Chapter 4 Flashcards
Origins of Life
How the first living organism came into being
Phylogenies
Genetic lineages (the evolution of genes in a species/group)
Phylogenetic tree
A family tree of all living organisms based on genetic relationships
How many years ago did the origin of life occur?
3.8 billion years ago
Universal ancestor
The first living organism where all living things are descended (where all organisms came from one single ancestor)
What do we know about the origins of life?
That a single-celled organism made copies of itself and led to the creation of many other species
Darwin
Founded natural selection
Gregor Mendel
Founded particulate inheritance (the idea that physical traits can be passed on to their offspring through genes)
Why did Medel’s and Darwin’s ideas fall out of favor?
Their ideas fell out of favor because both of their theories did not explain evolution entirely (both of their theories did not explain the entire picture)
Lamarckian inheritance
The idea that physical traits acquired over one’s lifetime can be passed on to their offspring (cutting hair or an injury)
What don’t we know about evolution?
We don’t know exactly how the first being came to be
Pangenesis
Darwin combined Lamarck’s theory and claimed that the physical traits acquired over one’s lifetime can be passed on through particles sent by all cells of the human body. These particles congregate in the reproductive system. (Incorrect theory)
How was Lamarck’s theory debunked?
It was debunked through an experiment. Weismann cut off mouse tails to see if the cut-off tails would be passed on. However, all of the baby mice were born with intact tails, so Lamarck’s theory was incorrect.
Hugo Marie de Wries
Dutch botanists who created the concept of genes and mutation
Carl Correns
German botanist who discovered the principles of heredity (this was achieved simultaneously but separately from Hugo de Vries)
Mutationists
Group of scientists who believed variation is caused by mutations in distinct inherited cells
Biometricians
A group of scientists believed that individual mutations could not account for a continuous spectrum of variation (the idea that mutations could cause a wide spectrum of variation like height or weight)
Does evolution take place in populations or individuals?
Populations
Population
Group of individuals who are of the same species who are geographically near each other which allows them to reproduce offspring
Species
Organisms of the same group can reproduce with each other because they are biologically and behaviorally compatible to produce with each other
Viable Offpsring
Offspring that are healthy enough to survive to adulthood
William Castle and John Phillips
They discovered that they could breed rats with a wide variety of colors
Thomas Hunt
Conducted studies on fruit flies where he discovered how chromosomes and genes play a role in heredity.
What did Thomas Hunt discover?
Most mutations increased variations within populations rather than creating new species
R.A. Fisher and John
Burdon
Developed and tested mathematical models for evolutionary change that created the basis for studying population genetics
Sewall Wright and Theodosius
Performed studies where they discovered that chromosomes are the carriers of genes
Edmund Brisco
conducted studies on wild butterflies that confirmed that there are multiple forms of a trait
Polymorphisms
Multiple forms of a trait
Julian Huxley
Published a book on the summary of evolution called the modern synthesis
Modern Synthesis
Unified theory of evolution
Fertile Offspring
Offspring who can have offspring of their own
Subspecies
Species that are physically different and geographically isolated from each other but can interbreed with other species if they choose to do so
Why can’t hybrids reproduce?
Because they have a mismatched set of chromosomes that doesn’t allow for the reproduction of offspring
Genes
The basic unit of information that encodes proteins needed to grow and function as a living organism
Alleles
Variant of a trait
Genotype
The genes that an individual inherits
Phenotype
Physical traits that can be observed that are influenced by one’s genes
Homozygous Genotype
Carrying two of the same alleles
Heterozygous Genotype
Carrying two different alleles of a trait
If a population has subspecies, what can you conclude about the history of that population?
That a species become geographically separated that they developed physical traits separate from each other but can still reproduce with each other
How is it possible for tigers and lions as well as horses and donkeys to mate successfully yet have offspring that are infertile?
Their hybrids have unequal chromosomes that don’t allow for reproduction
Evolution
Change in allele frequencies in a population over time
Allele Frequencies
The ratio or percentage of allele frequencies in comparison to other alleles in a population
How common an allele frequency is within a population
Dominant vs recessive alleles
Genotype Frequencies
The number of individuals who have a given genotype in a population
How frequently does that genotype show up in a population
What are the forces of evolution?
The mechanisms that account for genotype variation: mutation, genetic drift, gene flow, and natural selection
How can we be fairly certain that these four processes of genotype variation give us an accurate sense of how evolution happens?
Because they have been retested over and over again in modern synthesis
Mutation
Copying error that leads to a change in genetic code that leads to gene variation
Deleterious mutations
Mutations that cause negative effects such as cancer or heritable diseases
Beneficial mutations
Changes in the DNA that provided some sort of advantage to a given population at a particular moment in time
UV cross-linking
Interaction with UV light
A type of mutation in which adjacent thymine bases bind to one another in the presence of UV light
DNA repair mechanisms
enzymes that patrol and repair DNA in living cells, while other mutations may cause a new freckle or mole or, perhaps, unusual hair
to grow
Autosomal recessive
The pattern of inheritance characteristic of genetic disorders
Xeroderma pigmentosum
A genetic disorder that decreases the ability to repair DNA damage caused by UV light (effects include sunburn, skin pigmentation, freckling etc)
Somatic
Cells of our organs and other body tissues
Which mutations in cells are passed on to offspring?
Only mutations in gametes are passed on
Gametes
reproductive cells
Spontaneous Mutation
A random mutation that occurs in a family lineage
Inherited Mutation
A random mutation that occurred in a family lineage that has passed on its offspring
Point mutation
A point mutation is a type of mutation in DNA or RNA, the cell’s genetic material, in which one single nucleotide base is added, deleted, or changed.
The DNA base is replaced with another such as replacing thymine with adenine. This leads to a change in RNA.
Codons
Each gene is translated through three-letter words called codons
Cystosine methylation
A very common reason as to why point mutation occurs (a change in the DNA’s nucleotide which leads to a different protein). A chemical change. where a cystosine nucleotide is changed to a thymine.
What is the most common cause of autosomal dominant disorder?
During DNA coding, cystosine is accidentally replaced with thymine.
Synonymous Mutations
A mutation that occurs but does not change the protein. Even though there is a letter chance, the DNA is still read the same which produces the same protein.
Non-synonymous Mutation
Mutations that do cause a change in a protein
How many types of non-synonymous mutations are there? What are they?
Three: missense, nonsense, and splice site mutations.
Missense Mutation
One of the DNA pairs is changed for example A for C. As a result, the DNA now codes for a different amino acid. This change in the amino acid can be neutral, positive, or negative.
Nonsense Mutations
Creates a single change to a DNA base pair. However, it encodes stop codons prematurely into the protein which will stop protein synthesis prematurely. This can have a much greater effect in comparison to missense mutations because it stops protein production prematurely. This can have a major or minor impact.
Intron
DNA that makes up a gene (a single section of DNA). Used in pre-rna (not final rna). Sections of mRNA that do not code for a protein. Removed from the pre-RNA.
Splice site mutation
A mutation where the genetic code is changed where the process of removing intron sequences from the mRNA is disrupted. The process is affected where an intron can still remain when it should be removed and an exon be removed when it should have remained in the mRNA.
What other type of class of mutations exist?
Insertions and deletions (indels).
What are insertions and deletions?
Insertion-adding one or more letters
Deletion-deleting one or more letters
Frameshift Mutations
When a nucleotide has been added or deleted, this changes how RNA reads the DNA (which is read in groups of 3), which changes what protein is being produced
Transposable elements
Jumping genes that move from one location on the genome to another. A section will be cut out of a sequence and reinserted elsewhere.
Class 2 transposons.
Retrotransposons
DNA that is copied into the RNA and then that section that was copied into the RNA is recopied back into the DNA in another location
Class 1 transposons.
Why is a frameshift mutation very serious for the organism?
They are very serious because they cause all the codons after the mutation to be misread. This can cause extensive changes to the protein which can cause loss of function and new interactions between the protein and other parts of the cell.
How might transposons be responsible for genetic variation?
When transposons become very active, they accelerate the mutation rate, which increases genetic variation
What are the three genetic mutations that occur on the chromosomal level?
Crossover events, nondisjunction events, and translocation
Crossover Events
It’s when DNA is swapped and split into two cells during meiosis (these don’t create new alleles but create different combination of alleles) that can be passed down to future generations
Nondisjuntion Events
This is when chromosomes fail to split during meiosis or mitosis which can lead to daugher cells having a larger number of chromosomes than necessary. Also, this leaves the other daughter cell with no chrosomosomes which is fatal to the embroyo.
Trisomies
A genetic disorder where a person has three chromosomes instead of two
Monosomies
Inheritance of X chromosome from one parent but no sex chromosome from the other.
Leaves one sterile.
Chromosomal translocations
Transfers of DNA between non-honologous chromosomes (Chrosomes that aren’t the same). Exchanges of DNA can be balanced or unbalanced.
Balanced translocations
Genes are swapped but no genetic information is lost
Unbalanced translation
Unequal exchange of genetic material which leads to duplication or loss of genes
Derivative chromosomes
Structurally rearragned chromosome featuring two or more chromosomes
What is the problem with translocation?
It leads to cancer and infertility
What happens to babies who only inherit a sex chromosome from one parent?
It will die off
Neurofibromatosis Type 1
Common genetic disorder that causes skin growths
Autosomal Dominant
Everyone that is born with a mutation in a gene (whether that’s inherited or spontaenous) has a 50:50 chance of passing it on to their offspring
Exons
Parts of the gene that remain in the mature mRNA after RNA splicing
Benign
non-cancerous tumor
Cutaneous neurofibromas
Overgrowth of nerve tissue that look like bumps on the skin
Plexiform neurofibromas
looks like the skin is melting
café-au-lait spots
flat, brown birthmark-like spots on the skin
Genetic Drift
random changes in allele frequences from one generation to the next
Why is “genetic drift” not a good name for this process?
Refers to genes drifting rather than alleles which is what is actually happening
When does genetic drift occur?
It occurs based on generation (it differs generation to generation)
What makes some alleles more common than others?
It’s a completely random process
asexual reproduction
Single parent produces offspring (offspring has same inhertied genes and traits as parent)
sexual reproduction
Two parents produce offspring (offspring is a mixture of genes from both parents)
Population Bottleneck
A random event like a natural disasater kills of many individuals in a population. This decreases the amount of alleles in a population
Cretaceous–Paleogene extinction
A prehistoric disaster that led tp the extinction of dinosaurs. Occured 66 million years ago, an asteriod hit the Gulf of Mexico and wiped out many dinosaurs
Antibiotics
Medicines used to treat antibacterial infections
Founder effects
members of a population leave the original group (they don’t interbreed with the original group). Can cause rare alleles to become very common
guevedoces
Created through the founder effect. Male organs in females at age 12
5-alpha reductase deficiency
Doesn’t allow male organs to form properly
Ellis-van Creveld syndrome
an autosomal recessive disorder is characterized by short stature dwarfism), polydactyly [the development of more than five digits fingers or toes) on the hands or feet], abnormal tooth development, and heart defects
Gene flow
the movement of alleles from one population to another
admixture
Among humans, gene flow is often described as admixture
Why is it true that there are no distinct human genetic populations?
All modern humans are members of the same fully breeding-compatible species
Hybridization
Gene flow between otherwise isolated non-human populations
Africanized Honey Bees
A genetically modified version of honey bees that are extremely aggressive
Harlequin ladybeetle
“natural” form of pest control that were introduced to north america from east asia as pest control
Natural selection
when certain phenotypes are considered an advantage or disadvantage in survival and/or reproductive success
peppered moth
A moth that became darker over time to compensate for the soot-covered trees but later became a problem because the moths would stand out when the trees became white again after the industrial revolution
How many types of natural selection are there?
directional, balancing/stabilizing, or disruptive/diversifying
Balancing selection
a balance of two extremes of an allele. A medium size baby
Disruptive selection
When extremes of a trait are an advantage. The two extremes of a trait can become two separate populations.
Directional selection
The environment preferring one allele over another
Sickle cell anemia
autosomal recessive genetic disorder that affects millions of people worldwide. Inhibits blood flow in the body. Creates physical pain.
malaria
an infection of the blood by a Plasmodium parasite
Sexual selection
natural selection in which the selective pressure specifically affects reproductive success. Can make it hard to survive as a sexual trait may not be conducive to the environment. Peacock feathers make peacocks more susceptible to prey.
Dictyostelium discoideum
species of slime mold
Hardy-Weinberg Equilibrium
a mathematical formula that allows the estimation of the number and distribution of dominant and recessive alleles in a
population. Calculates the estimation of allele frequencies that are changing and, if so, how quickly over time, and in favor of which allele?
Once change has been noted in a population, what is the next step?
we need to consider which evolutionary processes might be
the cause of the change.
Non-Random Mating
mate choice within a population follows a nonrandom pattern.
Positive assortative mating
tendency for individuals to mate with others who
share similar phenotypes
Negative assortative mating
individuals tend to select mates with qualities different from their
own
artificial selection
humans who decide which
pairs will mate to increase the chances of offspring having certain desirable traits
Microevolution
changes in allele frequencies within breeding populations, that is, within single species
Macroevolution
involves changes that result in the emergence of new species
speciation
When a single population divides into two or more separate species
Allopatric speciation
long-term isolation
physical separation) of subgroups of the population. Something occurs in a population that stops individuals from mating. The environments that are created affect the two separated species that they become biologically different and can’t procreate even if that barrier is removed.
Sympatric speciation
population splits into two or more separate species while remaining located
together without a physical barrier. Mutation stops individuals from reproducing
Adaptive radiation
subgroups of a single species rapidly diversify and adapt to fill a variety of ecological niches
ecological niche
constraints and resources that is available in an environmental setting
