Genetics

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Melosis

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Process of making gametes(4 genetically different cells from one parent cell) occurs in two different phases (I or II)

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Haploid

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Cell that contains only one copy of chromosome set (Chromosomes in human gametes)

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Diploid

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Dell with PAIRS of homologous chromosomes (46 chromosomes in humans)

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Gamete

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Sex Cell (sperm or egg) always haploid, so when combined together, a diploid organism is created

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Crossing Over

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Occurs in prophase I of meiosis: genes are exchanged between two chromosomes, which leads to genetic diversity (reason why the 4 daughter Cells are genetically different.

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Gene

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Segment of repeating nucleotides in DNA that codes for trait

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Allele

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Alternative form of a gene located at a specific point on a chromosome (Hh has two different alleles: H and h)

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Dominant Trait

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Trait that appears over a recessive form when both are present

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Recessive Trait

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A trait that does not appear unless the dominant trait is absent (cc represents an individual who has Cystic Fibrosis, which is recessive)

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Homozygous

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Two identical alleles (HH or hh) homo=same

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Heterozygous

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Two non identical alleles (HH or hh) hetero=different

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Carrier

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An individual who has an allele for a recessive trait, but does not express it because a dominant one overrules it (CC is a carrier of Cystic Fibrosis, a recessive condition

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Genotype

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GENetic make up of a trait (RR, Rr or rr)

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Phenotype

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PHysical appearance of a trait (round or wrinkled peas)

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Punnett Square

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A diagram/chart used to predict the outcome of a certain pair of mating individuals based on one trait. (AKA: monohybrid cross)

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Pedigree

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Graphic diagram showing relationship within a family (circles=females and squares=males shaded=affected by a certain trait and unshaded=not affected)

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Co-Dominance

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Both alleles show dominance in true form (red plus white=splotchy red and white)

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Incomplete Dominance

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neither allele is completely dominant over the other, so the blend together (red plus white=pink)

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Sex-Linked Trait

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Trait Carried on the X chromosome, which causes the trait to appear most often in males when the Y chromosome is incapable of showing dominance over the trait.

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Nondisjunction

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Failure of chromosomes to seprate; Causes genetic disorder

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Down Syndrome

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(Trisomy 21) Occurs when an individual has 3 chromosomes on 21st pair instead of 2; caused by NONDISJUNCTION

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Karyotype

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Pictographic spread of an individual's chromosomes grouped in homologous pairs: all normal humans have 46