6.5 Traits and Probability (Biology) – Flashcards
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Who developed the Punnett Square?
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a poultry geneticist named R.C. Punnett
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Punnett square
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a grid system for predicting all possible genotypes resulting from a cross
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What does the grid boxes in a Punnett square show?
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all of the possible genotypes of offspring from those two parents
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What does the axes of the Punnett square represent?
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the possible gamete genotypes of each parent
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How can we find the ratio of genotypes in a generation?
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by counting the number of squares with each genetic combination
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How can we find the ratio of phenotypes in a generation?
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if we know how the genotype corresponds to the phenotype
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monohybrid crosses
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crosses that examine the inheritance of only one specific trait
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testcross
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a cross between an organism with an unknown genotype and an organism with the recessive phenotype
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dihybrid crosses
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- crosses that examine the inheritance of two different traits - has 2 genes or 4 alleles - is heterozygous-heterozygous
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probability
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- the likelihood that a particular event will happen Probability = (# of ways a specific event can occur) __________________________ (# of total possible outcomes)
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You have two coins. The probability that both coins will land heads up is...
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1/2 x 1/2 = 1/4
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law of independent assortment
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- states that allele pairs separate independently of each other during gamete formation, or meiosis - this law can be illustrated using dihybrid crosses - traits are all not on the same chromosome
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law of dominance
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- in a cross of parents that are pure for contrasting traits, only 1 form of the trait will appear in the next generation - all of the offspring will be heterozygous and express only the dominant trait
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law of segregation
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- the formation of gametes (egg or sperm) - the 2 alleles responsible for a trait separate from each other - alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring
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incomplete dominance
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dominant allele is not fully expressed
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codominance
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- 2 alleles are expressed in heterozygous individuals - ex. blood type
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type A blood type
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I^A I^A or I^A i
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type B blood type
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I^B I^B or I^B i
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type AB blood type
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I^A I^B <-- universal donor
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type O blood type
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ii
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What blood types can you recognize if you are positive?
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you recognize anything like AB+
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What blood types can you recognize if you are negative?
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you can ONLY recognize things that are negative
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plasma
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antifluid that are not your blood cells
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sex-linked traits
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traits (genes) located on the sex chromosomes
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sex chromosomes are _ and _
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x and y
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What are the genotypes for females?
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xx
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What are the genotypes for males?
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xy
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hemophilia
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blood clotting not properly
