Chap 20

Question 1

Height in humans, milk and meat production in cattle, field in various crops are controlled by many ___

Answer 1

Genes

Question 2

This ___ is measured and described in quantitative terms and is known as ____

Answer 2

Continuous variation; quantitative inheritance

Question 3

A continuous quantitative trait is often the results of ___ and is frequently influenced by the ___ or ___

Answer 3

Polygenic inheritance; environment; multifactorial

Question 4

___ is determined by a single gene

Answer 4

Simple trait

Question 5

___ trait determined by two or more genes

Answer 5

Polygenic trait

Question 6

___ trait determined by 2 or more genes +/-environmental contribution

Answer 6

Multifactorial trait

Question 7

___ phenotypes fall into distinct categories (red vs. white)

Answer 7

Discontinuous variation

Question 8

___ phenotypes varies over range, with most falling ~ midway between the extremes

Answer 8

Continuous variation

Question 9

Bateson and Yule proposed the ___ or the ___ in which many genes, each individually behaving in a Mendelian fashion, contribute to the phenotype in a cumulative or quantitative way

Answer 9

Multiple-factor; multiple-gene hypothesis

Question 10

This ___ hypothesis is demonstrated by grain color in wheat to test the concept that the cumulative effects of alleles at multiple loci produce the range of ___ seen in ___ traits.

Answer 10

Multiple-gene; phenotypes; quantitative

Question 11

Each gene has an ___ allele and a ____ allele

Answer 11

Additive; nonadditive

Question 12

The greater the number of ___ alleles in the ___, the more intense the red color expressed in the phenotype

Answer 12

Additive; genotype

Question 13

Each ___ allele contributes equally to pigment in the grain, and the _____ allele failed to contribute to any pigment

Answer 13

Additive; nonadditive

Question 14

What are the multiple-gene hypothesis consists of the following major points?

Answer 14

1. Phenotypic traits show continuous variation that can be quantified by measuring, weighing, etc.
2. Two or more loci show an additive effect on expression of the phenotype and is called polygenic inheritance
3. An additive allele contributes an equal amount to the phenotype, whereas a nonadditive contributes nothing
4. Each additive alleles contribute to a single quantitative trait to produce substantial phenotypic variation
5. The additive alleles contribute to a single quantitative trait to produce substantial phenotypic variation

Question 15

The number of __ contributing to a ___ trait can be estimated based on the ratio of F2 individuals resembling either of the two extreme P1 phenotypes

Answer 15

Polygenes; quantitative

Question 16

For low numbers of ___, the number of ___ loci n can be estimated from the total number of possible ___

Answer 16

Polygenes; additive; phenotypes

Question 17

The estimates of low numbers of Polygenes estimates assume that all of the __ alleles contribute equally and ___. There are no significant environmental effects on ___ expression.

Answer 17

Additive; additively; phenotypic

Question 18

__ traits are usually measured in a sample of individuals that is __ and __ of the population from which it is drawn

Answer 18

Polygenic; large; representative

Question 19

The data often form a ___ distribution that is a characteristic bell-shaped curve when plotted as a frequency histogram

Answer 19

Normal

Question 20

Measurements clustering around a central point called a ____ and the central point is the mean

Answer 20

Central tendency

Question 21

___ is the average of a set of measurements

Answer 21

Mean

Question 22

___ provides information about the spread of data around the mean

Answer 22

Variance

Question 23

If multiple individuals have same measurement, data for each measurement class can be ___

Answer 23

Grouped

Question 24

___ deviation is the square root of the variance

Answer 24

Standard

Question 25

Two phenotypic traits may ___ variation in one trait may be ___ on/associated with variation in a second trait

Answer 25

Correlate; dependent

Question 26

___ is a measurement of how much variation is common to both quantitative traits

Answer 26

Covariance

Question 27

The ___ coefficient indicates to what extent variation in one trait is associated with variation in a second trait

Answer 27

Correlation

Question 28

When r is ___, the two traits both increase or decrease together or one increases as the other decreases when r is ___

Answer 28

Positive; negative

Question 29

___ indicate that an increase in the measure of one traits tends to correlate with an increase in the measure of the second trait

Answer 29

Positive values

Question 30

___ indicate that an increase in one trait tends to be associated with a decrease in the measure of the second trait

Answer 30

Negative values

Question 31

___ described the proportion of total phenotypic variation in a population due to genetic factors

Answer 31

Heritability

Question 32

For a ___ trait, high heritability means most variation is due to ___ factors and less ____ impact

Answer 32

Multifactorial; genetic; environmental

Question 33

With low heritability, environmental factors are likely to have a ___ impact on ___

Answer 33

Greater; phenotype

Question 34

A heritability estimate tells the proportion of ___ variation that can be attributed to ___ variation within a certain population in a particular environment

Answer 34

Phenotypic; genetic

Question 35

Total ___ variance can be divided into ___ variance or ___ variance

Answer 35

Phenotypic; genotypes; environmental

Question 36

When obtaining ___ estimates for multi-factorial traits, researchers often assume that the genotype by environment interaction is small enough to ignore or combine with ___ variance

Answer 36

Heritability; environmental

Question 37

In order to minimize genetic differences between individuals, researchers of tern compare highly inbred ___ and ___ species when estimating heritabilities

Answer 37

Plant; animal

Question 38

Expose different members of the same inbred strain to ___ environments to estimate VE

Answer 38

Different

Question 39

Expose different inbred strains to the ___ environment to estimate VG

Answer 39

Same

Question 40

Broad sense heritability (H2) measure the contribution of the ___ variance to the total ___ variance

Answer 40

Genotypic; phenotypic

Question 41

A value approaching 1.0 indicates that the environment has ___ impact on the ___ variance

Answer 41

Little; phenotypic

Question 42

Low values close to 0.0 indicate that ___ factors, and not the ___ are responsible for ___ variation within a population

Answer 42

Environmental; genotype; phenotypic

Question 43

Estimates of ___ heritability are expressed as percentage values for traits among different ____

Answer 43

Narrow-sense; organisms

Question 44

Narrow-sense heritability more valuable predictor of response to ___

Answer 44

Selection

Question 45

Narrow-sense heritability is the proportion of phenotypic variance due to additive ___ alone

Answer 45

Genotypic variance

Question 46

Narrow-sense heritability estimate are valuable to plant and animal breeders because they estimate the proportion of total ____ variance for that trait that is due to ____ variance

Answer 46

Phenotype; additive genetic

Question 47

It is best to select individuals with superior ___ for the desired ___ trait from a ___ population and to breed offspring from those individuals

Answer 47

Phenotypes; quantitative; heterogeneous

Question 48

Artificial selection: - Choosing specific individuals with ___ from initially ___ population for future breeding - Purpose is to develop population containing high frequency of individuals with ___ traits

Answer 48

Preferred phenotypes; heterogenous; desired

Question 49

Artificial trait selection: - Can be __ and multifactorial - Traits of ___ importance: - crops and livestock - grain yield in plants - weight gain or milk yield in cattle - speed or stamina in horses

Answer 49

Polygenic; economic

Question 50

Realized heritability: - ___ breeding estimate potential success for artificial selection

Answer 50

Selective

Question 51

Heritability values: - Provide no information on genes involved in ___ - Measure in populations- limited application to ___

Answer 51

Traits; individuals

Question 52

Future changes in ___ factors can affect ___

Answer 52

Environmental; heritability

Question 53

Humans twins are useful for examining ___ versus ___ variance for a multifactorial trait

Answer 53

Genotypic; environmental

Question 54

For monozygotic (MZ) or identical twins, ___ variance is due to VE environmental variance, as there is no VG Genotypic variance

Answer 54

Phenotypic

Question 55

For dizygotic (DZ) or fraternal twins, ___ difference represent both environmental variance and approximately half the Genotypic variance

Answer 55

Phenotypic

Question 56

Comparison of phenotypic variances for the same trait in identical and fraternal twin sets provides an estimate of ____ heritability of the Genotypic variance to the total ___ for that trait

Answer 56

Broad-sense; phenotypic

Question 57

The difference in ___ for a given trait in identical versus fraternal twins suggests whether a strong genetic component is involved in ___ of the trait

Answer 57

Concordance; determination

Question 58

Twins are ___ for a trait if both or neither ___ it

Answer 58

Concordant; express

Question 59

If one expresses it and the other does not, the pair is said to be ___ for that trait

Answer 59

Discordant

Question 60

MZ twins are treat more ___ than DZ twins, which may ___ environmental variance among DZ twins

Answer 60

Equally; inflate

Question 61

Interactions between ___ and ___ may produce variability in phenotype, which can ___ total phenotypic variance of DZ twins compared to MZ twins raised in the ___ environment

Answer 61

Genotype; environment; increase; same

Question 62

The assumption that MZ twins share the same ___ has been valuable for estimating heritability for many ___ diseases such as cardiovascular disease, diabetes, mental illness

Answer 62

Genome; multifactorial

Question 63

Results from ___ research has challenged whether MZ twins are truly ___

Answer 63

Genomic; identical

Question 64

Most recent genomic discoveries about identical twins include the following: By the time MZ twins are born, they do no necessarily have identical ___ - they develop from a single egg but become two independent ___ - genotypes can diverge slightly with differences in copy number variation (CNV)- variation in number of copes of numerous large DNA sequences resulting in ___ mosaicism -CNV difference between MZ twins has been associated with ___ lymphoma in one twin but not the other

Answer 64

Genomes; embryos; somatic; chronic

Question 65

Gene-expression patterns in MZ twins change with age, leading to ___ differences - This involves ___- the chemical modification of their DNA and associated histone - MZ. Twins are epigenetically ___ at birth, but adult MZ twins show significant ___ in methylation patterns of both DNA and his tones, which in turn affect gene expression -Progressive age-related genomic ___ may be due to expire to ___ environments or to failure of epigenetic marking following DNA replication

Answer 65

Phenotypic; epigenetics; identical; differences; modifications; different