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BIOL*1090 > Week 2 > Flashcards

Week 2 Flashcards

Mendelian genetics, probabilities, binomial equation, and dihybrid crosses

1
Q

Why was it important that Mendel’s peas were highly in-bred?

A

Because it ensured homozygousity

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2
Q

What is the difference between a purebred and hybrid offspring?

A
  • Purebred: homozygous for each chosen trait
  • Hybrid: heterozygous genotype
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3
Q

How were Mendel’s experiments designed?

A

In a way that allowed him to study one trait at a time

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4
Q

What is a gene?

A

An inherited factor (encoded by DNA) that helps determine a characteristic

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5
Q

What is an allele

A

One of two or more alternative forms of a gene

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6
Q

What is a characteristic/character?

A

An attribute or feature possessed by an organism (determined by allele)

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7
Q

What is a locus?

A

The specific place on a chromosome occupied by an allele

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8
Q

What is a genotype?

A

The set of alleles possessed by an individual organism

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9
Q

What is a heterozygote?

A

An individual organism possessing two different alleles at a locus

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10
Q

What is a homozygote?

A

An individual organism possessing two of the same alleles at a locus

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11
Q

What is a phenotype/trait?

A

The appearance/manifestation of an allele

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12
Q

What do dominant alleles determine?

A

The expressed factor

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13
Q

How are dominant alleles denoted?

A

With an uppercase letter

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14
Q

What do recessive alleles determine?

A

The latent factor (not expressed unless homozygous)

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15
Q

What is the P (parental) generation?

A

The first generation of a genetic cross

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16
Q

What is the F1 (first filial) generation?

A
  • The second generation of a genetic cross
  • The offspring of the parents in the P generation
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17
Q

What is the F2 (second filial) generation?

A
  • The third generation of a genetic cross
  • The offspring of the F1 generation
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18
Q

In Mendel’s experiments, how did the F1 generation reproduce?

A

Via self-fertilization

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19
Q

What is Mendel’s principle of segregation?

A

Each individual organism possess two alleles at one locus (one from each parent)

20
Q

What three observations led Mendel to conclude the principle of segregation?

A
  • Each individual organism possesses two alleles encoding a trait
  • Alleles separate when gametes are formed
  • Alleles separate in equal proportions
21
Q

What is Mendel’s principle of independent assortment?

A

Alleles at different loci separate independently (ex. allele at locus for wrinkled vs round is at a different locus than the allele for plant height

22
Q

Assuming no crossing over occurs, when do segregation and independent assortment take place?

A

Anaphase I

23
Q

If crossing over takes place, where might segregation and independent assortment take place?

A

Anaphase II of meiosis

24
Q

What is Mendel’s principle of dominance?

A

In a heterozygote, one allele may conceal the presence of another

25
Q

What is the multiplicative rule?

A

If events A and B are independent, the probability that they occur together is the product of their individual probabilities

26
Q

What is the key word indicating the multiplicative rule should be used?

A

“and”

27
Q

What is the additive rule?

A

If events A and B are independent and do not overlap, the probability that at least one of them occurs is the sum of their individual probabilities

28
Q

What is the key word indicating the additive rule should be used?

A

“or”

29
Q

What does binomial probability help determine?

A
  • Any combination of events
  • the probability that for n progeny, exactly x will fall into one class and y into another
30
Q

What is the equation for binomial probability?

A

P=[n!/(x!y!)] (p^x) (q^y)

31
Q

What does each variable in the binomial probability equation represent?

A
  • Equation: P=n!/(x!y!)(q^y)
  • P= overall probability of event X and Y
  • n= total number of potential outcomes (x+y)
  • x= the number of times we want X to occur
  • y= the number of times we want Y to occur
  • p= probability of X occurring
  • q= probability of Y occurring
32
Q

What two conditions need to be met when using the binomial equation?

A
  • There are only two possible outcomes (ex. affected vs unaffected)
  • Each event is independent of the other
33
Q

What is a simple cross?

A

A single locus is under consideration and one of the alleles is dominant to the other

34
Q

What is the phenotypic ratio of offspring when both parents are heterozygous?

A

3:1 (A_:aa)

35
Q

What is the phenotypic ratio of offspring when one parent is heterozygous and the other is homozygous recessive?

A

1:1 (Aa:aa)

36
Q

When does uniform progeny occur?

A

When all offspring have the same phenotype

37
Q

What types of crosses produce uniform progeny?

A
  • Any cross between two homozygotes (AA x AA, aa x aa, AA x aa)
  • Homozygous dominant and heterozygous (AA x Aa) (dominant trait will be expressed in all progeny)
38
Q

What is the genotypic ratio of offspring when both parents are heterozygous?

A

1:2:1 (AA:Aa:aa)

39
Q

What is the genotypic ratio of offspring when one parent is heterozygous and the other is homozygous (dominant or recessive)

A

1:1 (Aa:AA or Aa:aa)

40
Q

What is the genotypic ratio of offspring when both parents are homozygous (dominant or recessive)?

A
  • All progeny are genotypically uniform
  • AA x AA = all AA
  • aa x aa = all aa
  • Aa x Aa = all Aa
41
Q

What is the difference between monohybrid crosses and dihybrid crosses?

A
  • Monohybrid: cross between two individuals that differ in a single characteristic
  • Dihybrid: cross between two individuals that differ in two characteristics
42
Q

In a dihybrid cross, what is the genotypic ratio of offspring when one parent is homozygous dominant for both traits and the other is homozygous recessive?

A

All progeny are heterozygous at both loci (AABB x aabb = all AaBb)

43
Q

In a dihybrid cross, what is the phenotypic ratio of offspring when both parents are heterozygous for both traits (the F2 generation in Mendel’s dihybrid cross)?

A
  • 9:3:3:1
  • dom both traits : dom trait 1 and rec trait 2 : dom trait 2 and rec trait 1 : rec both traits
  • Mendel’s cross - round, yellow : round, green : wrinkled, yellow : wrinkled, green
44
Q

How many different gametes can be produced in a dihybrid cross of a parent who is heterozygous for both traits (AaBb)?

A

Four (AB, ab, Ab, aB)

45
Q

Which of Mendel’s laws allows multigene crosses to be broken down into multiple monohybrid crosses?

A

The law of independent assortment

46
Q

What is a test cross?

A

An individual with an unknown genotype is crossed with an individual who is homozygous recessive to determine the genotype of the unknown individual

47
Q
A

BIOL*1090 (15 decks)

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