Bio Ch 23 - Example- inheritance of a widows peak vs. a...

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Ch. 23 Patterns of Inheritance 23.1 Mendel’s laws Gregor Mendel Published a paper in 1866 stating that parents pass discrete heritable factors on to their offspring Factors retain individuality generation after generation Identified that each trait is inherited by a pair of factors, one from each parent One form of a factor may be dominant over an alternative form Reasoned that each egg and sperm must contain only 1 copy of a factor for each trait Mendel’s law of segregation Each individual has two factors (genes) for each trait The factors segregate (separate) during the formation of gametes Each gamete contains only one factor from each pair of factors Fertilization gives each new individual 2 factors for each trait What we know now Genes are sections of chromosomes Chromosomes come in pairs called homologous pairs Homologous pairs have genes controlling the same traits Genes are located at the same point or locus, on each member of the pair Information contained within the homologous genes is not necessarily the same (ex: blues vs. brown eyes) Alternative forms of a gene for a trait are called alleles Gene locus Inheritance of a single trait Capitol letter- represents the dominant allele Small letter- represents the recessive allele Dominant-a certain trait will result if the individual has at least 1 dominant allele Recessive- for a recessive trait to result the individual must have 2 copies of the recessive allele Genotype- genetic composition of an individual with regard to a specific trait 2 copies of the dominant allele- homozygous dominant 1 copy of the dominant allele and 1 of the recessive- heterozygous 2 copies of the recessive allele- homozygous recessive Phenotype- physical appearance of the individual with regard to a trait Homozygous dominant individual and heterozygous individual will have the same genotype in this instance Homozygous recessive individual will have a different phenotype Example- inheritance of a widow’s peak vs. a straight hairline in people Alternative forms of alleles for hairline shape Widow’s peak is dominant to straight W=allele for widow’s peak w= allele for straight hairline Widow’s peak Gamete formation During meiosis, homologous chromosomes separate so there is only 1 member of each pair in a gamete There is one allele for each trait, such as hairline, in each gamete No two letters in a gamete can be the same letter of the alphabet If genotype is Ww, then gametes from this individual will contain either a W or a w If the genotype is WwLl (looking at 2 traits), gametes can contain any of the following combinations » WL, Wl, wL, or wl Practice problems For each of the following genotypes, give all possible gametes WW WWSs Tt Ttgg AaBb For each of the following, state whether the genotype or a gamete is represented
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This note was uploaded on 03/30/2008 for the course BIO 105 taught by Professor Mickle during the Spring '07 term at N.C. State.

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Bio Ch 23 - Example- inheritance of a widows peak vs. a...

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