Term
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Definition
| the functional unit of inheritance |
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Term
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Definition
| alternative forms of a gene. Example: wildtype, |
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Term
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Definition
| the complement of alleles of an individual |
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Term
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Definition
the complement of observable traits of an
individual |
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Term
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Definition
all of an organism hereditary information, typically DNA
(exception: RNA viruses) |
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Term
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Definition
two nuclear divisions take place. Therefore, four cells are produced. Takes place only in diploid cells, and the cells that result (sperm and eggs) are haploid.
• In the females of humans and many plants, three cells of the meiotic tetrad abort.
• Can be summarized:
o Start: two homologs
o Replication: two dyads
o Pairing: tetrad
-genetic recombination occurs during prophase 1 of meiosis during a process called synapsis (the joining of homologous pairs of chromosomes)
-Daughter cells only receive half of the genetic material from the mother cell |
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Term
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Definition
Mitosis vs. Meiosis
• Interphase:
o Chromosome replication takes place to from sister chromatids in both mitosis and meiosis
• Anaphase:
o Centromere division occurs in mitosis in anaphase
o Centromere division doesn’t occur in meiosis until anaphase II |
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Term
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Definition
| the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes. It is one of the final phases of genetic recombination. Occurs during 4 chromatid stage of meiosis. |
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Term
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Definition
| the joining of homologous pairs of chromatids. Occurs during prophase 1 of meiosis. Start of genetic recombination. |
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Term
| How does meiosis support Mendel's law of equal segregation? |
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Definition
• Start: one homolog carries A and one carries a
• Replication: one dyad is AA and one is aa
• Pairing: tetrad is A/A/a/a
• First division products: one cell AA, the other cell aa (crossing over can mix these types of products up, but the overall ratio is not changed
• Second division products: four cells, two of type A and two of type |
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Term
| Mendel's first law of inheritance (law of equal segregation) |
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Definition
| every individual possesses two alleles for any particular gene. In each generation each parent passes one randomly selected allele to its offspring. |
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Term
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Definition
| diagrammatic representation of the arrangement of genes on chromosomes. This shows gene positions (loci) and the distances between the loci based on some kind of scale. |
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Term
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Definition
| when duplicated homologous chromosomes pair with each other (when two dyads unite as a bivalent), a cross-shaped structure called a chiasma often forms between two non-sister chromatids. Indicate that chromatids, not unduplicated chromosomes, participate in this crossover. |
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Term
| dihybrid test cross results |
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Definition
two equally frequent nonrecombinant classes totaling in excess of 50%, and two equally frequent recombinant classes totaling less than 50%. (9:3:3:1)
• *When two genes are close together on the same chromosome pair (that is, they are linked), they do not assort independently but produce a recombinant frequency of less than 50%. |
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Term
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Definition
| the loci of those genes are on the same chromosome, and hence, the alleles on any one homolog are physically joined (linked) by the DNA between them. |
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Term
| Recombinant frequency (RF) |
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Definition
can be used to infer the distance between genes and their order on a linear map (‘genetic map’)
• RF= #of all RECOMBINANT progeny (Ab + aB) / Totally # of progeny
• RF also defines map distance
• Map distances are (generally) additive
• RF of (.01) is 1% centiMorgan or map unit |
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Term
| Single nucleotide polymorphism |
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Definition
o Most used polymorphism in linkage studies
o Only one nucleotide is different from genome to genome |
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Term
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Definition
a combination of alleles at adjacent locations (loci) on a chromosome that are inherited together
o For SNPS a haplotype is a set of SNPs that are close together and usually inherited together
o The idea is to find a haplotype that is strongly linked with the disease |
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Term
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Definition
| produces a non-functional protein |
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Term
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Definition
| Polypeptides with this kind of mutation act as “spoilers.” In the heterozygote (+/M), the spoiler polypeptide binds to the wild-type polypeptide and distorts it or otherwise interferes with its function. |
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Term
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Definition
| the general case in which the phenotype of a heterozygote is intermediate between those of the two homozygotes. At the molecular level, each wild-type allele generally produce a set dose of its protein product. The number of does of a wild-type allele determines the concentration of a chemical made by the protein, such as a pigment. |
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Term
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Definition
| the expression of both alleles of a heterozygote. Example: different blood types (A and B are both dominant alleles, and when combined produce blood type AB. O is recessive). |
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Term
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Definition
an allele that is capable of causing the death of an organism
• To see if a gene is essential, a null allele is tested for lethality |
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Term
| Temperature sensitive (ts) mutations |
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Definition
| their phenotype is wild type at the permissive temperature (often room temp) but mutant at some higher restrictive temperature. |
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Term
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Definition
| any allele that affects several properties of an organism |
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Term
| One-gene—one-polypeptide hypothesis |
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Definition
| All proteins are encoded by genes. |
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Term
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Definition
the production of a wild-type phenotype when two haploid genomes bearing different recessive mutations are united in the same cell. This means the mutations are on different genes.
• When two independently derived recessive mutant alleles producing similar recessive phenotypes fail to complement, they must be alleles of the same gene. |
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Term
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Definition
In a diploid, this test is performed by intercrossing two individuals that are homozygous for different recessive mutations. The next step is to observe whether the progeny have the wild-type phenotype. If the progeny are wild type, the two recessive mutations must be in different genes because the respective wild0type alleles provide wild-type function. In this case, the two mutations are said to have complemented.
• If the progeny are not wild type, then the recessive mutations must be alleles of the same gene. Because both alleles of the gene are mutants, there is not a wild-type allele to help distinguish between two different mutant alleles of a gene. |
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Term
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Definition
| a way to test complementation in a haploid organism. When two different strains fuse, the haploid nuclei from the different strains occupy one cell, which is the heterokaryon. |
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Term
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Definition
| the situation in which a double mutant shows the phenotype of one mutation but not the other. The overriding mutation is epistatic, and the overridden one is hypostatic. |
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Term
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Definition
o Genome of most bacteria is a single molecule of double stranded DNA in the form of a closed circle. Bacteria in nature often contain extra DNA elements called plasmids. Most plasmids are also DNA circles but are much smaller than the main bacterial genome.
o Can be parasitized by viruses called bacteriophages
o Hereditary processes:
• In asexual cell division, the DNA is replicated but the partitioning of the new copies into daughter cells is accomplished by a mechanism quite different from mitosis. |
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Term
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Definition
| the contact and fusion of two different cells. A process of gene exchange in bacteria. |
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Term
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Definition
| a bacterial cell can take up a piece of DNA from the external environment and incorporate this DNA into its own chromosome. |
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Term
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Definition
| when a bacteriophage picks up a piece of DNA from one bacterial cell and injects it into another |
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Term
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Definition
| cells that will not grow unless the medium contains one or more specific cellular building blocks. |
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Term
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Definition
| no gene interaction. In analyzing double mutants, this is the null hypothesis: the two mutations are on different chromosomes. This ratio is produced because the two genes act independently at the cellular level. |
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Term
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Definition
| genes in the same pathway. Modification of the dihybrid 9:3:3:1 ratio as it combines the 3:3:1. Only possible if the double mutant has the same phenotype as the two single mutants. The identical pheontypes of the single and double mutants suggest that each mutant allele controls a different step in the same pathway. (E.g. a plant will have white petals if it is homozygous for the recessive mutant allele of either gene or both genes). |
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Term
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Definition
| suggests a type of gene interaction called epistasis. This results from genes being in the same pathway. In a simple synthetic pathway, the epistatic (overriding) mutation is carried by a gene that is farther upstream than the gene of the hypostatic (overridden) mutation. The mutant phenotype of the upstream gene takes precedence, no matter what is taking place later in the pathway. The double mutant is a member of the “4” part of the ratio, because it expresses only one of the two mutant phenotypes, and one gene must be epistatic to the other. |
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Term
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Definition
for every locus there is one allele on each chromosome, -- paternal, maternal)
-“In each generation each parent passes one randomly
selected allele to its offspring”
-(through meiosis each gamete ends up with just one
allele, when egg and sperm fuse a new complement of 2
will be formed) |
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Term
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Definition
| the physical carrier of genetic information, a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences |
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Term
| chromatin/euchromatin/heterochromatin |
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Definition
chromatin: complex of DNA/histones
euchromatin: corresponds to loosely packed and "active" DNA.
heterochromatin: more densely packed inactive and/or repressed DNA |
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Term
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Definition
| basic unit of DNA packaging (~147bp of DNA, spooled twice around a histon octamer, containing 2 of each histone H2A, H2B, H3, and H4). |
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Term
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Definition
an individual is missing either a chromosome from a pair (monosomy) or has more than two chromosomes of a pair (trisomy, polysomy)
-caused by nondisjunctions during meiosis |
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Term
| Examples of alterations in the structure of chromosomes |
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Definition
Deletions: a piece of the chromosome is missing (deleted)
o Duplications: a piece of the chromosome is duplicated
o Inversions: a piece is inverted - (aBCDe becomes aDCBe) |
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Term
| mutations in X-linked genes |
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Definition
| (genes located on the X) are always DOMINANT in the male, even if recessive in females |
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Term
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Definition
Trait is more common in males: females get the trait ONLY if they inherit it from BOTH parents (pure recessive)
• All progeny of affected males is normal, but ALL female
progeny will be carriers
• No male-to-male transmission (male progeny always only
gets Y from dad, never X) |
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Term
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Definition
Trait is only present in males, and is transmitted from dad to son as dominant
• Very rare |
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