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Heredity and Evolution

Heredity and Evolution: Molecules and Genetics

Terms

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Lagging Strand
The discontinuously synthesized strand of DNA that elongates in a direction away from the replication fork through the formation of a series of Okazaki fragments. DNA polymerase can only add nucleotides to the 3' end of the growing DNA strand.
Sympatric speciation
The evolution of new species that occurs within a population of that species; this kind of speciation occurs as a result of mutation or selective breeding in a population.
Natural Selection
Darwin's theory that differential success in the reproduction of organisms with different phenotypes results from the interactions of these individuals with their environments. Evolution occurs because those better suited to an environment will survive to produce more offspring and pass along their genes to the next generation.
Genotype
The genetic make-up of an organism; the entire set of alleles that an organism possesses. Genotype determines phenotype in organisms.
Punctuated Equilibrium
One theory of evolution advocating that evolutionary change occurs in quick spurts of rapid change followed by longer periods of stasis during which almost no evolution takes place.
transfer RNA (tRNA)
An RNA molecule that acts as an interpreter between mRNA and proteins by picking up specific amino acids and pairing them with compatible codons on mRNA during translation.
Retrovirus
Any RNA virus that reproduces by first transcribing its RNA into DNA and then inserting the DNA into the chromosome of a host cell, where it is replicated along with the host chromosome.
Polymerase Chain Reaction
A lab technique for quickly making multiple copies of a DNA segment in vitro by incubating the fragment with a primer, nucleotides, and DNA polymerase.
Gel Electrophoresis
A lab technique used to separate nucleic acids or proteins on the basis of their size and electric charge by measuring the distance that they travel through a gel matrix once charge is applied across the matrix. Small particles travel more quickly, and therefore farther, than larger particles.
Restiction Enzyme
A bacterial enzyme that recognizes and cuts DNA at specific sites known as restriction sites. Restriction enzymes are used in the lab to create recombinant DNA which is DNA that contains genes from two sources.
Restriction Site
The specific sequence of DNA where a particular restriction enzyme will recognize and cut; each type of restriction enzyme cuts at a distinct restriction site.
The set of observable and unobservable traits if an organism is known as what?
The phenotype of an organism is the set of all of the physical and physiological traits of an organism.
What type of speciation occurs when populations have geographically separate ranges?
Allopatric speciation: This causes an interruption of gene flow between members of the two now distinct populations and recults in the evolution of new species.
Nondisjunction
When a pair of chromosomes fails to separate properly during gamete formation; an accident in mitosis or meiosis(in meiosis it is the failure of sister chromatids to separate properly).
Vestigal organs
Structures that represent historical remnants of structures that had important functions in ancestors but no longer are of any use. Examples: appendix
What cell structure is the direct result of X chromosome inactivation?
A Barr body. This is a dense mass inside the nuclear envelope of all female mammalian cells, which is formed by the inactivation during embryonic development of one of the two X chromosomes received from the parents.
Anticodon
A triplet of bases that occurs at one end of a tRNA molecule; this specific sequence recognizes the complementary codon on an mRNA molecule in the A site of the ribosomal complex during the process of translation in the cell cytosol.
Primer
An RNA chain that is bound to a complementary sequence on the DNA template; DNA nucleotides are added to the primer at the start of DNA synthesis and are necessary for the initiation of synthesis.
Mendel's First Law
The principle stating that the two cariants of a genetic trait(alleles) will segregate during gamete formation.
Sex Chromosome
A chromosome involved in determining the sex of an individual. Humans have two sex chromosomes and forty-four autosomes. Human females have two X chromosomes, whereas males have one X chromosomes and one Y.
Pleiotropy
The phenomenon in which a single gene has multiple effects on the phenotype of an organism.
Species
A group of organisms defined by their ability to interbreed with each other and produce viable offspring.
What is an individual who has the genotype AABB said to be for both alleles?
Homozygous organisms have two identical alleles for a given trait, whether the alleles are dominant or recessive.
Hybrid
A genetic mixture of two parents; the offspring of two genetically different parents. Hybrids are usually heterozygous for a variety of genes.
Incomplete dominance
In this type of inheritance, F1 hybrids have an appearance that is intermediate betweem the phenotypes(appearances) of the two parents.
Gradualism
A theory of evolution on Earth stating that all evolutionary change has been the result of the accumulation of small but continuous changes and processes. This theory was replaced by the theory of punctuated equilibrium.
Repressor
A protein(enzyme) that represses the transcription of a gene by binding to the strand of DNA at the promoter.
Mutagen
An agent(either chemical or physical) that causes an alteration in the DNA sequence.
What is the term used to describe the one-way transfer of DNA between two bacteria?
Conjugation is the one-way transfer of genetic material (DNA) between two bacterial cells that are joined temporarily.
What term is used to describe a circular DNA molecule found in prokaryotes?
A circular DNA molecule found in prokaryotes is known as a plasmid; plasmids carry accessory genes that are separate from those of the bacterial chromosome and are also found in some eukaryotic cells.
Histone
A protein molecule that has a slightly positive charge and binds to the negatively charged DNA molecule; together histones and DNA form chromatin.
Operon
In bacteria and phages(bacterial viruses), a unit if genetic function that consistes of clusters of genes
Speciation
The emergence of new species through evolution.
Origin of Replication
Site where the replication of the DNA molecule begins in DNA synthesis. Also the site where DNA polymerase and the other proteins associated with DNA synthesis initially bind.
Ribonucleic Acid (RNA)
One type of nucleic acid polymer. The sugar in RNA nucleotides is ribose. RNA nucleotides have the bases adenine, cytosine, guanine, and uracil.
Prion
A protein that is infectious and thought to be misfolded. Prions are thought to increase in number by converting similar proteins into misfolded forms and to be the cause of certain infectious diseases such as mad cow diseases.
Linked Genes
Genes on the same chromosome. The recombination frequency of linked genes can be used to calculate the position of genes along a chromosome since there is a direct correlation between the frequency with which linked genes cross over and the distance they are from one another on the chromosome.
Gamete
A haploid sex cell (an egg or a sperm); male and female gametes join during fertilization to produce a diploid zygote. Gametes are produced by germ cells.
Autosome
Any chromosome that is not one of the sex chromosomes (X or Y). Humans have 44 autosomes in 22 homologous pairs. The 2 sex chromosomes constitute the 23rd pair of chromosomes.
Phage
A virus that infects bacteria; also known as a bacteriophage.
Ribosome
A cell organelle that is made in the nucleolus of the nucleus and functions as the site of protein synthesis in the cytoplasm. Ribosomes are made up of rRNA and associated proteins.
Inclusive fitness
An individual's fitness, including both the genes that the individual passes on to the next generation and the shared genes that the individual helps to pass along through altruism, for example.
Intron
The noncoding regions and sequences of a eukaryotic genome, interrupted by coding regions known as exons.
Polygenic inheritance
The phenomenon in which two or more gene loci have an effect on one certain character of the phenotype.
Homologous chromosomes
Chromosomes that are paired; have the same length, centromere position, and staining pattern; and possess genes that code for the same characteristics at the same loci. One of the homologous chromosomes of a pair was inherited from the mother, whereas the other was inherited from the father.
Viviparous
Refers to animals that give birth to live young, which are born after being nourished in the uterus by blood from the placenta.
The direct result of transcription is the production of what molecule?
mRNA is produced during transcription. mRNA is a type of RNA that attaches to ribosomes in the cytoplasm of the cell and specifies the primary structure(the sequence of amino acids) of new proteins. mRNA is synthesized from DNA.
Okazaki Fragments
The short segments of DNA that are synthesized on the lagging strand during DNA synthesis; these are later fused by DNA ligase.
Promoter
A specific sequence of nucleotides in DNA that binds to RNA polymerase and indicates the starting point of mRNA trnascription.
Yeast
A unicellular fungus that lives in moist habitats and reproduces primarily by simple cell division or by budding off the parent cell.
Gene Flow
The loss or gain of alleles in a population resulting from migration into or out of the population of individuals that are capable of breeding.
Down Syndrome is the result of what chromosomal condition?
Trisomy of chromosome 21. The nondisjunction of chromosomes during meiosis produces gametes with extra copies of chromosomes. In trisomy, the organism has three chromosomes instead of the normal two.
Telomere
The end of a eukaryotic chromosome; consists of tandemly repeated DNA sequences and protects the end of the chromosomes from being degraded through multiple rounds of replication.
Leading Strand
The continuously synthesized strand of DNA in DNA replication, synthesized in the 5' to 3' direction by DNA polymerase. This strand elongates in a direction toward the replication fork.
What term describes the lining up of homologous chromosomes during prophase I of meiosis?
The lining up and pairing of homologous chromosomes during prophase I of meiosis is known as SYNAPSIS.

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