Genetics Final

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Transposable elements

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Segments of DNA that can move from one place in the genome to another. Present in virtually every organism

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Direct Repeat

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Created when a transposable element inserts into a new chromosomal location. Staggerednicks are introduced into the target site, the TE is inserted, the gaps are filled by DNA polymerase and sealed by DNA ligase. This creates a duplication of target site that flanks the TE.

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terminal inverted repeats

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Required for transposition or movement. Each typeof elements has a characteristic repeat.

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transposase

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Protein that is encoded by the activator and provides function to the Ac/Ds complex. Ac can function on its own while Ds cannot.

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retrotransposons

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Type of transposable element that makes a copy of itself and inserts that copy elsewhere.

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retroviruses

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Single stranded RNA that are replicated by double stranded DNA intermediate. Intermediate can integrate into host chromosomal DNA, and is called a provirus. Retro viruses are bound by Long terminal repeats that are not inverted. usually contain 3 genes :gag,pol, env

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reverse transcriptase

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Transcription of RNA into DNA. controlled by pol gene in retroviruses.

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long terminal repeats

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Bind retroviruses

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homomorphic sex chromosomes

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A pair of homologous chromosomes that differ for a gene or genes that determine sexual differentiation, but the chromosomes are not cytologically distinct.

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heteromorphic sex chromosomes

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A pair of formerly homologous chromosomes that determine sex and that are cytologically distinct. Usually part or all of the chromosome becomes degenerate, thus preventing recombination between the sex chromosome at least in most regions. Mammalian Y chromosome estimated 170-310 million years old

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gynandromorph

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Different parts of a fly can be different sexes. Fly starts development with XX and one X is lost. Part of fly is XX other part is XO. Many insects and plants have an X:A balance determination.

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dosage compensation

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Mechanism that equalizes the expression of the X chromosome between sexes. Drosophila male with 1 X has same expression as XX female.

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pseudoautosomal region

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Present at the end of arms in X chromosome and in the arms of Y chromosome in humans. Recombination is very high in this region.

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testis determining factor

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On Y chromosome near pseudoautosomal region. Can participate in recombination with X leading to XX males at frequency of 1/20,000.

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Lyon hypothesis

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States that one of the two X chromosomes in female mammals becomes inactive during development and remains inactive.

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Fragile X syndrome

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Fragile site is a despiraled region near tip of the long arm of the mutant X chromosome. Most common inherited cause of retardation. rare in females and found in 1/1250 males. Males have no affected children but can have affected grandsons via daughter.

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Turner's syndrome

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XO sex xhromosomes. female but no barr body so no x inactivation. 98% abort. Survivers have short stature, small or no ovaries, no pubic hair, webbed neck

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Klinefelter's syndrome

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XXY- basically male in phenotype. female pubic hair distribution and often breast development.

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TATA box

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25-30 bp before the start of transcription. Where transcription initiation complex forms

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CAAT box

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80 bp before transcription. Influences promotor activity

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enhancer

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Control elements thatregulate transcription. Can be upstream, downstream, or within the gene. Can function in either orientation Are not restricted to specific genes. If placed near unregulated gene transcription will increase significantly

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silencer

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Bound by repressors and operate like enhancers

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zinc finger

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Second structural class of transcription factors. Proteins that contain histidine and cysteine residues at intervals. These residues bind and form the fingers. Zinc fingers bind to the major groove in DNA and bind partway around the double helix

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leucine zipper

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Third type oftranscription factor domain. leu amino acids occur every seventh position. Leu residues flanked by basic amino acids which form alpha helices in the protein. Leu residues protrude on same side of DNA and zip together with another molecule of the same arrangement.

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helix-loop-helix

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transcription factor that has three helices with two fo them separated by a loop. the HLH domain is thought to provide a surface for protein-protein interactions. The third helix is thought to be the DNA binding domain.

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Ti plasmid

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Tumor inducing plasmid. Plasmid in soil bacterium that causes tumorous growth in plants. Has been modified not to cause disease. disired gene can be inserted into plasmid, transformed into bacteria and inserted into plant cells. Cells grown in while plants using proper culture conditions.

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biolistic gun

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DNA to be introduced is used to coat very small gold particles. They are then blasted into cells and taken up by the nuclease and incorporated into chromosome.

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retroviral vector

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A retrovirus that has been modified to carry a desired gene.

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M

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Mitosis. Partof cell cycle

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G1

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Gap 1 between end of mitoses and start of DNA replication

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S

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Synthesis--when DNA is replicated

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G2

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Gap 2 between replication and the beginning of mitosis

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cyclins

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Protein that determines the progression from one step of the cell cycle to the next. Combines with cyclin dependent protein kinases and build up during part of cell cycle and modify proteins that turn on genes for functions in that part of cell

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cyclin dependent protein kinases

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Protein that determines the progression from one step of the cell cycle to the next. Combines with cyclin dependent protein kinases and build up during part of cell cycle and modify proteins that turn on genes for functions in that part of cell. Kinases add a phosphate group to other molecules or to other kinases

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oncogenes

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Dominant gene where cancer causing mutations can occur.

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tumor suppressor genes

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Recessive genes in which mutations can occur that cause cancer

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polyA tail

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often added to the 3' end of RNA

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G cap

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often added to the 5' end of RNA

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microarray

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Collection of gene sequences printed on slides for analysis of gene expression.

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EST

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Expressed sequence tags. Can be made by converting mRNA to cDNA

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BAC

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? Bacterial artificial chromosomes. Stretches of DNA that are maintained in E.coli cells. A collection of BACs are ordered by a variety of means including hybridizing them to chromosomes, restriction digests with comparison of similar sized fragments to determine overlaps, or hybridization to DNA fragments that have been genetically mapped.

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cDNA

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Copy DNA. Used in ESTs. By hybridizinf cDNAs from experimental and control conditions to microarrays of all the genes, the expression of each can be documented under various experimental conditions.

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bioinformatics

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Refers to the use of computer programs to predict the structure of genes from the genomic sequence.

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apoptosis

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Natural process of cell death that occurs during normal development. Triggered in cases where cell damage exists in order to eliminate these cells. To function proteases are released from mitochondria and dissolve cellular components. Some cancer promoting mutations are those that inhibit apoptosis

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Hox genes

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Genes that specify the location of structures like legs and eyes during embryonic development.

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totipotent

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Cells that are uncommitted and can give rise to an adult

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mosaic development

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If a cell is destroyed than an organ or group of cells will be missing in the adult. Implies that a developmental program is set down and maintained after a certain stage

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regulative development

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Differentiation of cells is strongly dependent on neighboring cells so if a cell is destroyed early in development others will fill in to form an organ.
implies existence of signals that coordinate whole fields of cells during differentiation.

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morphogenetic gradient

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The regulatory factors that determine anterior/posterior polarity

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homeotic genes

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hox genes. placeholders for anatomical structures. Mutations here can cause one structure to be replaced with another eg. antennae to legs.

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inductive interaction

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When a neighboring cell determines the differentiation of a cell

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"target knockout" mice

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Mice that have had the function of a gene removed to determine its developmental impact.