Week 2

Question 1

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

Answer 1

Because it ensured homozygousity

Question 2

What is the difference between a purebred and hybrid offspring?

Answer 2

• Purebred: homozygous for each chosen trait
• Hybrid: heterozygous genotype

Question 3

How were Mendel’s experiments designed?

Answer 3

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

Question 4

What is a gene?

Answer 4

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

Question 5

What is an allele

Answer 5

One of two or more alternative forms of a gene

Question 6

What is a characteristic/character?

Answer 6

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

Question 7

What is a locus?

Answer 7

The specific place on a chromosome occupied by an allele

Question 8

What is a genotype?

Answer 8

The set of alleles possessed by an individual organism

Question 9

What is a heterozygote?

Answer 9

An individual organism possessing two different alleles at a locus

Question 10

What is a homozygote?

Answer 10

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

Question 11

What is a phenotype/trait?

Answer 11

The appearance/manifestation of an allele

Question 12

What do dominant alleles determine?

Answer 12

The expressed factor

Question 13

How are dominant alleles denoted?

Answer 13

With an uppercase letter

Question 14

What do recessive alleles determine?

Answer 14

The latent factor (not expressed unless homozygous)

Question 15

What is the P (parental) generation?

Answer 15

The first generation of a genetic cross

Question 16

What is the F1 (first filial) generation?

Answer 16

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

Question 17

What is the F2 (second filial) generation?

Answer 17

• The third generation of a genetic cross
• The offspring of the F1 generation

Question 18

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

Answer 18

Via self-fertilization

Question 19

What is Mendel’s principle of segregation?

Answer 19

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

Question 20

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

Answer 20

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

Question 21

What is Mendel’s principle of independent assortment?

Answer 21

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

Question 22

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

Answer 22

Anaphase I

Question 23

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

Answer 23

Anaphase II of meiosis

Question 24

What is Mendel’s principle of dominance?

Answer 24

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

Question 25

What is the multiplicative rule?

Answer 25

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

Question 26

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

Answer 26

"and"

Question 27

What is the additive rule?

Answer 27

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

Question 28

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

Answer 28

"or"

Question 29

What does binomial probability help determine?

Answer 29

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

Question 30

What is the equation for binomial probability?

Answer 30

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

Question 31

What does each variable in the binomial probability equation represent?

Answer 31

- Equation: P=[n!/(x!y!)](p^x)(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

Question 32

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

Answer 32

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

Question 33

What is a simple cross?

Answer 33

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

Question 34

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

Answer 34

3:1 (A_:aa)

Question 35

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

Answer 35

1:1 (Aa:aa)

Question 36

When does uniform progeny occur?

Answer 36

When all offspring have the same phenotype

Question 37

What types of crosses produce uniform progeny?

Answer 37

- 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)

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

- All progeny are genotypically uniform - AA x AA = all AA - aa x aa = all aa - Aa x Aa = all Aa

Question 41

What is the difference between monohybrid crosses and dihybrid crosses?

Answer 41

- Monohybrid: cross between two individuals that differ in a single characteristic - Dihybrid: cross between two individuals that differ in two characteristics

Question 42

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?

Answer 42

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

Question 43

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)?

Answer 43

- 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

Question 44

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

Answer 44

Four (AB, ab, Ab, aB)

Question 45

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

Answer 45

The law of independent assortment

Question 46

What is a test cross?

Answer 46

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