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Genetics - BI 312 > Chapter 3: Basic Principles of Heredity > Flashcards

Chapter 3: Basic Principles of Heredity Flashcards

1
Q

What is Mendel’s first law?

A

The alleles of genes (in diploids) segregate equally into gametes

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2
Q

What is Mendel’s 2nd law?

A

Different genes assort independently in meiosis.

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3
Q

What are some traits of X-linked dominant genes

A
  1. Affected males transfer to all daughters
  2. Affected females transfer to half of their offspring
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4
Q

Define gene

A

An inherited factor that determines a characteristic

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5
Q

Define allele

A

Different versions of genes

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6
Q

Define locus

A

The location of particular alleles

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7
Q

Define genoty[e

A

The set of alleles that an individual organism possesses

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8
Q

Define homozygous

A

A genotype consisting of two identical alleles

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9
Q

Define heterozygous

A

A genotype consisting of two different alleles

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10
Q

Define phenotype

A

The appearance of a characteristic

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11
Q

Which factors did not contribute to Mendel’s success in his heredity study?

a) His use of the pea plant
b) His study of plant chromosomes
c) His adoption of an experimental approach
d) His use of mathematics

A

b) His study of plant chromosomes

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12
Q

What is the difference between a locus and an allele? What is the difference between a phenotype and a phenotype?

A

A locus is a place on a chromosome where genetic information encodes a characteristic.

An allele is a version of a gene that encodes a specific trait.

A genotype is the set of alleles possessed by an individual organism

A phenotype is the manifestation or appearance of a characteristic

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13
Q

Define monohybrid crosses

A

Crosses between parents that differed in a singly characteristic

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14
Q

Define parental generation (P generation)

A

The first generation of a cross

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15
Q

Define F1 generation (first filial generation)

A

The offspring of the P generation

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16
Q

Define reciprocal crosses

A

Taking a strain from one parent and testing it in another cross

EX:

Men performed a reciprocal cross. In one cross, pollen (the male gamete) was taken from a plant with round seeds, and in its reciprocal cross, pollen was taken from a plant with wrinkled seeds. Reciprocal crosses gave the same result; all F1 seeds were round.

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17
Q

Define F2 generation (second filial)

A

The offspring of the F1 generation

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18
Q

Define dominant

A

Traits that appear unchanged between generations

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19
Q

Define recessive

A

Traits that disappear over generations

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20
Q

Define the principle of segregation (Mendel’s first law)

A

Each diploid organism possesses two alleles for any particular characteristic, one inherited from the maternal parents and one from the paternal parent.

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21
Q

Define the concept of dominance.

A

When two different alleles are present in a genotype, only the trait encoded by one of them is the dominant allele- is observed in the phenotype.

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22
Q

How did Mendel know that each of his pea plants carried two alleles encoding a characteristic?

A

The traits encoded by both alleles appeared in the F2 progeny

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23
Q

Define chromosome theory of heredity.

A

The theory that genes are located on chromosomes

24
Q

Define backcross

A

A cross between the F1 generation and its parental generation

25
Q

Define punnett square

A

An image that is made by drawing a grid, listing the gametes produced by one parent along the upper edge and listing the gametes produced by the other parent down the left side.

26
Q

Define probability

A

An expression of the likelihood of the occurrences of a particular event

27
Q

Define multiplication rule

A

The probability of two or more independent events taking place together is calculated by multiplying their independent probabilities.

Ex:

1/4 * 1/4 = 1/16

28
Q

Define addition rule

A

The probability of any two or more mutually exclusive events taking place is calculated by adding the probabilities of the events.

Ex: 1/6 + 1/6 = 2/6 (or simplified, 1/3)

29
Q

If the probability of being blood type A is 1/8 and the probability of being blood type O is 1/2, what is the probability of being either blood type A or blood type O

a) 5/8
b) 1/2
c)1/10
d)1/16

A

a) 5/8

30
Q

Define conditional probability

A

When there is additional information that modifies the probability of a situation

31
Q

Define testcross

A

A useful tool for analyzing genetic crosses where one individual of unknown genotype is crossed with another individual with a homozygous recessive genotype for the trait in question

32
Q

Define wild type

A

The most common allele for a characteristic

33
Q

Define dihybrid cross

A

Crossing of organisms with differences in two categories rather than one

34
Q

Define the principle of independent assortment (Mendel’s 2nd law)

A

Alleles at different loci separate independently of one another

35
Q

How are the principles of segregation and independent assortment related, and how are they different?

A

Both the principle of segregation and the principle of independent assortment refer to the separation of alleles in anahase I of meiosis. The principle of segregation says that these alleles separate, and the principle of independent assortment says that they separate independently of alleles at other loci.

36
Q

Define chi-square goodness-of-fit test

A

A statistical test used to evaluate the role of chance in producing deviations between observed and expected values

37
Q

A chi-square test comparing observed and expected numbers of progeny is carried out, and the probability associated with the calculated chi-square value is 0.72. What does this probability represent?

a) Probability that the correct results were obtained
b) Probability of obtaining the observed numbers
c) Probability that the difference between observed and expected numbers is significant
d) Probability that the difference between observed and expected numbers could be due to chance

A

d) Probability that the difference between observed and expected numbers could be due to chance

38
Q

Define pedigree

A

A pictorial representation of a family history

39
Q

Define proband

A

The person from whom the pedigree initiated from

40
Q

Define consanguinity

A

Mating between closely related people (incest)

41
Q

Recessive traits often appear in pedigrees in which there have been consanguineous mating because these traits…

a) tend to skip generations
b) appear only when both parents carry a copy of the gene for the trait, which is more likely when the parents are related
c) usually arise in children born to parents who are unaffected
d) appear equally in males and females

A

b) appear only when both parents carry a copy of the gene for the trait, which is more likely when the parents are related

42
Q

Of the following ideas postulated by Gregor Mendel, which one requires at least two genes to be demonstrated?

a) Genes assort independently in humans
b) One of two alleles from each parent is randomly transmitted to offspring
c) Traits are not determined by blending
d) Some alleles are recessive and are masked by dominant alleles
e) Traits are controlled by discrete units

A

a) Genes assort independently in humans

43
Q

How is a true breeding purple-flowered pea plant different from a hybrid purple-flowered pea plant?

a) They have the same genotype but different phenotypes
b) They have the same genotype and phenotype
c) They have a different genotype and phenotype
d) They have the same phenotype but different genotypes

A

d) They have the same phenotype but different genotypes

44
Q

In pea plants, plant height is ocntrolled by a single autosomal dominant gene. Tall plants (H) are dominant to short plants (h).

In a cross of two heterozygous plants, which phenotype ratio is expected from the resulting offspring?

a) 1:2:1
b) 1:1
c) 9:3:3:1
d) 3:1

A

d) 3:1

45
Q

At times in the past, red hair in humans was thought to be a recessive trait, and at other times it was thought to be a dominant trait.

  1. What feature of inheritance would red hair be expected to exhibit if it were a RECESSIVE trait?

a) two red-haired parents could have children without red hair
b) two red-haired parents will only have children with red hair
c) affects males and females differently

  1. What feature of inheritance would red hair be expected to exhibit if it were a dominant trait?

a) Two red-haired parents could have children without red hair
b) affects males and females different
c) two red-haired parents will only have children with red hair

A

1: b) two red-haired parents will only have children with red hair

2: a) Two red-haired parents could have children without red hair

46
Q

In humans, oculocutaneous (OCA) albinism is a collection of autosomal recessive disorders characterized by an absence of the pigment melanin in skin, hair, and eyes. That is, normal pigmentation (A) is dominant over albino characteristics (a). For this question, assume the phenotype is determined by a single gene with two alleles

If both parents have normal pigmentation, what are all the possible genotypes that may be observed in their offspring?

a) AA or Aa only
b) Aa only
c) AA, Aa, or aa
d) aa only

A

c) AA, Aa, or aa

47
Q

Suppose there is a vial containing a single generation of flies from a cross. There is an interesting phenotype where many individuals have abnormally long hairlike bristles, sensory organs extending from the dorsal thorax, as opposed to the short wirelike wild-type bristles among other siblings. References state that this mutant has a dominant mutation called Suave (Su) and that the phenotype of flies that are heterozygotes or homozygotes for Su appear phenotypically identical.

Which fly should be crossed to a Suave male from this vial in order to generate progeny that helps determine the male’s genotype?

a) a Suave female sibling
b) a wild-type sibling
c) a female mutant for another unknown bristle mutation
d) none of the above

A

b) a wild-type sibling

48
Q

In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2.

What will be the phenotypic ratio in the F2?

a) All sweet fruit with no spots
b) All bitter fruit with yellow spots
c) 9/16 bitter fruit-yellow spots; 3/16, bitter fruit-no spots; 3/16 sweet fruit-yellow spots; and 1/16 sweet fruit-no spots
d) 1/2 bitter fruit-yellow spots and 1/2 sweet fruit-no spots
e) 1/4 itter fruit-yellow spots; 1/4 bitter fruit-no spts, 1/4 sweet fruit-yellow spots, 1/4 sweet fruit-no spots

A

c) 9/16 bitter fruit-yellow spots; 3/16, bitter fruit-no spots; 3/16 sweet fruit-yellow spots; and 1/16 sweet fruit-no spots

49
Q

In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2.

If an F1 plant is backcrossed with the bitter yellow-spotted parent, what phenotypes and proportions are expected in the offspring?

a) 1/4 bitter fruit-yellow spots, 1/4 bitter fruit-no spots, 1/4 sweet fruit-yellow spots, 1/4 sweet fruit-no spots
b) All bitter fruit with yellow spots
c) All sweet fruit with no spots
d) 1/2 bitter fruit-yellow spots; 1/2 sweet fruit-no spots
e) 9/16 bitter fruit-yellow spots; 3/16, bitter fruit-no spots; 3/16 sweet fruit-yellow spots; and 1/16 sweet fruit-no spots

A

b) All bitter fruit with yellow spots

50
Q

In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2.

If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and proportions are expected in the offspring?

a) All bitter fruit with yellow spots
b) 1/4 itter fruit-yellow spots; 1/4 bitter fruit-no spts, 1/4 sweet fruit-yellow spots, 1/4 sweet fruit-no spots
c) 1/2 bitter fruit-yellow spots; 1/2 sweet fruit-no spots
d) 9/16 bitter fruit-yellow spots; 3/16, bitter fruit-no spots; 3/16 sweet fruit-yellow spots; and 1/16 sweet fruit-no spots
e) All sweet with no spots

A

b) 1/4 itter fruit-yellow spots; 1/4 bitter fruit-no spts, 1/4 sweet fruit-yellow spots, 1/4 sweet fruit-no spots

51
Q

Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU.

What is the probability that a sperm from the father will contain the PKU allele?

a) 1/3
b) 1/2
c) 3/4
d) 2/3
e) 1/4

A

b) 1/2

52
Q

Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU.

What is the probability that an egg from the mother will contain the PKU allele?

a) 1/3
b) 2/3
c) 1/4
d) 3/4
e) 1/2

A

e) 1/2

53
Q

Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU.

What is the probability that their next child will have PKU?

a) 1/2
b) 2/3
c) 1/3
d) 1/4
e) 3/4

A

d) 1/4

54
Q

Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU.

What is the probability that their next child will be heterozygous for the PKU gene?

a) 2/3
b) 1/3
c) 1/4
d) 1/2
e) 3/4

A

d) 1/2

55
Q

In a hypothetical mouse species, brown fur (B) is completely dominant to white fur (b), and long fur (L) is completely dominant to short fur (l)

If two heterozygous mice mate and produce a litter of pups, what is the probability that an individual pup will have brown, short fur?

a) 1/16
b) 9/16
c) 3/4
d) 3/16
e) 1/4

A

d) 3/16

56
Q

Suppose Pablo breeds flowers and wants to optimize the production of offspring with both short stems and white flowers, which are coded for by two genes with the recessive alleles t and p, respectively. In flowers, T codes for tall stems, and P codes for purple flowers. Pablo crosses two heterozygotes that produce 752 offspring.

How many of the 752 offspring are predicted to have both short stems and white flowers?

A

47

Genetics - BI 312 (11 decks)

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