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Science Ch 4


heredity the passing of physical characteristics from parents to offspring
trait each different form of a characteristic such as stem height or seed color
genetics the scientific study of heredity
fertilization when egg and sperm join and a new organism begins to form
purebred offspring of many generations that have the same trait
gene factors that control a trait
alleles different forms of a gene; for example, the gene that controls the stem height in peas has one allele for tall stems, another allele for short stems
dominant allele the trait always shows up in the organism when it is present
recessive allele the trait is hidden whenever the dominant allele is present
hybrid one of these has two different alleles for a trait; for example, plants are tall because the dominant allele for tall stems masks the recessive allele for short stems.
probability a number that describes how likely it is that an event will occur
Punnett square a chart that shows all the possible combinations of alleles that come from a genetic cross
phenotype an organism's appearance or physical traits
genotype an organism's genetic makeup or allele combinations
homozygous an organism that has two identical alleles for a trait, for example SS or ss
heterozygous having two different alleles for a trait, for example Ss
codominance a condition in which neither of two alleles in a gene is dominant or recessive
chromosome theory of inheritance according to this, genes are carried from parents to offspring on chromosomes
chromosomes made up of many genes joined together like beads on a string
meiosis chromosome pairs separate and are distributed to two different cells. the resulting cells have only half as many chromosomes as other cells in the organism
genes contain __________ the code that determines the structure of a protein
nitrogen bases the order of these along a gene forms a genetic code that specifies what kind of protein will be produced
mutation can cause a cell to produce an incorrect protein during protein synthesis; for example, changing the order of nitrogen bases on a chromosome on a gene
messenger RNA during protein synthesis, it copies the coded messages from the DNA in the nucleus and carries this message to the ribosome in the cytoplasm
transfer RNA carries amino acids to the ribosome and adds them to the growing protein
Created by: ashie11