Genetics + Evolutin Flashcards
Genotype
An organisms genetic makeup, the genetic information in genes
Telomere
Region at the end of a chromatid
Centromere
The centre that holds the 2 sister chromatids together
Long arm
Longer “arms” in relation to the centromere
Short
Shorter “arms” in relation to the centromere
What is the general structure of a nucleotide
Guanine/thymine/adenine/cytosine + sugar + phosphate group
Base T
Tyrosine
Base G
Guanine
Base C
Cytosine
Base A
Adenine
Base U
Uracil
Karyotype
A display of all the chromosomes in a cell
Homologous Chromosomes
Chromosomes with the same size and shape
Includes sex chromosomes x and y
Diploid Cell
A cell that contains two sets of chromosomes
human = 23x2= 46
Haploid Cell
The result of meiosis
A cell that has only one set of chromosomes (human = 23)
What is chromatin made from?
Compacted nucleosomes
Which are made of DNA and Proteins called histones
What are nucleosome made up from?
DNA wrapped around a histones octamer (8 histones) twice
Alleles
A variant form of a gene
Humans have two alleles because they are diploid organisms
Incomplete Dominance
When one allele isn’t fully expressed over its paired allele
Resulting in a third phenotype that is a mix of the dominant and recessive phenotypes
1:2:1
Ex: Red Flower + White Flower = Pink Flower
Complete Dominace
When one allele is completely dominant over its paired allele resulting in a 3:1 ratio
Multiple Alleles
More than 2 possible alleles Ex: Blood Type AA or Ai = A BB or Bi = B AB = AB ii = O
Codominance
Both alleles are expressed int the phenotype resulting in a third phenotype
Ex: Red Flower + White Flower = Red Flower with white spots
RR x WW = 100% RW
Occurs in blood cells
Lethal Alleles
When a combination of two alleles is lethal
Ex: Ff x Ff = FF , 2Ff, ff
But FF combo is lethal, resulting in death of offspring
Ratio is 2:1 because of the death of one dominant phenotyped offspring
Dihybrid Alleles
When 2 alleles differ in 2 different phenotypes
Ex: DdYy x DdYy = 9:3:3:1
DNA Polymerase
Adds the matching nucleotide on DNA strands
DNA replication
Semi-Conservative
One strand of the parent DNA is passed down to the next gene resulting in one new strand and one passed down
RNA Primase
Builds a primer on DNA strand so that DNA polymerase can attach to the strand
5’ to 3’
Helicase
Unwinds DNA and separates strands
Single stranded binding proteins (SSBPs)
Bind to strand to prevent the H bonds from rebinding after Helicase separates the strands
Leading strand and lagging strand?
Leading strand has DNA polymerase following behind Helicase
Lagging strand has DNA polymerase move in opposite direction of Helicase, creating Okazaki fragments
Phenotype
An organisms physical and biochemical traits
Eg: colour
Okazaki Fragments
The fragments of DNA formed on the lagging strand of the double helix
Because DNA polymerase moves in the 3’ to 5’ direction
DNA Ligase
Joins Okazaki fragments in DNA repair process
What can polypeptides be used for?
- Structural Proteins
2. Enzymes (anabolic or catabolic)
Order the stages to make proteins.
Replication of DNA Transcription Move to ribosomes Translation Protein synthesis
Promoter
Part of the DNA strand that tells RNA polymerase to start transcription
Contains the TATA box
Terminator
Stop codon tells RNA polymerase to stop transcription
mRNA
A polymer of nucleotides that contains information to be converted by translation into a polypeptide
tRNA
Transfers specific amino acid defined by their anti-codon to the large ribosomal subunit
Elongation of Translation
Large subunit has E,P,A sites (exit site, polypeptide site,acceptor site)
Subunit moves along mRNA creating a polypeptide
Termination of Translation
Stop codon
Release factor protein removes stop codon and polypeptide
Allows translation to occur again
The lactose Operon
Responsible for the regulation of lactose
Lac I
Codes for a regulator proteins
mRNA then makes an active repressor
Lac Repressor
Binds to operator and blocks the production of beta-galactosidase
When lactose is present in the cell it binds to the repressor changing its form, allowing the production of beta-galactosidase
Inducer
The inducer changes the shape of the repressor when it is present in the cell by binding to the repressor
In the lactose Operon, the inducer would be lactose
In the tryptophan Operon, the inducer is tryptophan
Tryptophan Operon
trpR codes for mRNA that makes an inactive repressor
When tryptophan is present in the cell it bind to the inactive repressor and activates it
The active repressor then blocks the operator stopping production
Ultraviolet radiation
Mainly from sunlight
Ultraviolet rays induce thymine dimers resulting in a kink in the DNA strand
Enzymes often repair the DNA which prevents skin cancer
Chemical mutagens
- Chemicals that can be incorporated into DNA because they looks similar to nucleotides but promote an incorrect base pair
- Chemicals may also add or remove a group from a nucleotide
Spontaneous Mutations
Mispairing of base during DNA replication
Nucleotides on rare occasions undergo conformational changes from one another
Types of Point mutations
Silent
Missense
Nonsense
Silent mutation
A mutation that has no effect on amino acid sequence
Missense mutation
A change in one amino acid
Nonsense mutation
Mutation that makes the stop codon occur earlier in the DNA strand, resulting in a small amino acid sequence
Insertion mutation
Inserts an extra nucleotide in the DNA strand
Causes a frame shift changing all amino acids behind the mutation
Deletion mutation
Deletes a nucleotide from the DNA strand
Cause a frame shift changing the amino acids after the mutation location
Insert/deletion of 3 nucleotides
Extra amino acid/loss of amino acid
No frame shift
Autosomal Chromosome
22 pairs of homologous chromosome
Same for male and female
Sex Chromosomes
One pair of chromosomes
Male XY
Female XX
Monosomic (Monosomy)
Genetic Disorder
Lacking a single copy of a chromosome
Non-dysjunction
The failure of homologous chromosomes or sister chromatids to separate during meiosis
Trisomics
Carrying an Extra copy of a chromosome (3)
Kingdoms
Animalia Plantae Fungi Protista Monera
Domains
Bacteria
Archaea
Eukarya
Prokaryotes
Small simple cells
Growth when resources are scarce
Very rapid reproduction when resources are plentiful
Bacteria
Most diverse domain
Usually have two bounding membranes (plasma membrane and outer membrane)
Spirochetes
Long,thin, live in low oxygen environments
Bacteria
Gram Positive Bacteria
No outer membrane
Many are soil bacteria, also many cause disease or infections
Autotrophs
An organism that manufactures it food from inorganic compounds such as CO2 and Ammonia
Proteobacteria
Very diverse
Ex: e-coli
Archaea
Some are extremophiles (live in extreme environments)
Some live at 110 degrees or in very salty environments
Many are methanogens meaning they produce methane as waste
Have no outer membrane
Membrane lipids are chemically different than bacteria and eukaryotes
Endosymbiosis
When one organism lives in another
Protist
The first eukaryotic organism
Very abundant in most ecosystems
Major predators of prokaryotes
Parasitic protests cause many diseases
Multi factorial
Possibly several genes and environmental factors
Ex: Cancer
Single Gene Disorders
Caused by a mutant gene, which may be present in only one chromosome (dominant) or both (recessive)
Transcription: Initiation
RNA polymerase binds to the promoter, the DNA strands unwind, RNA polymerase initiates RNA synthesis.
Transcription: Elongation
RNA polymerase move in 3’ to 5’ direction (synthesizing 5’ to 3’)
DNA strands reform as a double helix
Spliceosomes
Cut out introns (non coding genetic material) and leave the exons (coding genetic material) and attaches the exons in mRNA processing before translation
rRNA
Complexed with protein to form ribosomes
Translation: Initiation
A small ribosomal unit attaches to the mRNA
Small subunit recognizes a specific nucleotide sequence
An initiator tRNA binds to the start codon AUG
The large ribosomal subunit attaches to the small subunit
Requires GTP to power
Spontaneous Mutations
Nucleotides get paired with the wrong bad pair during
DNA replication
Mutagens
Interacts with DNA that cause mutations
Can also be caused by ionizing radiation, UV radiation and chemical mutagens
Chemical Mutagens
Chemicals mutagens look similar to DNA nucleotides but promote incorrect base pairing.
Repressible Operon
Anabolic pathways (when the cell needs something synthesizes)
When there is inducers present in the cell it causes the protein to bind to the Operon starting production
When there is no more inducers the protein unbinds from the operator stopping production
Inducible Operon
Used for catabolic pathways (lactose needs to broken down)
The repressor in originally bound to the Operon, once inducer is ypresent in the cell the inducer binds to the repressor and causes it to unblock the Operon
Darwin’s theory
Evolution occurs primarily because of the action of natural selection, individuals of a species belong to populations.
Homology
Similar anatomical structures but used for different functions.
Ex: forelimbs of Fox, Humans, whales
Convergent evolution
The independent evolution of similar features in different lineages
Analogous
Species share features because of convergent evolution
Vestigial Structures
Structures with little or no functions, derived from more complex structures. Remnants of features that served a function for previous ancestors
Ex: human appendix
Embryological Homologies
Organs that share a common form during development, but may have very different functions or structures once developed.
Ex: Pharyngeal pouches
Molecular Homologies
Homologies at the biochemical level.
Ex: universal genetic code
Transitional Forms
Groups with major adaptions associated with an unusual lifestyle
Ex: whales, birds
Population
Localized group of interbreeding and interacting individuals. Each species is made up of one to many populations.
Genetic Variability
Sex shuffles the variability
Individuals have unique combinations of alleles
New alleles arise by mutations in an existing allele
Very few increase fitness
Gene pool
All alleles at all gene loci in all individuals in a population
Fixed alleles
Whole population is homozygous at locus
Polymorphic Loci
2 or more alleles in a population, each present at some frequency
Microevolution
Change in the frequencies of different alleles on the gene pool over generations
Allele Frequencies Equation
P+q= 1
Hardy-Weinberg Principle Assumptions
No net mutations Random mating No natural selection Large population sizes No migration
Causes of Microevolution
Mutation Non-random mating Natural selection Genetic drift Gene flow
Genetic bottlenecks
Genetic diversity can be increased by adding individual from other populations
Captive breeding programs manage makings to preserve remaining genetic diversity
Founder effect
Some previously rare alleles end up being much more common in the new population
Polygenic inheritance
Phenotype influenced by several genes
Directional selection
One end of distribution selected against. Classic response to a changing environment
Stabilizing selection
Extreme phenotypes are selected against
Often due to different, opposing selective forces
Disruptive selection
Intermediate phenotypes are selected against
Intrasexual selection
Competition within one sex for mating opportunities
Intersexual Selection
One sex chooses a mate from the other sex
Diploidy
Hides recessive alleles from selection when they are rare
Natural selection can sometimes favour allergic variation
Balanced polymorphism
When two different version of a gene are maintained in a population of organisms because individuals with both genes are better able to survive than those with two copies of either one
Heterozygote Advantage
Individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygous
In most species individuals are heterozygous at many loci
Inter-fertility
Populations that interbreed to produce fertile offspring
Reproductive Isolation
Do not normally successfully interbreed in nature with other species
Prezygotic Barriers
Act before fertilization
Eons (Most recent to least)
Phanerozoic
Proterozoic
Archaean
Hadean
Eras( most recent to least)
Cenozoic
Mesozoic
Paleozoic
Cenozoic Periods (most recent to least)
Quaternary
Neogene
Paleogene
Mesozoic periods (most recent to least)
Cretaceous
Jurassic
Triassic
