Bio I Lab

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centromere

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primary constriction

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karyotype

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is an assemblage of metaphase chromosomes of an individual arranged in pairs according to the order of descending length and position of the centromere.

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metacentric chromosome

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is one that has a centrally located centromere and chromosome arms with approximately equal length.

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submetacentric chromosomes

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have centromeres located close to the center of the chromosome, but he chromosome arms are distinctly unequal in length.

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acrocentric chromosomes

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have centromeres located much nearer one end than the other, resulting in chromosome arms that are decidedly unequal in length.

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telocentric

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no human chromosomes have centromeres on the end(telocentric), thus having only one arm.

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secondary constrictions

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human chromosomes that usually represent the site of ribosomal RNA genes.

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satellites

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short, distal, chromosomal portions.

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region

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an area of a chromosome between two major landmarks such as centromere, conspicuous band, or chromosome end.

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bands

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within each region are numbered starting with the band closest to the centromere and proceeding toward the end of each chromosome arm.

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syndrome

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a complex of symptoms that may include aneuploidies with morphological, physiological, and psychological deviations form normal.

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DNA molecules have areas that

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are not genes, called junk DNA.

Junk DNA is thought to play important roles in cellular metabolism and inherited diseases.

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RFLP Analysis

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is one of the original processes used to create a DNA profile.

Restriction Fragment Length Polymorphism.

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Restriction Enzymes

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enzymes that cut the DNA molecule at specific sites

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Gel Electrophoresis

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A process that separates fragments of DNA.

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Gel

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is a thin sheet of gelatin supported by a glass plate with electrodes atached at both ends.

One end of the gel has a positive charge and the other end has a negative charge.

DNA fragments are attracted to the positive end of the gel plate.

Smaller, lighter fragments migrate more easily through the gel and therefore travel farther in a given time period than larger, heavier fragments.

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Molecular probes

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small pieces of DNA that use the base-pairing rule to locate and bind only to the fragments that will be used to form the DNA profile.

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X-ray film

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photographs the sheet of DNA bands.

the only bands visible on the developed film are those that have been labeled with molecular probes.

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DNA Restriction Analysis

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is a method that uses bacterial enzymes known as restriction endonucleases or restriction enzymes to reveal exact nucleotide sequences.

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Restriction Map

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can be produced with the information obtained through the use of restriction enzymes that cut DNA molecules, such as circular viral DNAs, into specific fragments.

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bacteriophage

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a virusthus infects bacteria.Particular forms such as lambda are used as vectors for cloning DNA.

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bp(base pair)

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a pair of complementary nitrogeneous bases in a DNA molecule; also the unit of measurement for DNA sequences.

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cathode

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the negative electrode from which electrons are emitted; opposite of the anode.

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endonuclease

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a class of enzymes that degrades DNA and/or RNA molecules that cleave bonds linking adjacent nucleotides

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evolution

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is a change in the genetic composition of a population.

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evolution results

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from a change in the frequency of the alleles in the gene pool produced by one or more of the following factors:

mutation, gene flow, natural selection, genetic drift, or nonrandom mating.

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mutation

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the naturally occurring mutations of genes and chromosomes produce variation in the gene pool.

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gene flow

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the frequency of alleles in the gene pool may change due to the immigration of emigration of organisms.

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natural selection

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the impact of the environment on the survival and reproduction of genotypes within the population is a major force in changing the frequency of alleles.

Selection is always on the phenotypes, but the genetic effect is on the genotypes.

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genetic drift

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the frequency of alleles in the gene pool may change by pure chance.

It is a significant evolutionary mechanism in small populations only.

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nonrandom mating

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If there is a mating preference for a certain combination of alleles, the frequency of alleles in a population will change.

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Castle-Hardy-Weinberg (CHW) law or Equilibrium

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states that in the absence of forces that change gene frequencies, the frequencies of the alleles in a population will remain constant from generation to generation.

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CHW equation

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p2 + 2pq + q2 = 1

p2 = the frequency of TT individuals(homozygous dominants)

2pq= the frequency of Tt individuals(heterozygotes)

q2 = the frequency of tt individuals (homozygous recessives)

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systematics

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the classification of organisms and groups of organisms.

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species

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are groups of actually or potentially interbreeding natural populations, which are reproductively isolated form other such groups.

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Chromosomes are arranged by:

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size,
location of centromere

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Chromosomal Alterations

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Errors during meiosis lead to abnormalities

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deletion

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Chromosomes
Lose a piece

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translocation

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Chromosomes Recombine with a non-homologous chromosome

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Errors during recombination (Meiosis I)

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can result in some chromosomal abnormalities.

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Chromosomal aberrations fall into three general categories:

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Translocation/Chromosomal Breaks
Deletion
Fragile site

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Polyploidy

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presence of additional sets of chromosomes
Common in plants Lethal in most animals

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Aneuploidy

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presence of extra chromosome or an absence of one

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Trisomy

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“three bodies” – having one extra chromosome

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Monosomy

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missing a chromosome

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Meiotic nondisjunction causes

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the gain or loss of single chromosomes

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Aneuploid Condition:

Trisomy 21

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Down Syndrome

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Aneuploid Condition:

Trisomy 18

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Edwards Syndrome

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Aneuploid Condition:

Trisomy 13

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Patau Syndrome

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Chromosome Breaks

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Spontaneous breaks due to errors in DNA replication & errors in crossing-over
Environmental factors: UV light, Radiation, Viruses, Chemicals
Cri du Chat: Caused by partial deletion of Chromosome 5
Infant’s cry sound like a cat. Speech problems after infancy.  abnormal glottis & larynx

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Sex Chromosome Aneuploidy

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is more common than Autosome Aneuploidy

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Turner Syndrome

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Female (45 total chromosomes, 1 sex chromosome (X))
Only monosomy that is Not lethal
Abnormalities: don’t develop normal at time of puberty, underdeveloped breasts, rudimentary ovaries
Infertile: do Not ovulate or menstruate
Treatment: Hormone supplements can help these women lead normal lives.

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Fragile Sites

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Fragile X Syndrome: normally CGG is repeated 50 times; in fragile X, up to 1000 times
Makes a very thin physical region of the chromosome.
Results in range of mental retardation and behavioral problems
Occurs in both sexes; most females with fragile X are heterozygous