Genetics Lecture 17
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39 terms
Terms | Definitions |
|---|---|
 What is dideoxy termination used for? | DNA sequencing |
| How does dideoxy termination work? | A 3' OH on the nucleotide is required for chain elongation. A dideoxyribonucleotide will lack the 3' (and 2') OH groups, termination DNA elongation at this point. |
| Describe the process of sequencing a gene by dideoxy termination. | DNA strand is mixed with: -labeled primer -DNA polymerase -4 dNTPs (normal) -ddATP (or ddTTP, etc.) This will result in several shorted strands, each truncated at the point of addition of the ddNTP. Each mixture is then runon a lane of acrylamide gel. Shortest sequence (travels furthest in gel) will be the 5' end of the template (the 3' of the original DNA strand added to the mixture) |
| Why was sequencing the whole genome very difficult? | -sequencing reaction would produce only 500-800 bp at a time -each sequencing reaction required a primer, so the beginning of a sequence would have to be known to determine the rest -the genome is full of repetitive sequences (transposons) so it's easy to get lost |
| What are two alternative approaches to sequencing the genome by dideoxy termination? | -hierarchical shotgun -whole genome shotgun |
| Which sequencing method was preferred by the Human Genome Project? | Hierarchical Shotgun |
| Which sequencing method was preferred by Celera Genomics? | whole genome shotgun |
| Genetic map: Recombination Technology: _______ Units: _______ | Genetic map: Recombination Technology: meiotic recombination Units: cM |
| Genetic map: ________ Technology: meiotic recombination Units: _________ | Genetic map: Recombination Technology: meiotic recombination Units: cM |
| Genetic map: Cytogenetic map Technology: _________ Units:____ | Genetic map: Cytogenetic map Technology: chromosome staining and FISH Units: μm |
| Genetic map: ___________ Technology: chromosome staining and FISH Units: ___ | Genetic map: Cytogenetic map Technology: chromosome staining and FISH Units: μm |
| Genetic map: Physical map Technology: _________ Units: ______ | Genetic map: Physical map Technology: restriction mapping Units: kb |
| Genetic map: ________ Technology: restriction mapping Units: ___ | Genetic map: Physical map Technology: restriction mapping Units: kb |
| Genetic map: Sequence map Technology: ___________ Units: __ | Genetic map: Sequence map Technology: Sanger cycle sequencing Units: bp |
| Genetic map: ___________ Technology: Sanger cycle sequencing Units: ____ | Genetic map: Sequence map Technology: Sanger cycle sequencing Units: bp |
| The first draft of the human genome was published in _____ | 2001 |
| Euchromatin: __________________ | a chromosomal region that is lightly packed chromatin and contains transcribed genes |
| Heterochromatin: _________ | tightly packed chromatin for the most part genetically inert (centromeres, telomeres, also some genes). characterized by low gene density ans the presence of highly repetitive sequences |
| What is the total length of the human genome? | 3.08 Gb (3x10^9 bp) |
| What can be done with a sequenced genome? | -understand variation between individuals -find new genes -discover how genomic changes are linked to disease -investigate how organisms are related genetically and how evolutionary pressures have changed genomes |
| What is the significance of an open reading frame? | Open reading frames indicate the likelihood of a gene. Open reading frames begin with a start codon and are long continuous sequences that are not interrupted by a stop codon. |
| What are homologous genes? (homologs) | genes derived from a common ancestral gene |
| What are orthologous genes? (orthologs) | genes in different organisms that share a common ancestral genes (e.g. actin genes) |
| What are paralogous genes? (paralogs) | genes in the same organism that have evolved by gene duplication (e.e. olfactory receptor genes) |
| What is a genetic marker? | a known DNA sequence that can be used to define variation between individuals of the same species |
| What is a phenotypic genetic marker in humans? | loss-of-function disease phenotypes |
| What is a phenotypic genetic marker in Drosophila? | eye color |
| What is a protein genetic marker in Drosophila? | [SGS proteins] |
| What is a protein genetic marker in humans? | MN & ABO blood groups |
| What are two types of general molecular markers? | -sequence tagged sites (STS) -expressed sequence tag (EST) |
| What are three types of alielic molecular markers? | -restriction fragment length polymorphism (RFLP) -variable nucleotide tandem repeat (VNTR) -single nucleotide polymorphisms (SNP) |
| What is an expressed sequence tag? | a short strand of DNA that is generated by sequencing either one or both ends of an expressed gene. These tags can be used to fish out the genomic sequence of a gene by matching base pairs |
| An EST is derived from ______ | cDNA |
| What is a sequence tagged site? | a short (200 to 500 bp) DNA sequence that has a single occurrence in the human genome and whose location and base sequence are known. Detectable by polymerase chain reaction, STSs are useful in localizing and orienting the mapping and sequence data reported from many different laboratories and serve as landmarks on the developing physical map of the human genome |
| What is DNA polymorphism? | One of two or more alternate forms (alleles) of a chromosomal locus that differ in nucleotide sequence or have variable numbers of repeated nucleotide units. |
| What is a variable nucleotide tandem repeat? | A chromosomal locus in which a particular repetitive sequence (microsatellite) is present in different numbers in different individuals or in two different chromosomal homologs in one diploid individual. |
| What are three examples of DNA polymorphism? | -restriction fragment length polymorphism (RFLP) -variable nucleotide tandem repeat (VNTR) -single nucleotide polymorphisms (SNP) |
| What is a single nucleotide polymorphism? | DNA sequence variations that occur when a single nucleo5de (A, T, C, or G) in the genome sequence is altered. |
| What is a restriction fragment length polymorphism? | Variation between individuals in DNA fragment sizes cut by specific restriction enzymes; polymorphic sequences that result in RFLPs are used as markers on both physical maps and genetic linkage maps. RFLPs usually are caused by alterations at a restriction endonuclease cutting site. |
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