Genetics. What is Genetics?. The branch of biology that seeks to explain biological variation Heredity: Transmission of characteristics (traits) from parent to offspring. Vocab You Should Recall:. Diploid- a cell with 2 sets of homologous chromosomes (2n) Haploid-
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Phenotype = Genotype + Environment.
Genetically identical hydrangeas growing in soils of different acidity (different environments).
The phenotype = genotype + environment principle applies equally to human traits.
Free ear lobes (dominant trait)
Attached ear lobes (recessive trait)
Dimples (dominant trait)
No dimples (recessive trait)
Rolling up edges (dominant trait)
not rolling (recessive)
In order for Dolly to be a non-tongue roller, her mom has to be heterozygous for tongue rolling
Segregation of alleles in meiosis & uniting of a certain egg and sperm is random, like a coin flip.
If my friend Victoria and her husband Peter are carriers of cystic fibrosis and have already had a son with the disorder, what are their chances of having another child with the disorder?
¼ or 25%
Ex. The probability of flipping a coin and getting 2 tails in a row:
The probability of flipping tails on the 1st penny= ½
The probability of flipping tails on the 2nd penny= ½
The probability of getting tails on both pennies=¼
Ex. The probability of flipping 1 head and 1 tail in a toss with 2 coins:
The probability of flipping tails on the 1st penny and heads on the 2nd penny = (½)(½) = ¼
The probability of flipping heads on the 1st penny and tails on the 2nd penny= (½)(½) = ¼
The probability of getting one tail and one head in a toss with 2 coins = ½
½ x ½ x ½ x ½ = 1/16 or 6.25%
What is the probability of my friend Victoria and her husband having two kids with cystic fibrosis?
¼ x ¼ = 1/16
The past outcomes of coin flips greatly affect the outcomes of future coin flips.
You must flip the coin many times.
Therefore, the _____ the number of offspring from a genetic cross, the closer the resulting numbers will get to expected values.
For a coin, you can toss heads or tails
For a die, the degrees of freedom would be
6 – 1= 5
Consider a cross between parents heterozygous for both deafness and albinism.
This is the same 9:3:3:1 ratio seen for Mendel’s cross involving pea color and shape.
What genotypic and phenotypic ratios are matings between cream-colored individuals likely to produce?
yellow: cream: white
a. red x roan:
b. white x roan:
c. red x white:
d. roan x roan:
1:1 RR:Rr 1:1 Red: Roan
1:1 Rr:rr 1:1 Roan:White
All Rr all Roan
1:2:1 RR:Rr:rr 1:2:1 Red:Roan:White
Anemia, infections, weakness, impaired growth, liver and spleen failure, death.
Traits (phenotypes) associated with the sickle cell allele.Pleiotropy
Temperature sensitive –
The cold extremities (ears, nose, tail, and feet) express pigmentation while the warm body does not)
Height in humans is polygenic. Each upper case letter adds 3”. Males (aabbcc) are 5’ and females (aabbcc) are 4’ 7”.
How tall would a male with the genotype AaBbCc be?
Probability that mating with this male & female result in a child that is homozygous recessive for all three traits?
(1/4)3 = 1/64
How tall would that child be if it were a girl?
PPCC and ppcc
9: Dominant for both traits
3: Dominant for first trait and recessive for second
3: Recessive for first trait and dominant for second
1: Recessive for both traits
What are the phenotypes?