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What is a chromosome mutation or chromosomal aberation?
Large changes in chromosome structure.
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What is a genome mutation?
A change in chromosome number. (change in number of sets or number of individuals in a set)
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What are the four chromosomal classifications?
- Meta
- Submeta
- Acro
- Telocentric
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Describe the chromosomes found in a karyotype.
- Short p arms are on top.
- Long q arms are on the bottom.
- Larger chromosomes have smaller numbers and numbers increase with diminishing size.
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What is G banding?
- Mild heat or enzymes that partially digest chromosomal proteins.
- Exposed to Giemsa dye.
- Banding patterns help distinguish similar chromosomes and dectection of structural changes.
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What are the two primary ways that chromosomes can be altered?
- Total amount of genetic material within a single chromosome can be increased or decreased.
- Genetic material in one chromosome can be rearranged without affecting the total amount of genetic material.
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What are the two ways genetic material can be lost or gained?
- Deletion (deficiency): occurs when a segment of chromosome is lost.
- Duplication: occurs when a section of a chromosomeis repeated compared to the normal parental chromosome.
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What are the two types of deletions?
- Terminal deficiency: single break, a piece without centromere is lost and degrades.
- Interstitial deficiency: two breaks, central fragment is lost and two outer pieces reattach to each other.
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Cri-du-chat syndrome, Angelman & prader willi syndrome, Smith-Magenis Syndrome, are all examples of what?
Deletions
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What do duplications normally occur from?
Result from abnormal events during recombination. (unequal crossing over between homologous chromosomes and sister chromotids.
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What is a gene family and how are the formed?
- Two or more genes that are similar to each other.
- Accumulation of small chromosomal duplications can over the course of many generations.
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What are homologous genes?
Two or more genes derived from a single ancestral gene.
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What is the difference between Paralogs and Orthologs?
Homologous genes within a single species are paralogs; while homologous genes found in multiple species are called orthologs.
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How are paralogs and orthologs derrived?
- Paralogs: result of duplications
- Orthologs: result of speciation
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What is the difference between pericentric and paracentric inversions?
- Pericentric inversion: Centromere lies within the inverted region.
- Paracentric inversion: Centromere is found outside the inverted region.
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Why do most inversions have no phenotypic effects?
The gene's promotor and coding sequence are maintained in the same direction, so transcription can still occur.
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What is a disorder is caused by a breakpoint in a vital gene due to inversion?
Hemophilia (Type A) X linked inversion
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What is an Inversion Heterozygote?
An individual with one normal and one inverted chromosome.
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What is an inversion loop?
During meiosis 1, an inversion loop forms to permit the homologous genes on both chromosomes to align.
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If crossing over takes place when a gene has a pericentic inversion, what happens?
It leads to duplication/ deletion of genetic material.
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If crossing over takes place when a gene has a paracentric inversion, what happens?
Formation of both Dicentric and Acentric chromosomes. This causes the dicentric chromosome to be pulled apart and the acentric chromosome to be lost or degraded.
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What is a translocation?
One segment of a chromosome breaks off and becomes attached to a different chromosome.
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What are telomeres?
ends of chromosomes containing tandemly repeating sequences. Their purpos is to preven the attachment of DNA to the ends of chromosomes.
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What are reactive ends and what are the consequences of having them?
- Broken ends of chromsomes that lack telomeres.
- DNA repair enzymes may join broken pieces of different chromosomes together to produce abnormal chromosomes.
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What are the two types of nonhomologous crossing over?
- Reciprocal translocation
- Simple translocation
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What is reciprocal translocation?
produced when two non homologous chromosomes swap parts.
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What is a simple translocation?
produced when a fragment from one chromosome is attached to andother chromosome (unbalanced).
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What is a What is an example of a simple translocation?
Familial down syndrome.
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What is a Robertsonian translocation?
A type of simple translocation where the centromeric region of two non homologous acrocentric chromosomes become fused to form a single chromosome.
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What is Euploidy?
Having the total chromosome number that is exact multiple of a chromosome set.
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What is aneuploidy?
Alteration in chromosome number so that the total number is not an exact multiple of a set.
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What is nondisjunction?
Full segregation of chromosomes is not obtained. Either bivalents in Meiosis 1 or sister chromotids in Meiosis 2.
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Down syndrome, edward syndrome, and patau syndrome are the result from what?
Trisomy
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What are two aneuploid condiditons in sex chromosomes?
- Klinefelter (XXY)
- Turner (XO)
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What is endopolyploidy?
- Variation in euploidy can be restricted to certain tissues.
- The mechanism of formation is mitosis without cytokinesis.
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What is a Chromocenter?
Where all polytene chromosomes are attached.
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What are the three natural ways chromosome composition can vary?
- Meiotic nondisjunction
- Mitotic nondisjunction
- Autopolyploidy
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What is autopolyploidy?
An organism or part of an organism having more than two sets of chromosomes all derived from the same species.
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What is allopolyploidy?
An organism with sets of chromosomes from two or more different species. Hybrids.
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What is allotetraploidy?
Diploid for two genomes from a different species.
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What are homeologous chromosomes?
Are evolutionarily related chromosomes from two different species that can properly synapse during meiosis to create haploid gametes. Fertile offspring.
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What are NonHomeologous chromosomes?
Produce sterile offspring.
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What is a heterokaryon?
A cell containing two nuclei. It will spontaneously go through nuclear fusion to create a hybrid cell with a single nucleus.
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What is parthenogenesis?
Inducement of egg to begin development without fertilization.
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What is an Anther culture (androgenesis)?
A method of breading in order to selectively weed out recessive alleles of a plant.
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