Genetics Glossary
- allele
- One of two or more alternative forms of a gene. In diploid cells two alleles occupy the same locus on a homologous pair of chromosomes
- centriole
- Two cylindrical structures assembled from microtubules. During prophase the centrioles are doublicated and start migrating to opposite sides of the nucleus.
- centromere
- Central region on a chromosome. After replication the microtubules . During prophase the centrioles are doublicated and start to migrate to opposite sides of the nucleus.
- chromatin
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Dense complex consisting of double helix DNA and histones. Sub-structures are nucleosomes, which condense into chromatin fibers. See your textbook for illustration.
- chromosome
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A very long segment of DNA and associated proteins composed of genes which carry all or part of the hereditary information of the organism.
- diploid
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Two set of chromosomes. This means that there are also two copies of each gene. The DNA in somatic cells is diploid
- eukaryotic
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A eukaryotic cell has nucleus and cellular organelles such as mitochondria, rough ER smooth ER, Golgi etc.
- DNA
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See Sructure of DNA
- gamete
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A sperm or egg cell for sexual reproduction. Gamets are haploid cells which have only one copy of each chromosome.
- gene
- A segment of DNA which encodes am-RNA (which is translated into a protein), a t-RNA or a r-RNA. This segment of the DNA may include control sequences for the xpression of the gene.
- genotype
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The genetic make up of an individual, i.e. all the genes present in a person. Compare to phenotype.
- haploid
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Having only one copy of each chromosome.
Sperm or egg cells (gametes)are haploid, compared to somatic cells which are diploid is located.
- heterozygous
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Having two different alleles of the same gene.
- homologous chromosome
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One of two copies of a chromosome . One copy is derived from the male parent and the other copy is derived from the female parent
- homozygous
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Having two identical alleles of the same gene.
- kinetochore
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Specialized proteins near the centromer region of prophase chromosomes. They serve as attachment anchor for the microtubules radiating out from the centrioles .
- locus
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The position on a chromosome where a gene is located.
- meiosis
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Process of cellular division which produces egg or sperm cells. After replication an initially diploid cell undergoes two divisions, resulting in four haploid daughter cells.
- mitosis
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Division of the cellular nucleus containing replicated DNA. During mitosis the replicated chromosomes are separated into two identical sets , one for each daughter cell. Cell proliferation proceeds via mitosis.
- microfilaments
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filamentous protein fibers. Like microtubles microfilaments are part of the cytoskeleton which supports cell shape. They also play a role in muscle contraction, since muscle fibers are composed of microfilaments
- microtubule
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Cylindrically shaped protein fibers. Microtubles are part of the cytoskeleton which supports cell shape, they also play a role in cellular motility and growth
- nucleotide
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Basic building block molecule of DNA or RNA. Consists of ribose or deoxyribose, nucleic acid base and phosphate. See DNA Structure
- phenotype
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The traits that an individual expresses, e.g. a flower has three genotypes AA, Aa and aa , but only two phenotypes, purple and white.
- prokariotic
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A prokariotic cell has no nucleus and no cellular organelles. Bacteria are prokariotes.
- somatic cells
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Any cell of an organism except cells which form gametes