Classical Genetics and Evolution Flashcards
Define: allele
Alternative forms of an observable characteristic (For example, skin color would be the observable characteristic. Its alleles are the genotype that represents the dark or light skin colors.)
Define: genotype
Genetic makeup coding for a phenotype
Define: phenotype
Physical manifestation of the genotype (the phenotype is observable, while the genotype is the genetic makeup that codes for that observable trait)
Define: homozygous
Two identical alleles for the same trait (example: rr,RR)
Define: heterozygous
Two different alleles for the same trait (example: Rr)
What is the Law of Dominance?
The dominant allele is the one expressedin the phenotype
What is the One Gene One Polypeptide Hypothesis?
This hypothesis states that each polypeptide makes up only one gene of the many genes that code for a protein. Previously, it was believed that each polypeptide coded for an entire protein, also known as the Monocistronic Hypothesis.
What is the Monocistronic Hypothesis?
One gene is coded for by only one protein
Define: P generation
The P generation is the generation that consists of the individuals being crossed (parents)
Define: F generation
The F generation is the resulting generation from a cross
What is a progeny?
It is another name for the F generation
What is a trisomy?
Three copies of a chromosome rather than the normal two copies (example: down syndrome is caused by a trisomy of chromosome 21)
What is a monosomy?
One copy of a chromosome rather than the usual two copies
What is a monohybrid cross?
A cross, where only one trait can be studied
What is a testcross?
It is used to determine whether a phenotypicallydominant trait is homozygous or heterozygous. Both Rr and RR would produce dominant phenotypes. A testcross is used to determine whether the genotype is RR or Rr.
What is a backcross?
A cross between one individual from the F generation and one individual from the P generation
What is a punnett cross?
A method to predict the genotype of an expectedcross
What is the Law of Independent Assortment?
A law that states that genes on the same chromosome will stay together unless crossing over occur
What is a dihybrid cross?
A cross, where two traits can be studied.
Define: Incomplete Dominance
An allele is incompletely dominant if thephenotype of the heterozygous is intermediate of the homozygous phenotypes. (For example, if redwere crossed with white, the intermediate would be produced, pink.)
Define: Codominance
Codominance happens when more than one dominate allele exists and more than one of them is dominant. (For example, if red were crossed withwhite, then a striped individual would be produced since both colors are dominant.)
Define: Epistemic
A gene, which its expression is dependent onanother gene’s expression.
What is the 4 laws that Mendel came up with as the basis for genetics?
1.Genes exist in alternative forms (alleles)2. An organism has two segregated alleles from each parent for eachsomatic trait.3. Gametes cells are haploid4. Alleles are either Dominant or Recessive.
Define: Autosomes
The sex of organisms is determined by the combination of homologous sex allele i.e. XX or XY) XY= male; xx= females 22 somatic chromosomes + 2x = females 22 somatic chromosomes+ 1x +1Y = Male
How is Sickle Cell Anemia passed down?
Autosomal Codominant
How is Huntington Disease passed down?
Autosomal Dominate
How is Hemophilia passed down?
Sex linked Recessive on X (Males have no way of being a carrier)
How is Polydactylism passed down?
Autosomal Dominant
How is PKU passed down?
Recessive Autosomal gene
How is Tay Sacs passed down?
o Recessive Autosomal geneo Down Syndromeo Three copies of chromosome 21
How is Klinefelter passed down?
XXY (one extra X chromosome
How is Albinism passed down?
Autosomal Recessive
How is Tunrer Syndrome passed down?
Females with only one X rather than two
What is the Rh incompatibility?
It happens when the mother is RH- and is pregnant with a child that has RH+. This causes the mother’s blood to attack the child’s blood, thinking it is a foreign body. This usually causes more problems in the second pregnancy or later pregnancies.
Define: chromosomes
A long chain of DNA
Define: Chromatin
It is a small segment of Histones + DNA loose structures DNA during the interphase is referred to as chromatin due to its loose structure.
Define: Nucleosome
It is a long segment of chromatin. The analogy ofbeads on a string is usually used to refer tonucleosomes.
Describe the stage of interphase in mitosis
• Most cells are in the interphase stage• Cells that do not divide are always in G0 stage
Describe the G1 stage of interphase in mitosis
G1 Stage initiates interphase. The length of this stage determines the length ofthe entire cell cycle
Describe the S stage of interphase in mitosis
S Stage: the period of DNA synthesisDuring the S phase, whether during mitosis or meiosis, there is always 4n’s. During mitosis, those 4n’s divide once to become 2 2n’s cells (diploid). Each of these new cells would have the complete 46 chromosomes as the parentdoes.
Describe the G2 stage of interphase in mitosis
The cell gets ready to divide, synthesize protein, and grow.
Describe the Prophase stage of interphase in mitosis
Centrioles separate• Spindle apparatus form• Membrane dissolves• Spindle fibers appear• The two chromatids formed condense
Describe the Metaphase of interphase in mitosis
Spindle apparatus attaches chromatids
Describe the Anaphase of interphase in mitosis
The chromatid separates
Describe the Telophase of interphase in mitosis
Spindle apparatus disappears• Nuclear membrane forms• Chromosomes uncoil
Describe the Cytokinesis of interphase in mitosis
The cell divides• Cleavage furrow form
What make Plant Cells’ Division Unique?
Plants lack centrioles; the spindle apparatus is synthesized by microtubules. In addition,plants form a cell plate instead of the cleavage furrow.
What are the products of Meiosis?
Produces haploid cells/ sex cells/ gametes
Describe the Interphase stage of interphase in mitosis
2N sister-chromatids form
Describe the Prophase I stage of Meiosis
• Chromatin condenses• Spindle forms• Nucleus disappears• Each synaptic pair of homologous chromosomes contains four chromatids (tetrads).• Crossing over: The chromatids of homologous chromosomes break at corresponding points and exchange DNA.• After crossing over, sister chromatids are no longer identical due to several process including crossing-over.
Describe the Metaphase I stage of Meiosis
• Homologous pairs (tetrads) align at the equatorial plane and each pair attaches to separate spindle fibers by its kinetochore.
Describe the Anaphase I stage of Meiosis
• The homologous pairs separate and are pulled to opposite poles known as disjunction• Non disjunction is the failure of the homologous chromosomes to separate
Describe the Telophase I stage of Meiosis
Nuclear membrane forms
Describe the Second Meiotic Division in Meiosis
Meiosis in the second division is not preceded by chromosomal replication. The new cells are haploid not diploid.
What are the purine nucleotides?
Adenine and Guanine
What are the pyrimidine nucleotides?
Cytosine and Thymine
Define: Nucleotides
Nucleotides are made up of a phosphate group + a sugar + a base
What is DNA?
DNA is a double-stranded helix, according to the Watson Crick DNA Model. Phosphates make the sides of the ladder, and the bases, make the steps of the ladder. The bases are joined together with H-bonds.
What is RNA?
RNA is made of Uracil instead of Thymine It is single stranded. It is found in the nucleus as well as the cytoplasm. Ribonucleotides are the basic units of RNA.
What is M-RNA?
M-RNA transcribes the complimentary strand ofthe DNA into an M-RNA strand.
What is T-RNA?
They are found in the cytoplasm, TRNAbrings the amino acids to the ribosomes in aprocess known as translation.
What is R-RNA?
R-RNA has three binding sites to three fit each of the bases on a codon. R-RNA is the abundant type of RNA
What is DNA transcription?
DNA is copied and then it is transcribed into M-RNA. The M-RNA leaves the nucleus afterward and goes into the cytoplasm
What is DNA translation?
M-RNA is converted to Amino Acids
What are the 3 stages of Polypeptide synthesis?
InitiationElongationTermination
What codon starts the Initiations Stage of Polypeptide synthesis?
It starts at AUG (methionine)
What is the Elongation Stage of Polypeptide synthesis?
Hydrogen bonds form between the codon and the anti-codon.
What is the Termination Stage of Polypeptide synthesis?
Polyribosomes advances three nucleotide bases at a time along the M-RNAIt moves in 5’ – 3’ DirectionTerminates at UAA, UAG, or UGA Disulfide Bond is a bond between two sulfur atoms of two amino acids in the primary structure of protein. It is what determines the tertiary structure as well.
What is Translocation?
Translocation is a rearrangement between nonhomologous chromosomes. Sometimes it can lead to cancer. It is very similar to crossing over,but it happens between nonhomologous chromosomes rather than homologouschromosomes.
What is Chromosomal Abnormalities?
Chromosomal Abnormalities, which can be cancerous, can be caused be severalfactors including: Environment Mutagenic agent X-rays Ultraviolet rays Radioactivity Colchicine Mustard gas
Describe an addition mutation?
Addition Mutation: a mutation that results in the addition of a base
What is a subtraction mutation?
Subtraction Mutation: a mutation thatresults in the subtraction of a nitrogenbase
What is a point utation?
Point Mutation: a mutation that results in one amino acid base being replaced with another, causing adifferent resulting amino acid.
What is a silent mutation ?
Silent Mutation: a mutation that results in the a nitrogen base being switched with another, however, the resulting amino acid is still the same
What is a missense mutation?
Missense Mutation: a mutation that results in a different Amino Acid
What is a nonsense utation?
Nonsense Mutation: a mutation that results in the taking out an important amino acid out, such as a stop codon
What is bacterial transformation?
Foreign chromosomes fragments are incorporated into the bacterial chromosomes
What is bacterial conjugation?
Conjugation is Sexual mating in bacteria. It is the transfer of genes between bacteria that are temporary joined. Antibody resistance can be transferred from one bacterium to theother.
What is bacterial transduction?
Transduction is the process by which parts of the bacterial genes accidently become packaged into a viral genome during a viral infection.
What is bacterial recombination?
It occurs by the breaking and reattaching of adjacent regions of DNA on nonhomologous chromosomes.
Describe the shape of the bacterial plasmid
Bacteria have a circular plasmid
What are epitsomes?
Epitomes are plasmids that are capable of being interrogated into the bacterial genome
What is the direction of replication in bacteria?
Replication goes in the direction of 5’ to 3’ in bacteria
How do bacteria reproduce?
Bacteria usually reproduces through binary fission; asexual
What are the four mechanisms by which the bacterial genome vary?
Tranformation, conjugagtion, transduction and Recombination
Define: Carrying Capacity
Carrying Capacity, k, is the maximum number of organisms a population can support.
Define: Modern Synthesis
Modern Synthesis is a theory that deals with the timing of evolution. It states that evolution had to happen gradually.
Define: Gene Pool
Gene Pool is the entire collection of genes within a given population
Define: Mutation
Mutation is a change of the DNA sequence in a gene, resulting in a change of trait
Define: Genetic Drift
Genetic Drift is the concept that genetic traits, which did not exist in the original gene pool, can be introduced through mutation. It has no particular tie to environmental conditions. Thus, the random change in gene frequency is unpredictable.
Define: Gene Migration
Gene Migration is the concept that the gene pool may experience a change in frequency if a particular gene simply dies to chance fluctuations.
Define: Hardy Weinberg law of equilibrium
Hardy Weinberg law of equilibrium states that the sum of all possible alleles is one (p + q =1). The frequency of one allele is represented by P, and thefrequency of the other allele is Q. You need to know how to calculate this. We have added a video tutorial for this.
Define: Operon Hypothesis
Operon Hypothesis states that the earth is very old. It initially had no Oxygen. It had ammonia, Hydrogen, methane, and steam.
Define: Cambrian Explosion
Cambrian Explosion is a sudden appearance of a multitude of differentiated animal forms
Define: Hybridization
Hybridization is interbreeding between different species
Define: Homo Erectus
Homo Erectus is the oldest known fossil of the human genus.
Define: Australopithecus
Australopithecus has the same size brain as humans.
Define: Cro-Magnons
Cro-Magnons are Homo Sapience, which were thought to have evolved in Africa and then migrated.
Define: Altruism
Altruism is social behavior where organisms seem to place the needs of the community first before their own.
Define: Differential reproduction
Differential reproduction is a proposal, which states that those individuals within a population that are most adapted to the environment are also the mostlikely to reproduce successfully
Define: Balanced Polymorphism
Balanced Polymorphism is a selection where heterozygote individuals, for these alleles under consideration, have a higher adaptive value thanhomozygous ones. This process is known as Balanced / Stabilizing Selection, which is a process that keeps multiple alleles in the gene pool.
Define: STABILIZING SELECTION
STABILIZING SELECTION is a selection is also known as the Purifying Selection or Balancing Selection. This selection favors the heterozygoteindividuals and thus preventing the loss of any of the alleles. (In this scenario, the intermediate color snakes are most advantageous and thus produce the most offsprings.)
Define: DIRECTIONAL SELECTION
DIRECTIONAL SELECTION is a selection in which one phenotype is favored, which causes a directional change, independent of dominant or recessive allele combinations. (Either the light or the dark snakes is favored, but not both.)
Define: DISRUPTIVE SELECTION
DISRUPTIVE SELECTION is a selection in which both light and dark colors are favored over the intermediate color. This process deals withSympatric speciation.
Define: Convergent evolution
Convergent evolution: convergence occurs when a particular characteristic evolves in two unrelated populations, and thus making the two speciesconverge together. This is in contrast to divergent evolution, where two similar populations grow apart.
Define: Bottleneck effect
Bottleneck effect is a process by which a disaster kills off most of a population, leaving only very few survivals. These survivals can eventuallybecome extinct if they were unable to reproduce. However, they may enhance the population by passing the fittest genes to their offsprings.
Define: Adoptive Radiation
Adoptive Radiation is the differentiating ability of different organisms to adapt to different climates. A prime example of adoptive radiation is the bird of the Galapagos Island. They differentiated to meet the needs of their specific environment. According to this, specific species have radiated into many different species.
Define:Coextension
Coextension is the process by which one species’ extinction could cause another species’ extension. For example, if a species of snakes arefeeding on a species of rats. If the rats became extinct due to climate changes, then the snake species would become extinct because lack of food. This phenomenon is known as coextension.
