Chapter 23 Flashcards
learning objective
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learning objective
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mapping
refers to experimental process of deeming the relative locations of genes or other segments of DNA along individual chromosomes
cryogenic mapping
determines locations of specific sequences within chromosomes through staining and binding pattern and are mapped relative to band location
linkage mapping
use the frequency of genetic recombination between different genes to determine their relative spacing and order along a chromosome
physical mapping
DNA cloning techniques are used to determine the location of and distance between genes and other DNA regions
genetic/chromosome map
a diagram that describes the relative locations of genes or other DNA segments along a chromosome
locus/loci
refer to the site within a genetic map where a specific gene or other DNA segment is found
23.2 learning objective
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learning objective
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what does cryogenic mapping do?
determines the locations of specific gene sequences within chromosomes that are viewed microscopically
what are some key differences between eukaryotic chromosomes and bacterial chromosomes?
eukaryotic chromosomes are bigger in size, centromeric location, and different banding patterns
what is one limitation of cryogenic mapping?
it uses light microscopy, so it has limited resolution and can only do about 5 million bp along a chromosome
in situ hybridization
is used to cryogenically map the locations of genes or other DNA sequences within large eukaryotic chromosomes
- situ means the chromes are held in place
- hybridization means a hybrid forms
what does it mean to use a labeled probe?
can use a piece of cloned DNA as a probe so it will complementary attach to the gene of interest
what is FISH?
fluorescence in situ hybridization
what are the steps of the fish procedure?
1) treat cells with agents that make them swell and fixes them onto a slide
2) Denature chromosomal DNA
3) Add single stranded DNA probes that have biotin
4) add fluorescently labeled Alvin that binds to biotin
5) view with a microscope
what is the goal of FISH?
determine the location of the gene within a set of chromosomes
what is the purpose of biotin?
it has a high affinity for a protein called Advin, so when fluorescent Advin is added, it binds with biotin labeled nucleotides and labels the probe
what kind of microscope needs to be used?
fluorescence microscope
what is a common dye used in FISH?
DAPI - it is a fluorescent dye specific for DNA
chromosome painting
using fluorescently labeled probes to identify multiple regions along one ore more chromosomes
23.3 learning objective
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23.3 learning objective
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what is a molecular marker?
a segment of DNA found at a specific site along a chromosome that do not encode genes
- ca be used in PCR and gel electrophoresis
what does it mean for alleles to be polymorphic?
they vary from individual to individual
what are polymorphic genes?
genes found in two or more forms in a population
why are molecular markers useful?
they can be used to determine the approximate location of an unknown gene that causes a human disease
how are molecular markers used in agriculture?
they identify locations of genes involved in quantitative traits like fruit yield and meat weight
microsatellites
short repetitive sequences that are interspersed throughout a species genome and tend to vary in length among individuals
what is the most common micro satellite?
CAn - found about every 10,000 bases in the human genome
what is it called when PCR primers copy a single site within a set of chromosomes?
the amplified region is called sequence tagged site (STS)
what is the result of an STS?
produces only one band on a gel from haploid cells, two copies on diploid cells
23.3
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23.3
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23.3
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23.3
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23.3
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23.3
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23.3
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23.3
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23.4 learning objective
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23.4 learning objective
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23.4 learning objective
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how big is the human genome?
3 billion bp in length
what is a DNA library?
a collection of recombinant vectors where every vector contains a fragment of DNA
what is a contig?
a collection of clones that contain contiguous, overlapping pieces of DNA
how do you construct a contig?
large pieces of DNA are cloned into vectors, their order is determined by the identification of overlapping regions
what is the goal for physical mapping?
to obtain a complete contig for each type of chromosome within a full set
why are artificial chromosomes needed?
to make contigs, vectors need to be able to accept long segments of DNA so there are fewer vectors needed. However, it doesn’t work with too long of strands. artificial chromosomes can accept much larger segments
what are some types of artificial chromosomes?
1) yeast artificial chromosomes (YAC)
2) bacterial artificial chromosomes (BAC)
3) P1 artificial chromosomes (PACs)
YAC
a cloning vector in yeast that can accommodate several hundred thousand to 2 million bp segments of DNA
- it only takes a few hundred YACs to create a contig for an entire chromosome
BAC
- developed from F factors
- contains several genes that function in vector replication and segregation
- contains unique restriction enzymes
- lengths up to 300,000
AC
- developed from p1 bacteriophage
- lengths up to 300,000
cosmid
a vector that is a hybrid between a plasmid vector and a phage. can replicate in a cell like a plasmid or be packaged into a protein like a phage
why are cosmids needed?
they accept smaller sizes, about tens of thousands bp in length
