s theory in inheritance
Homologous Pair
chromosomal pairs that are alike in size and position of the centromere, they carry genetic information influencing the same traits
Karyotype
Pictograph of all 23 chromosomal pairs for a human
Arranged in pairs according to size and position of the centromere
chromatin
uncoiled non-condensed DNA strands that is seen in interphase when the DNA is being used for metabolic processes and also being duplicated to go into prophase
Antigens RH found in blood
Can be + or -
makes for there to be 8 phenotypes of blood
in pregnancy is the mother is - and the baby is + there will be no issues, but during birth there is some blood transfusion which causes the mother to develop antibodies for the Rh protein
During second pregnancy this can cause an issue because the mothers immune system will start to attack the fetus that is + for Rh.
How does variation occur
mutations, genetic drift (founders effect), gene flow
Genetic Drift
random change in allele frequency to a small population over time
greater effect on small populations and mendelian traits (traits that are controlled by one gene)
Founders effect: when a small colonizing population effects the frequency of the allele
If the population that is colonizing carries most of the frequency for the allele in observation, then when it colonizes a new location, it will create that frequency to be greater, and cause a total loss of that allele in the original location
Gene flow
Movement of genes from one population to another with or without migration
Result from interbreeding
Hardy Weinberg Equation
Mathematical equation that deems that there will be no evolution if 5 things are help accountable
5 assumptions of the Hardy Weingberg Equation
1) No natural selection
2) No sexual selection (all individuals have an equal and random chance at mating)
3) no migration
4) Population in effect is infinitely large
5) Mutation does not occur
Hidden Variation
This was seen in the finches after the daphne’s draught in the late 1970s. The beak size had become dominantly large and wide due to the seeds that were available, as the smaller beak sizes were not able to eat the bigger seeds
After the draught however we saw that the beak size had gone back to the original variation from before the draught
this helped us determine that there were multiple loci in determining the beak size and when the environmental stressors were not present to influence the alleles, then all were able to be expressed giving the original continuous range of beak size.
Correlated Traits
Traits that correlate with each other and are statistically associated in a population
ex: arm length and leg length
usually seen in pleiotropic effects (1 gene causing many phenotypes, also makes us proportional)
Maladaptive Traits
Traits that do not help us survive
ex: Finches only having a large beak but not a deep beak, you need both to survive during the draught
Inheriting Behaviour
Scott P. Carroll used soapberry bugs and studied their mate guarding
found that the soapberry bugs in oklahoma would only mate guard if the ratio of males to females was either 1:1 or 2:l they would not mate guard with a ration of 1:2
Soapberry bugs found in florida however mate guarded regardless of the ratio of males to females
Behaviors can evolve if
1) they vary
2) the variation has an impact on reproductive success of the individual with that character trait
3) the behaviour must be heritable -> passed on to the next generation
Canalized behaviour trait
Will do the behaviour no matter what environmental situation the organism is in
Plastic behaviour trait
The behaviour will depend on the environment and the circumstances
usually quite costly, ie the soapberry bugs mate guard and lose their opportunity to mate with another female
humans behaviour traits are 99.9% plastic
Types of Natural Selection
1) Directional
2) Stable
3) Disruptive
4) NONE
Directional Natural selection
Driving a trait into a certain + or - direction
ex: draught caused the finches’ beak size to be directionally bigger
acts as an agent for microevolution
Stabilizing natural Selection
There is selection for the most common allele/phenotype but also some selection for both extreme phenotypes/ alleles
this will cause the population to stay the same for the traits seen over time
Disruptive Natural Selection
There is selection for both extreme phenotypes/alleles and no selection for the most common
This causes the population to see increases in both extreme traits
Found in sympatric speciation
No selection
absence of selection the population will have a variety of phenotypes/alleles
there will be no change over time
Species
organism that can recognize its members within a population, mate with them, and produce viable offspring
Genetic relatedness
determined by anatomy and morphology
genomes are related
Deme
population of organisms that have similar genes, inter-breed, and produce offspring
bound together by morphology, ecology, genome, reproduction, and behaviour
Gene pool
Genetic information available in a breeding population
Reproductive Isolation
When some mechanism prevents two populations of the same species from interbreeding and exchanging genetic material
physical ex: mountains, river, ocean
social ex in humans: religion, politics
Microevolution
Evolution within a species such as a change in allele frequency from one generation to the next
results in variation
Macroevolution
Evolution of a new species, families, and higher taxa which occurs after hundreds and thousands of years.
results in speciation
maintained through gene flow
Hyena EX
closest relative is a mongoose but they morphologically look like dogs
this is because they behave like mongoose, they chitter chatter to communicate, they make underground burrows, live in groups, the groups are lead by alpha females
How they respond to situations is more similar to a mongoose than to a dog
Biological Species concept
a species is a group of organisms that interbreed in nature and are reproductively isolated
gene flow torpedos this
Recognition Species Concept
a species is a group whose members can identify potential mates with whom might successfully interbreed based on
- morphology
- behavior
- calls
- chemical signals
Ecological Species Concept
View that emphasizes selecting in creating and maintain a species in which gene flow can occur between species
species are maintain both by behavioural and environmental pressures
This is why baboons in south africa cannot reproduce with a baboon from saudi arabia
Absence of Gene flow
ex: checkerspot butterfly
the butterfly is found in san diego and pockets of the states but the San Diego butterfly does not mate with the others
no gene flow which means no new species
Allopatric Speciation
occurs when a population is divided by some type of barrier or gene flow and different parts of the population adapt to different environments leading to new species
species that live apart and have genetic isolation
ex of allopatric speciation
Finches live on an island that have distinct regions (wet, dry) and so there is a variation of beak size on this island
Storm comes and blows some finches to a new island that only has a dry region
The beak size of the finch will only be a successful trait if it is large and deep beak size, so that is directionally selected for. There is reproductive isolation between the two island populations so there is a new species that evolves
Character Displacement
STORM #2 occurs and blows the finches that got blown the first time back to the original island, they are going to be most successful in the dry regions of the original island. they will outcompete the original finches as they can only survive there.
When competition for food, mates and other resources increases the morphologically differences between the immigrants and residents
Reinforcement
When selection acts against the viability of a hybrid offspring thus favouring speciation of the 2 types of finches
Parapatric Speciation
holds that selection alone is not sufficient to result in a new species, but needs to be combine with some other force like partial genetic isolation (reinforcement) to maintain the differences between the species
species whose ranges are continuous but not overlapping
Sympatric Speciation
ONLY THEORETICAL
different phenotypes can result in a new species over time due to population reproduction dynamics
subdeems can only reproduce with subdeems
species that coexist in the same geographical region
Richard Owen
Went against darwin and said that not all traits are adaptive
Phylogeny
arrangement of living organisms into a family tree based on shared ancestral traits
1) basis for taxonomy
2) explains why a species evolved certain characteristics and not others
3) deduces the function of morphological functions or behaviour through comparison with the traits of a different species
Cladistic Taxonomy
direct relatedness
how related organisms are due to evolutionary history
Evolutionary taxonomy
both descent (relatedness) and overall similarity in morphology and behaviour should be used to determine classification
Convergent evolution
Traits that have evolved within different species to have the similar morphology but no actual genetic relatedness
ex: eyeball - something that can sense if it is light or dark, have a depression that can be able to detect where the light is coming from, membrane for sensitive cells, a lens to focus that light and a layer to reflect that light
Variant
individual within populations having different expressions of a trait
variability
tendency for members of a population to exhibit different versions of a particular trait
variation
expression of differences for a characteristic amount members of a population
Population Genetics
science that studies how variation in gene frequency within populations are effected bu the forces that modify them over time
Heterosis
heterozygote advantage
the tendency for offspring of genetically distinct individuals to have increased vigour as they are less likely to express deleterious recessive alleles
occurs when males and females of similar genetic background mate
Neodarwinism
Huxley
1) selection is the paramount force in evolution
2) evolution entails gradual change over many generations
3) evolutions occurs within populations
mutation is the source of variation with natural selection as the mechanisms that determines whether a mutation is helpful or otherwise
Epigenetics
mechanism acting during motions (development) that modify gene expression without changing the DNA sequence
Phenotypic plasticity
potential for individuals to modify their phenotype in response to variation in external conditions in order to maintain homeostasis and function
change to survive
Transgenic epigenetic inheritance
transmission of novel phenotypic features from parent to offspring acquired without recourse to modification in DNA base sequence
environmentally mediated development can result in new phenotypes
EIS - use chromatin markers to be inherited
biogeography
geographic distribution of organisms, habitats and evolutionary history as it relates to landscape and ecology
Hybrid zone
ecological regions in which closely related species overlap in occurrences, allowing for interbreeding to produce a hybrid offspring
however these offspring are usually sterile
Reproductive Isolation Types
space: physical barriers preventing species to mate
time: activity cycles/seasons
behavior: calls and mating rituals
function: other species have different forms/sizes/ attributions from reproductive parts
gamete incompatibility: the sperm and egg will not be compatible with each other biochemically
inviability: organism is not viable, will die in development or right after birth
sterility: the offspring are not sterile and so they cannot pass their genes on
Anagensis
pattern of slow linear evolutionary change
darwinian gradualism
traits for more successful competition will become more dominant and selected for
overtime there will be a phenotypic change for adaptive traits and previous form that was selected against will disappear and be an ancestor
Cladogenesis
branching
single species may give rise to a daughter species that diverges into two distinct clades
no change in population then a sudden burst of morphological evolution
bottleneck
sudden constriction of genetic diversity appearing in a generation, commonly associated with a reduction in population size
usually with a natural disaster, political unrest, or a virulent disease
