Gene Segregation and Interaction

Question 1

can be analyzed through transmission of visible characteristics in pea plants

Answer 1

Genes

Question 2

Homologus chromosomes combine at ___ stage of meiosis I

Answer 2

pachytene

Question 3

Segregation of genes commenced at ____

Answer 3

anaphase I

Question 4

The analysis of genetic crosses depends upon the understanding of Mendel’s two las

Answer 4

Principle of Segregation
Principle of Independent Assortment

Question 5

demonstrates that two members of a gene pair (alleles) segregate (separate) from each other in the formation of genes

Answer 5

principle of segregation

Question 6

indicates that the genes for different traits separate independently of one another and combine randomly in the formation of gametes during meiosis

Answer 6

principle of indepdendent assortment

Question 7

what mathematical tool is used to determine “goodness of fit”

Answer 7

chi-square test

Question 8

null hypothesis for the observed phenotypic ratio

Answer 8

There is no significant difference between the observed phenotypic ratio and the expected phenotypic ratio

Question 9

deviatio nformula

Answer 9

d^2 = (O-E)^2

Question 10

after getting the deviation, what should be done

Answer 10

d^2/E

Question 11

N is the

Answer 11

total number of observations

Question 12

degrees of freedom formula

Answer 12

n-1

Question 13

2. Explain Mendelian laws of heredity. Correlate them with the specific events of meiosis (5 pts).

Answer 13

Mendelian laws of heredity propose three laws: law of dominance, where one trait hides the other trait for the same characteristics. Law of segregation, which explains two parents possess traits that only one trait of these individuals can be passed to the offspring. Lastly, the law of independent assortment, that describes alleles of two or more different genes typed into gametes independently.
Law of segregation can be witnessed during meiosis 1, where homologous chromosomes separate, each daughter cells will only have one chromosome per each pair. This process is a basis for the law of segregation.1 In addition, these chromosomes assort independently (law of independent assortation), where one pair of chromosomes does not affect the orientation of the other pair, which leads to an assortment of genes.2

Question 14

a. Chi square

Answer 14

The Chi-square test is a statistical method used to compare observed and expected values. In genetics, it helps us to decide whether to accept or reject a given hypothesis about genetic inheritance. This test allows us to analyze and interpret the relationship between two genes.

Question 15

b. Gene segregation

Answer 15

Gene segregation is a process where alleles separate during meiosis to ensure that the parent’s traits are passed down to the offspring. It promotes genetic variation within a population instead of inheriting a blend of the parent’s traits. It can also take place in small populations where individuals share a common ancestry

Question 16

c. Probability

Answer 16

Probability refers to the likelihood of a specific genetic outcome occurring in offspring. It is used to predict the possible genotypes and phenotypes of offspring based on the genetic makeup of the parents. Probability follows the laws of chance, meaning larger sample sizes tend to yield results closer to predicted ratios (such as Mendel’s 3:1 phenotypic ratio in monohybrid crosses).

Question 17

d. Random mating

Answer 17

Random mating refers to a reproductive process in which individuals’ pair by chance rather than according to specific genetic traits. This means that everyone in a population has an equal opportunity to mate with any other individual, regardless of genotype or phenotype (if they are compatible for reproduction).

Question 18

A woman has a rare abnormality of the eyelids called ptosis, which makes it impossible for her to open her eyes completely. The condition has been found to depend on a single dominant gene (P). The woman’s father had ptosis, but her mother had normal eyelids. Her father’s mother had normal eyelids.

a. What are the probable genotypes of the woman, her father, and her mother?

Answer 18

• Since the woman has ptosis, her genotype could be either PP or Pp. But since her mother has normal eyelids (pp), so she must have inherited a ‘p’ allele from her mother. Therefore, the woman’s genotype is Pp.
• The woman’s mother has normal eyelids, meaning she has two copies of the recessive allele, making her genotype as pp.
• The woman’s father has ptosis, so his genotype has at least one ‘P’ allele. His mother had normal eyelids (pp), so he must have inherited a recessive ‘p’ allele from her. Thus, the father’s genotype is Pp.

o The summary of the family’s genotypes are the following:
 Woman: Pp
 Her father: Pp
 Her mother: pp

Question 19

b. What proportion of their children will be expected to have ptosis if she marries a man with normal eyelids?

Answer 19

Based on the Punnett square above, PP represents children with ptosis and pp represents children with normal eyelids. The genotypic ratio of the woman’s children will be 2:2 or 1:1 and the phenotypic ratio is the same with 2 Ptosis:2 Normal or 1 Ptosis:1 Normal. Therefore, 50% of the children are expected to have ptosis if she marries a man with normal eyelids.

Question 20

In tomatoes, two pairs of genes affect the color of the ripe fruit as follows: R, red flesh, r yellow flesh; Y yellow skin, y colorless skin. Dominance is complete for red flesh and yellow skin. If the genes are independently segregating, calculate the expected phenotypic ratios from the following crosses:
a. a. Rryy x rrYy

give GR and PR

Answer 20

• Genotypic Ratio = 4:4:4:4 or 1:1:1:1
• Phenotypic Ratio = 4:4:4:4 or 1:1:1:1

Question 21

b. RrYY x Rryy

give PR and GR

Answer 21

Therefore;
* Genotypic Ratio = 4:8:4 or 1:2:1
* Phenotypic Ratio = 12:4 or 3:1

Question 22

different alleles are independent of each other in their ___ and ___ patterns

Answer 22

segregation
recombinant patterns

Question 23

are not merely separate elements producing distinct individual effects, but they could also interact with each other giving entirely different phenotypes

Answer 23

Genes

Question 24

may result to modified phenoitypic ratios deviating from those expected of independently assorting gens exhibiting complete dominance

Answer 24

gene interaction

Question 25

heterozygotes are phenotypically identical to the homozygous dominant

Answer 25

complete dominance

Question 26

one gene controlling one trait

Answer 26

allelic interactions

Question 27

f2 phenotypic ratio of complete dominance

Answer 27

3:1

Question 28

heterozygotes are phenotypically intermediate between the two homozygous types

Answer 28

incomplete dominance

Question 29

incomplete dominance f2 phenotype ratio

Answer 29

1:2:1

Question 30

heterozygotes exhibit a mixture of the phenotypic characters of both homozygotes instead of a single intermediate expression

Answer 30

co-dominance

Question 31

expected phenotypic ratio of co-dominance

Answer 31

1:2:1

Question 32

death of the affected individual (homozygous dominant or heterozygous) iccurs after reproduction takes place

Answer 32

dominant lethal

Question 33

dominant lethal f2 phenotypic ratios

Answer 33

0:2:1 or 0:1

Question 34

effects of recessive genes are sufficiently drastic to kill the bearers of certain genotypes

Answer 34

recessive lethal

Question 35

recessive lethal f2 phenotypic ratio

Answer 35

1:2:0 or 3:0

Question 36

two genes controlling one trait

Answer 36

non-allelic interactions

Question 37

an allele of gene masks the effect of the allele of other gene

Answer 37

epistasis

Question 38

complete dominance at both gene pairst but one gene when dominant is epistatic to the other (A is dominant to a: B dominant to b; A epistatic to B and b)

Answer 38

dominant epistasis

Question 39

complete dominance at both gene pairs but the first gene when dominant is epistatic to the second and second gene, when homozygous recessive is epistatic to the first (A dominant to a; B dominant b; A epistatic to B and B; bb epistatic to A_ and aa)

Answer 39

dominant epistasis

Question 40

dominant epistasis f2 expeted PR

Answer 40

12:3:1 or 13:3

Question 40

complete dominance at both gene pairs, but one gene, when homozygous recessive is epistatic or masks the effect of other gene (A dominant to a; B dominant to b; aa epistatic to B and b)

Answer 40

recessive epistasis

Question 41

expected PR of recessive epistasis

Answer 41

9:3:4

Question 42

complete dominance at both gene pairs but either gene, when dominant is epistatic to the other (A dominant to a; B dominant to B; A epistatic to B; B epistatic to a)

Answer 42

duplicate gene action

Question 43

duplicate gene action PR

Answer 43

15:1

Question 44

complete dominance at both gene pairs, but either gene when homozygous recessive is epistatic to the effects of the other gene (A is dominant to al B dominant to b; bb epistatic to A)

Answer 44

complementary gene action

Question 45

complementary gene action PR

Answer 45

9:7

Question 46

complete dominance at both gene pairs, new phenotypes are produced from interaction between dmoninants and between both homozygous recessives (A dominant to a; B dominant to b; a interacts with B)

Answer 46

NOvel phenotypes

Question 47

novel phenotypes PR

Answer 47

9:3:3:1

Question 48

2. What is gene interaction? Differentiate allelic from non-allelic interaction (5 pts).

Answer 48

Gene interaction refers to the phenomenon where the expression of one gene is influenced by the presence or absence of another gene. This interaction can occur between genes located at the same locus (allelic interactions) or at different loci (non-allelic interactions) on chromosomes

Question 49

– occurs between different alleles of a single gene located at the same locus on homologous chromosomes. These interactions can manifest in various forms, including:

Answer 49

allelic interaction

Question 50

– involves genes that are located at different loci, which may be on the same or different chromosomes

Answer 50

non-allelic interactions

Question 51

in which one gene masks or modifies the expression of another gene.

Answer 51

epistasis

Question 52

– in which two or more genes interact to produce a specific phenotype, requiring both to be present for expression.

Answer 52

complementary genes

Question 53

in which, the genes that contribute to the same trait but may have different alleles may affect the outcome.

Answer 53

duplicate genes

Question 54

1. A woman who is blood type A is married to a man who is blood type B. None of the man’s parents are blood type O. This couple has 4 children with the following blood types: O, AB, AB, B. Give the genotypes of the parents.

Answer 54

In summary: * The mother’s genotype is AO. * The father’s genotype is BO.

Question 55

2. Colorblindness in humans is a recessive trait found in the X chromosome. A man and a woman got married and decide to have children. The man is colorblind. a. Can they have a colorblind daughter? What is the probability? Possibility 1: Mother is not colorblind and not a carrier (genotype: XX)

Answer 55

The daughters’ genotypes are both XX’. They are both carriers, but are not colorblind. Therefore, the probability of having a colorblind daughter is 0%. .

Question 56

2. Colorblindness in humans is a recessive trait found in the X chromosome. A man and a woman got married and decide to have children. The man is colorblind. b. Can they have a colorblind son? What is the probability? Possibility 1: Mother is not colorblind and not a carrier (genotype: XX)

Answer 56

he sons’ genotypes are both XY, hence they both have normal vision. Therefore, the probability of having a colorblind son is 0%

Question 57

2. Colorblindness in humans is a recessive trait found in the X chromosome. A man and a woman got married and decide to have children. The man is colorblind. Can they have an offspring who is carrier? What is the probability? What is the gender? Possibility 1: Mother is not colorblind and not a carrier (genotype: XX)

Answer 57

The daughters’ genotypes are both XX’. Having the chromosome carrying the colorblindness gene makes them carriers. Therefore, the probability of having a carrier offspring is 50%; wherein the probability of a carrier offspring for daughters is 100%.

Question 58

Possibility 2: Mother is not colorblind but a carrier (genotype: XX’) 2. Colorblindness in humans is a recessive trait found in the X chromosome. A man and a woman got married and decide to have children. The man is colorblind. a. Can they have a colorblind daughter? What is the probability?

Answer 58

The genotype X’X’ indicates colorblindness. The daughters’ genotypes are XX’ and X’X’, indicating that one may have a normal vision, while the other is colorblind. Therefore, there is a 50% chance of having a colorblind daughter.

Question 59

Possibility 2: Mother is not colorblind but a carrier (genotype: XX’) 2. Colorblindness in humans is a recessive trait found in the X chromosome. A man and a woman got married and decide to have children. The man is colorblind. b. Can they have a colorblind son? What is the probability?

Answer 59

One of their sons exhibit the genotype X’Y; therefore, the probability of having a colorblind son is 50%.

Question 60

Possibility 2: Mother is not colorblind but a carrier (genotype: XX’) 2. Colorblindness in humans is a recessive trait found in the X chromosome. A man and a woman got married and decide to have children. The man is colorblind. b. Can they have an offspring who is carrier? What is the probability? What is the gender?

Answer 60

One of their offspring exhibits the genotype X’X, indicating that while they have normal vision, one of their chromosomes carry the colorblindness gene. Therefore, there is a 25% chance of having a carrier offspring; wherein the probability of a carrier offspring for daughters is 50%.

Question 61

3. When non-allelic genes interact in a way that one of the genes can hide the expression of the other gene, how is it called? Explain.

Answer 61

The terminology where non-allelic genes interact where one of the gene hides the expression of the other gene is epistasis. According to Ostrander (2025), “epistasis is a circumstance where the expression of one gene is modified (e.g., masked, inhibited or suppressed) by the expression of one or more other genes.” This is different from the law of dominance, where the process also involves hiding the expression of the other genes, but with the same genes. This happens because of the interaction of two or more genes at different loci (location on the chromosome) . One gene, the epistatic gene masks the phenotypic expression of another gene, hypostatic gene.

Question 62

4. How do gene interactions affect gene expression?

Answer 62

Gene interactions occur when two or more genes influence a single trait or phenotype. Their products interact, affecting gene expression. Epistasis is the mechanism by which one gene (the epistatic gene) masks or modifies the expression of another gene (the hypostatic gene). If two or more genes are required for a particular function, it is called complementation. However, if either gene has a loss-of-function mutation, the function is disrupted. Sometimes, multiple genes have similar functions. If one gene is inactivated, another can compensate, resulting in an observable phenotypic change.

Question 63

Results of Mendel's crosses in F2 generation when Dominant form = 705 Recessive form = 224

Answer 63

3.15:1

Question 64

Results of Mendel's crosses in F2 generation when Dominant form = 6,022 Recessive form = 2,001

Answer 64

3.01:1

Question 65

genetic makeup of an organism or alleles carried by an individual or arrangement of genes that produces the phenotype

Answer 65

genotype

Question 66

physical characteristic or appearance of an individual

Answer 66

phenotype

Question 67

___ parents can only pass one form of an allele to their ofspring

Answer 67

homozygous

Question 68

___ parents can pass either two forms of an allele to their offspring

Answer 68

heterozygous

Question 69

the general term for an allele that masks the presence of another allele in the phenotype

Answer 69

dominant allele

Question 70

the general term for an allele that is masked in the phenotype by the presence of another allele

Answer 70

recessive allele

Question 71

Mendel went on to examine how the F2 plants passed traits onto successive generations, he found that recessive 1/4 were always true breeding, thus he suggested that there is a 3:1 ratio but it was really a

Answer 71

1:2:1 disguised ratio

Question 72

in a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. All offspring will be hybrid for a trait and will have only the dominant trait express the phenotype. what law

Answer 72

law of dominance

Question 73

check the label for the f1 and f2 generation for the purple petal

Answer 73

+1

Question 74

Mendel was able to understand four things about the nature of heredity: (1) the plants he crossed did not produce progeny of ___ appearance

Answer 74

intermediate

Question 75

Mendel was able to understand four things about the nature of heredity: Mendel learned that for each pair of alternative forms of a character, one alternative was not expressed in the F1 hybrids, but it appeared in some ___ individuals

Answer 75

F2

Question 76

Mendel was able to understand four things about the nature of heredity: The pairs of ___traits examined segregated among the progeny of a particular cross, some individuals exhibiting one trait, some the other

Answer 76

alternative

Question 77

Mendel was able to understand four things about the nature of heredity: These alternative traits were expressed in the F2 generation in the ratio of

Answer 77

3/4 dominant to 1/4 recessive

Question 78

used to show the possible combinations of gametes

Answer 78

Punnett square

Question 79

make a punnett square between Pp and Pp

Answer 79

1 PP 2 Pp 1 pp

Question 80

Mendel's model has five elements: Parents do not transmit physiological traits directly to their offspring. Rather, they transmit discrete information about the traits called ___

Answer 80

factors

Question 81

Mendel's model has five elements: Each individual receives two factors that may code for the same trait or two ___ traits for a character

Answer 81

alternative

Question 82

Mendel's model has five elements: Not all copies of a factor are ___

Answer 82

identical

Question 83

Mendel's model has five elements: The two alleles, one contributed by the male gamete and one by the female do/do not influence each other in any way

Answer 83

do not

Question 84

Mendel's model has five elements: the presence of a particular ___ does not ensure that the trait econded will be expressed in an individual carrying that allele

Answer 84

allele

Question 85

alternative alleles of a character segregate from each other in heterozygous individuals and remain distinct what Mendel's Law of Heredity

Answer 85

Segregation

Question 86

how do we know if it is homozygous (PP) or heterozygous (Pp)?

Answer 86

test cross

Question 87

mating between an individual of unknown genotype and homozygous recessive individual

Answer 87

test cross

Question 88

likelihood that a particular event will occur

Answer 88

probability

Question 89

can be used to predict the outcomes of genetic crosses

Answer 89

principle of probability

Question 90

what is the probability to have each coin landing heads up

Answer 90

1/8

Question 91

find the phenotypes of the F1 in the following crosses. Assume that tall (TT) is dominant to dwarf (tt) TT x TT

Answer 91

GR: 1 PR: 1

Question 92

find the phenotypes of the F1 in the following crosses. Assume that tall (TT) is dominant to dwarf (tt) Tt TT

Answer 92

GR: 2:2 / 1:1 PR: 1 (4 tall)

Question 93

find the phenotypes of the F1 in the following crosses. Assume that tall (TT) is dominant to dwarf (tt) TT x tt

Answer 93

GR 1:1 PR: 1 (4 tall)

Question 94

find the phenotypes of the F1 in the following crosses. Assume that tall (TT) is dominant to dwarf (tt) Tt Tt

Answer 94

GR: 2:1:1 PR: 3:1

Question 95

find the phenotypes of the F1 in the following crosses. Assume that tall (TT) is dominant to dwarf (tt) Tt tt

Answer 95

PR: 2:2/1:1 GC: 2:2/1:1

Question 96

find the phenotypes of the F1 in the following crosses. Assume that tall (TT) is dominant to dwarf (tt) tt tt

Answer 96

GR: 1 PR: 1

Question 97

inheritance of one character is always indepdendent of the inheritance of other characters within the same individual

Answer 97

indepdendent assortment

Question 98

a modern restatement of Mendel's Second Law would be that:

Answer 98

Genes that are located on different chromsomes assort independently during meiosis

Question 99

do a dihybrid cross given SsYy SsYy

Answer 99

GR: 4:2:2:2:2:1:1:1:1 PR 9:3:3:1

Question 100

it states that inheritance of one character is always independent of the inheritance of other characters

Answer 100

law of independent assortment

Question 101

law of independent assortment is based on ___ ___

Answer 101

dihybrid cross

Question 102

genes linked on a chromosome can rearrange themselves through the process of ____

Answer 102

crossing over

Question 103

give the gametes given the parents Tt AA

Answer 103

TA, tA

Question 104

give the gametes BB cc DD

Answer 104

BcD

Question 105

give the gametes Dd EE Aa CC

Answer 105

DEAC DEaC dEAC dEaC

Question 106

allelic interactions

Answer 106

complete dominance incomplete dominance co-dominance dominant lethal recessive lethal

Question 107

non allelic interactions

Answer 107

dominant epistasis recessive epistasis duplicate gene action complementary gene action novel phenotype