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What are characters in genetics?
Different heritable features, such as flower color
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What are traits in genetics?
Character variants, such as purple or white flower color
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What are the advantages of using the pea plants in genetic study?
- Characters and character traits
- Mating easily controlled
- Stamens and carpel
- Cross pollination (fertilization between different plants) involves dusting one plant with the pollen of another
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What are the sperm and egg producing organs in plants?
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True-breeding
Plants that produce offspring of the same variety when they self-pollinate
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Hybridization
Mating 2 contrasting, true-breeding varieties
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True breeding parents
P generation
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F1 generation
The offspring of the true breeding parents
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F2 generation
The product of when the F1 generation self-pollinates or cross pollinates with another F1 hybrid
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What was Mendel's term for genes?
Heritable factors
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What were some of Mendel's important discoveries?
- Factors exist in versions (alleles)
- Alleles segregate/separate (law of segregation)
- Independent assortment
- Particulate inheritance
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What 3 mechanisms contribute to genetic variation?
- Independent assortment of chromosomes
- Crossing over
- Random fertilization
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What factors should an experimental organism have?
- Easy to culture (small size; minimal nutrient requirements)
- Quick generation time
- Simple genetics
- Mutant form apparent
- Economic importance
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Character state
Discreet expression or form, 1 among several, for a given character.
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Monohybrid
Individuals that are heterozygous for one character
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Dihybrids
Heterozygous for both traits
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Law of Segregation
the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes
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Law of Independent Assortment
- •each pair of alleles segregates
- independently of each other pair of alleles during gamete formation
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Inheritance of characters by a single gene may deviate from simple Mendelian patterns in certain situations such as
- When alleles are not completely dominant or recessive
- More than one allele
- When a gene produces multiple phenotypes
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Complete dominance
occurs when phenotypes of the heterozygote and dominant homozygote are identical
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Incomplete dominance
the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties
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Codominance
two dominant alleles affect the phenotype in separate, distinguishable ways
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Polygenic inheritance
an additive effect of two or more genes on a single phenotype
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Chromosome Theory of Inheritance
–Mendelian genes have specific loci (positions) on chromosomes
–Chromosomes undergo segregation and independent assortment
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Wild type phenotype
the most commonly occurring phenotype in nature
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How do you create an F2 generation?
Cross the F1 generation with itself
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Types of linkages
- Two traits on same chromosome
- sex-linkage: a trait that is linked on a sex chromosome
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What is the SRY gene's function?
On Y chromosomes, code for male anatomical parts
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For a recessive X-linked trait to be expressed...
- Female needs two copies of the alleles (heterozygous)
- Male needs one copy of the alleles (hemizygous)
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Parental types
offspring with same phenotypical traits as the parents
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Recombinant
Offspring with phenotypical traits different from parents
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Semi-conservative
Some of the DNA that is replicated is the old strand and some is new
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Topoisomerase
Enzyme that prevents supercoiling by cutting DNA and then reconnecting it
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Single stranded binding proteins (SSBP)
Protects DNA while in single stranded state
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Okazaki fragments
Each fragment on a lagging strand
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Coding DNA
Used to make proteins
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Origins of replication
Where the two DNA strands are separated, opening a replication bubble
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RNA primase
An enzyme that starts an RNA chain from scratch and adds RNA nucleotides one at a time using the parental DNA template
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DNA ligase
Joins together Okazaki fragments
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Transcription unit
Stretch of DNA that is transcribed
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Three stages of transcription
- Initiation
- Elongation
- Termination
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Anticodon
Carried by tRNA. Base pairs with a complementary codon on mRNA
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Replication fork
Y shaped region where new DNA strands are elongating
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DNA polymerase
synthesizes a leading strand continuously, moving toward the replication fork
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RNA primer
Short nucleotide strand where the 3' end serves as the starting point for a new DNA strand
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Gene expression
The process by which DNA directs protein synthesis in transcription and translation
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Transcription
The synthesis of RNA under the direction of DNA
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Translation
Synthesis of polypeptide using information in the mRNA
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Site of translation
Ribosome
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Primary transcript
The initial RNA transcript from any gene prior to processing
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Central dogma
- Concept that cells are governed by a cellular chain of command:
- DNA -> RNA -> protein
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Template strand
One of the two DNA strands that provides a template for ordering the sequence of complementary nucleotides in a RNA transcript
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RNA polymerase
Pries the DNA strands apart and hooks together the RNA nucleotides
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Promoter
The DNA sequence where the RNA polymerase attaches
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Terminator
Sequence signaling the end of transcription
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RNA processing
When enzymes in the eukaryotic nucleus modify pre-mRNA before the genetic messages are dispatched to the cytoplasm
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During RNA processing, has is pre-mRNA modified?
The 5' end gets 5' cap and the 3' end gets a poly-A tail
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What are the functions of the 5' cap and the poly-A tail?
- Facilitate the export of mRNA
- Protect mRNA from hydrolytic enzymes
- Help ribosomes attach to 5' end
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Introns
Non-coding sequences in RNA
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Exons
Regions that are eventually expressed and translated into amino acid sequences
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RNA splicing
Removes introns and joins exons
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Spliceosomes
Consist of a variety of proteins and several small ribonucleoproteins (snRNPs) that recognize splice sites
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What are the three binding sites for tRNA on a ribosome and what are their functions?
- P site: holds the tRNA that carries the growing polypeptide chain
- A site: holds the tRNA that carries the next amino acid to be added to the chain
- E site: exit site where discharged tRNAs leave the ribosome
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Nucleotide pair substitution
Replaces one nucleotide and its partner with another pair of nucleotides
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Silent mutations
Have no effect on the amino acid produced by a codon because of redundancy in the genetic code
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Missense mutations
Still code for an amino acid, but not the correct amino acide
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Nonsense mutations
Change an amino acid codon into a stop codon nearly always leading to a nonfunctional protein
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Insertion or deletion of nucleotides may alter the reading frame, producing a...
Frameshift mutation
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Mutagens
Physical or chemical agents that can cause mutations
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When did Darwin publish Origin of Species?
1859
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Scala natura
Scale on which organisms were arranged by Aristotle when they were thought to be static
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Catastrophism
Organisms are molded by catastrophe
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Uniformitarianism
Mechanisms of change are constant over time, such as weathering/erosion, sedimentation, subsidence/uplift
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Homology
Similarity coming from common ancestry
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Homologous structures
Anatomical resemblances that represent variations on a structural theme present in a common ancestor
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Vestigial structures
Remnants of features that served important functions in the organism's ancestors
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Biogeography
Geographic distribution of species
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Endemic species
Species that are not found anywhere else in the world
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Convergent evolution
Evolution of similar or analogous features in distantly related groups
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Logistic/Sigmoid growth
When a species does not take the carrying capacity of its habitat into consideration so therefore produces too many offspring which then die rapidly, creating a sharp incline and decline in population
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Intrinsic rate of growth
R max
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Types of fossils
- Direct (bones, tissue)
- Indirect (footprints, dung, teeth marks)
- Micro and macro (unicellular organisms)
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Aspects of Natural Selection
- Variation in a population
- Phenotype/physical differences associated with differences in reproductive success (fitness)
- Populations always grow beyond the environment's capacity to support them
- Competition ensues
- Differential reproduction and survival of so-called "favored" variation
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