# 6.5 Traits and Probability (Biology) – Flashcards

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Who developed the Punnett Square?
a poultry geneticist named R.C. Punnett
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Punnett square
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?
all of the possible genotypes of offspring from those two parents
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What does the axes of the Punnett square represent?
the possible gamete genotypes of each parent
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How can we find the ratio of genotypes in a generation?
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?
if we know how the genotype corresponds to the phenotype
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monohybrid crosses
crosses that examine the inheritance of only one specific trait
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testcross
a cross between an organism with an unknown genotype and an organism with the recessive phenotype
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dihybrid crosses
- crosses that examine the inheritance of two different traits - has 2 genes or 4 alleles - is heterozygous-heterozygous
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probability
- 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...
1/2 x 1/2 = 1/4
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law of independent assortment
- 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
- 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
- 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
dominant allele is not fully expressed
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codominance
- 2 alleles are expressed in heterozygous individuals - ex. blood type
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type A blood type
I^A I^A or I^A i
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type B blood type
I^B I^B or I^B i
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type AB blood type
I^A I^B <-- universal donor
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type O blood type
ii
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What blood types can you recognize if you are positive?
you recognize anything like AB+
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What blood types can you recognize if you are negative?
you can ONLY recognize things that are negative
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plasma
antifluid that are not your blood cells
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traits (genes) located on the sex chromosomes
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sex chromosomes are _ and _
x and y
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What are the genotypes for females?