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Genetics Study Guide
genetics - the scientific study of heredity
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heredity - the passing of traits, or physical characteristics, from
parents to their offspring
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traits- the physical characteristics of an individual
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genes – found on chromosomes and determine the physical traits
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purebred -organism produces offspring with the same form of a trait
as itself
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P1 - refers to the first generation purebred individuals.
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F1 - stands for the first filial generation (filial means “son” in Latin);
also known as hybrids
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hybrids- organisms that have both a dominant and recessive allele
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alleles - different forms of genes are called
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dominant alleles- control traits that can be seen in the offspring when
present; represented by a upper case letter
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recessive alleles – control traits that can be masked or hidden by the
presence of a dominant allele; represented by a lower case letter
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Punnett squares- show the likelihood, or probability, that a trait will
be present in offspring.
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phenotype- the physical traits displayed by an organism
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genotype- the genetic makeup or allele combination an organism has
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homozygous- two identical alleles
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heterozygous- hybrids having two different alleles
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codominance- when alleles are neither dominant or recessive
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multiple alleles- three or more forms of a gene
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chromosomes - composed mostly of DNA and carry genes
DNA - made up of nitrogen bases:
adenine (A) connects to thymine (T)
guanine (G) connects to cytosine (C)
sex-linked genes – carried on the sex chromosomes, X and Y
meiosis- process in which a parent cell divides
to produce daughter cells with half the
number of chromosomes