Test Bank Flashcards Preview

Plant Genetics and Crop Improvement > Test Bank > Flashcards

Flashcards in Test Bank Deck (42)
Loading flashcards...
1

Inbreeding (self-pollination; sib-mating) results in...

Increased frequency of homozygotes; decreased heterozygosity.

2

Random mating results in...

Genotypic and phenotypic frequencies that are a function of gene frequency.

3

If the broad sense heritability for a trait is 56%, it is known that the contribution of the environment to the total phenotypic variance is...

44%

4

Genetic uniformity among cultivated species (a narrow genetic base) can have a consequence known as...

genetic vulnerability

5

Heritability in the narrow sense is best defined as the...

ratio of additive genetic variance to phenotypic variance.

6

If mass selection for a trait is not effective, that would generally mean that...

the trait has a low heritability.

7

A major advantage of the bulk method of inbreeding a population is that...

natural selection can work to increase the proportion of desirable types.

8

Selection against a recessive allele that is low in frequency in a population in Hardy-Weinberg equilibrium...

is inefficient because most of the alleles are "hiding" in heterozygotes.

9

One of the assumptions underlying the Hardy-Weinberg principle is...

mating is at random.

10

The basic goal of recurrent selection is to...

change the mean in a desirable way while maintaining the degree of genetic variation in population.

11

A type of recurrent selection that would be best suited for traits with low heritability would be...

full-sib recurrent selection.

12

"Gridding" as a concept of recurrent selection as proposed by Burton and others was done primarily to...

reduce environmental variability and bias.

13

The final phase in the development of inbred lines for use in commercial F1 hybrids is...

individual line testing for specific combining ability.

14

Among the following which is the preferred genotype to use as a source of a particular gene, assuming all genotypes are of equal value?

an obsolete cultivar well-adapted to the area, in the same genus and species as the cultivated type.

15

In a population with two alleles, B and b, the frequency of B is 0.43. The frequency of heterozygotes, assuming Hardy-Weinberg equilibrium, would be...

0.49

16

Variance can best be described as...

A measure of the spread of the distribution.

17

A recessive lethal gene can persist for many generations in a population when...

The recessive allele is rare.

18

Mass selection works best with...

traits of high heritability.

19

The phenotypic variance among the F1 generation plants of a cross between two homozygous or inbred lines is assumed to be equal to...

the environmental variance.

20

The ratio of the total genotypic variance to total phenotypic variance is called...

Broad-sense heritability.

21

A heritability estimate of 0.50 means...

50% of the variation in a population is due to environmental factors.

22

A modification of the Bulk Method that overcomes the disadvantage of unintended selection for certain yield components (such as seed size and number) in the Bulk Method is...

Single-seed descent.

23

One advantage of the Pedigree Method of selection is...

it is possible to determine the inheritance or heritability of specific traits.

24

Recurrent selection can be envisioned as a circular process, with an event sequence...

Create population -> evaluate individuals -> intermate the population -> create a population

25

As opposed to other Breeding Methods, Early Generation Testing is primarily concerned with...

Evaluation of Populations rather that individuals within populations.

26

Single-seed descent has one particular advantage over other methods of inbreeding, which is...

It is possible to move through generations rapidly, as many as 3 per year.

27

One reason it is difficult to use recurrent selection in self-pollinated crops is...

It is difficult to achieve the necessary generations of intermating in self-pollinated crops.

28

The overall goal of recurrent selection is to...

Improve the mean performance of a population without a reduction in genetic variance.

29

Phenotypic recurrent selection is best suited for...

Traits with high heritability.

30

A major disadvantage of the backcross method of crop improvement is...

It does not work well with quantitative traits.