Genetics - Chapter 5

​The correlation coefficient for unrelated people is _______

0

What would be the best way to determine phenotypic variation when only two genes are involved in controlling a trait?

Counting

Using today's genetic technology, it is possible to select _______ for specific traits.

Embryos

_______ traits are controlled by two or more genes and significant environmental interactions.

Multifactorial

Along with a significant genetic component, _________ plays a significant role in the development of spina bifida.

Nutrition

Dizygotic twins are no more or less genetically similar than are other pairs of ______

Siblings

The effect of each dominant allele of a complex trait ________ is and _________.

Small, additive

​Heritability studies cannot provide information about the number, location, or identity of genes involved in specific complex traits.

True

regression to the mean

averages out phenotypic extremes

Twins are concordant for a trait when ____. a. only identical twins have the trait b. only fraternal twins have the trait c. both twins have the trait d. all of the twins' siblings have the trait e. both twins share the trait with at least one parent

c. both twins have the trait

In humans, skin color is a(n) ________ as genes control the amount, type and distributions of the pigment melanin in skin. These variations are believed to represent adaptations to the intensity and ultraviolet nature of sunlight.

multifactorial complex trait

genetic variance

phenotypic variation derived from the different genotypes in a population

recurrence risk

the chance that parents will have a second or third affected child because their genotypes are close to the threshold level

monozygotic

the fertilization of a single egg and a single sperm that gives rise to twins

Another distinguishing characteristic is that two or more genes contribute to the phenotype. How does this occur?

All genes contribute to the phenotype

A complex trait is controlled by one gene.

False

An individual's phenotype is fixed at the moment of fertilization and barring mutation is unchanging.

False

Epigenetics describes the concept that each individual's genotype is determined at the time of fertilization.

False

Genes discovered to date that control height account for about 75% of the total variation in adult height which explains most of the observed variation.

False

Genes exist and operate in an environment that includes all the other genes in the genotype, their effects and interactions, but does not include the influence of non-genetic factors.

False

Human height is not a multifactorial complex trait.

False

Human skin color is determined by a single gene, which controls the amount of melanin in the skin.

False

Monozygotic twins separated at birth share different genotypes as well as different environments.

False

Only some of the many genes that control human skin color actually contribute to the phenotype.

False

Phenotypic variation is derived from three sources: different genotypes present in the population, different genotypes present between populations and different environments in which identical genotypes are expressed.

False

Studies of various human races have revealed a heritability value of 1.0 for human intelligence.

False

The additive model for polygenic inheritance proposes that the genes controlling a trait are all on one chromosome.

False

The degree of difference in concordance between MZ and DZ twins is important; the greater the difference the lesser the heritability.

False

The genotype is variable and undergoes continuous change throughout the life of the organism.

False

The regression to the mean describes the contribution of environmental factors to polygenic phenotypes.

False

​The hormone leptin is produced by ______ cells.

Fat

Complex traits are usually quantified by _______ rather than by ________.

Measurement, counting

What would be the best way to determine phenotypic variation when four or more genes control a trait?

Measuring

Phenotypic expression varies widely. This variation is best analyzed in ______

Populations

Complex traits have several distinguishing characteristics. What is one of these?

Traits are quantified by measurememnt

A heritability value of 1.0 for a given complex trait in the human population indicates that phenotypic variations are due solely to genetic variance.

True

As the degree of relatedness increases, the probability that individuals will have the same combination of alleles that controls the trait increases.

True

Examining the amount of phenotypic variation in a population rather than among individuals enables geneticists to measure the interaction between the genotype and the environment.

True

Gene-wide association studies reveal that if a gene which may be controlling a specific trait is near the chromosome location of these SNPs, the candidate gene near the SNPs can be investigated to see how it contributes to the complex trait.

True

Heritability estimates are determined at the phenotypic level and cannot tell us anything about how many genes control the trait being studied, whether the genes are inherited in a dominant, recessive, or sex-linked pattern, or how the genes act together to produce the phenotype.

True

Human height is a complex trait, controlled by both genetic and environmental factors.

True

If a child has a severe spina bifida phenotype, there is a greater risk that a sibling with the same parents will also have spina bifida.

True

In complex traits, each gene contributes additively to the phenotype.

True

In genomic-wide association studies, researchers use up to half a million SNPs to scan tens of thousands of genomes to see whether a particular halotype is found significantly more often in one group of people than another.

True

King Frederick William's human breeding program failed, indicating that human height is probably a complex genetic trait.

True

MZ twins can have different phenotypes due to epigenetic interaction.

True

Measuring heritability gives an estimate of the genotypic contribution to the phenotype of complex traits.

True

Some human complex traits include skin color and intelligence.

True

The concordance values for blood type for monozygotic and dizygotic twins are 100% and 66%, respectively; therefore, environmental factors do not influence blood type in humans.

True

The pea traits that Mendel studied exhibited discontinuous variation.

True

The phenotype is the sum of the observable characteristics.

True

The risk for some genetic disorders and congenital malformations declines as the degree of relatedness between affected individuals declines.

True

​Continuous phenotypic variations can be explained by Mendelian inheritance.

True

​Dizygotic twins originate from two separate fertilization events.

True

​For threshold traits, the liability for a genetic disorder is distributed among individuals in a bell-shaped curve.

True

leptin

a hormone produced by fat cells that interacts with the hypothalamus

frequency distribution

a means of showing the number of categories in which a variable can appear, as well as the number occurring in each category

Complex traits are characterized by phenotypes that ________. a. are quantified rather than counted b. have two distinct variations c. are typically studied in individuals, not populations d. are not controlled by environmental factors e. are determined by only one gene

a. are quantified rather than counted

The median heritability values for IQ for monozygotic twins reared together vs. monozygotic twins reared apart are estimated at 0.85 and 0.68, respectively. From this information, we can conclude ________. a. environmental influences help determine phenotypic variation of IQ in human populations b. monozygotic twins reared together always have a higher general cognitive ability than those reared apart c. studying SNP differences in monozygotic twins can reveal genes involved in determining human intelligence d. monozygotic twins reared together have higher IQs than those reared apart e. these values are expected to have stayed the same, from the early 1900s to today

a. environmental influences help determine phenotypic variation of IQ in human populations

A trait with a heritability value of 0.75 indicates that 75% of the phenotypic variability seen in the population is caused by ____ of the population. a. genetic differences b. ​epigenetic effects c. the equal contribution of the genotype and the environment d. concordance e. environmental differences

a. genetic differences

complex traits

are traits controlled by multiple factors

additive model

assumes that each gene involved has an equal and additive affect on the phenotype

Twin, adoption, and family studies show that obesity has a heritability that averages close to ____. a. 0.3 b. 0.7 c. 0.1 d. 0.9 e. 0.5

b. 0.7

Suppose a trait is determined by five different genes. You can assume that ________. a. environmental factors will have a lesser effect on phenotype than each individual gene involved b. environmental factors will have a greater effect on the phenotype than each individual gene involved c. this is not a complex trait d. this trait exhibits discontinuous distribution e. there are sixteen different combinations of dominant and recessive alleles that control phenotype variation

b. environmental factors will have a greater effect on the phenotype than each individual gene involved

Cleft palate is ____.​ a. only transmitted from father to son b. explained by the threshold model of complex traits c. controlled by a single gene pair d. controlled only by genetics e. a continuously distributed trait

b. explained by the threshold model of complex traits

Spina bifida is one of the most common and most complex birth defects involving the ____ system. a. digestive b. nervous c. endocrine d. circulatory e. respiratory

b. nervous

Consider a scenario in which a group of genetically identical mice are split into two different cages. The mice in one cage are fed a high sugar diet and become obese; the mice in the second cage are fed a normal diet and maintain normal weight. Based on this information, the ________. a. heritability value for phenotypic variations in weight is 1.0 b. phenotypic variations in weight are due to 100% environmental variance c. heritability value for phenotypic variations in weight is 0.5 d. correlation coefficient of the mice is 0 e. phenotypic variations in weight are due to 100% genetic variance

b. phenotypic variations in weight are due to 100% environmental variance

The heritability of a trait is the ____. a. average amount of genetic variation in each individual b. proportion of phenotypic variation that is caused by different genotypes c. ​sum of all phenotypic variation in a population d. proportion of phenotypic variation that is caused by the environment e. absolute measurement of genotypic variation in a population

b. proportion of phenotypic variation that is caused by different genotypes

Suppose scientists discover a particular haplotype present in tall individuals. This observation would suggest that ________. a. only individuals with this haplotype will be tall b. there is no genetic contribution to the trait of human height c. a gene or genes near the chromosomal locus of the haplotype may control human height d. tall parents always have tall children e. these individuals are homozygous for the HMGA2 gene

c. a gene or genes near the chromosomal locus of the haplotype may control human height

Because three human genes − TYR, SLC45A, and SLC24A5 − contribute the most to darker human skin color, we can assume that ________. a. two individuals − one with a homozygous dominant and the other with a homozygous recessive genotype for these genes − will tend to have children who are dark-skinned b. human skin color is controlled only by these three genes c. individuals who have homozygous dominant genotypes for these three genes probably live near the equator d. environmental factors do not contribute to human skin color e. individuals who have homozygous dominant alleles for these three genes probably live at high latitudes

c. individuals who have homozygous dominant genotypes for these three genes probably live near the equator

During interaction between genes and environment, the phenotype ____. a. is expressed as discontinuous variation b. can be quantitatively subdivided into genotypic and environmental components c. is variable and undergoes continuous change throughout the life of the organism d. cannot vary e. changes the genotype

c. is variable and undergoes continuous change throughout the life of the organism

The concept of ____ explains why children of parents who are at the extreme ends of a normal (bell-curve) distribution for a phenotype are usually closer to the population average for the phenotype. a. concordance b. correlation coefficient c. regression to the mean d. ​multifactorial differences e. epigenetics

c. regression to the mean

Human body weight shows overlapping phenotypes, indicating that this trait ________. a. shows discontinuous variation b. cannot be multifactorial c. shows continuous variation d. cannot be polygenic e. is a monogenic trait

c. shows continuous variation

discontinuous variation

can be counted because phenotypes fall into two or more distinct non-overlapping classes

continuous variation

can be measured because phenotypes show a range of distribution

epigenetics

chemical modifications that selectively turn different gene sets and off

polygenic traits

controlled by two or more genes

multifactorial traits

controlled by two or more genes and the interaction of one or more environmental factors

According to Wilhelm Stern's method of measurement, a ten-year-old child who is able to perform the mental tasks of a ten-year-old (but not of an eleven-year old) has an IQ of ____. a. ​110 b. 90 c. 80 d. 100 e. 120

d. 100

How does the concept of regression to the mean explain why tall parents do not always produce tall offspring? a. Tall parents are usually tall due to hormonal imbalances. b. Short parents tend to have children who are shorter than average. c. Only a few genotype combinations are possible when mating a tall man with a tall woman. d. Tall parents tend to have children of average height. e. Tall parents tend to have children who are taller than average.

d. Tall parents tend to have children of average height.

The ____ model of genetic analysis of complex traits assumes that each gene involved has an equal effect on the phenotype. a. cumulative b. epigenetic c. phenotypic d. additive e. polygenic

d. additive

Genetic testing for complex traits ____. a. reveals the effects of the environment on the genome b. does not supply enough information to make it useful c. reveals how many genes are involved in producing the trait d. cannot exactly define risks e. reveals the phenotype of the organism

d. cannot exactly define risks

According to the additive model of complex traits, ________. a. hormonal imbalances contribute more to phenotype than genetic factors b. each gene has varying effects on phenotype c. tall parents will typically produce short children d. each gene has an equal and additive effect on phenotype e. short parents will typically produce tall children

d. each gene has an equal and additive effect on phenotype

Mendel's pea plants made good experimental subjects because they ____. a. exhibit continuous variation b. are sterile c. exhibit a variety of inheritance patterns d. exhibit discontinuous variation and complete dominance e. have many complex traits that are easy to research

d. exhibit discontinuous variation and complete dominance

Diabetes is a discontinuous trait that is determined by both genetic and environmental factors. When enough of these factors are present, the condition is expressed. Based on this information, the expression of diabetes ________. a. cannot be predicted by analyzing the risk of recurrence in an affected family b. is due solely to epigenetics c. will not be observed in future children of families with affected children d. exhibits a threshold effect e. is seen only in cases of parental consanguinity

d. exhibits a threshold effect

Genomic technology allows researchers to use ____ to survey the genome to detect associations between common variations and a specific phenotype. a. chromosome number b. ​RNA c. continuous traits d. nucleotide variations e. pedigrees

d. nucleotide variations

If we assume that the heritability values for obesity in humans is approximately 0.70, then we can also assume that ________. a. phenotypic variation in weight is due to genetic factors alone b. obesity-related genes identified by GWAS have large additive effects on the phenotypic variation in weight c. the concordance value for monozygotic twins will always be double that for dizygotic twins d. phenotypic variation in weight is due to both genetic and environmental factors e. humans who have the ob and db genes do not produce leptin

d. phenotypic variation in weight is due to both genetic and environmental factors

Most evidence indicates that skin color is controlled by ____ gene pair(s). a. two to three b. fifteen c. five to seven d. ten e. one

d. ten

King Frederick William of Prussia used selective breeding to produce tall soldiers for his Potsdam Grenadier Guards. Why did this breeding program fail? a. Tall men were selected to breed with short women. b. Genetic counseling was not available in the 1700s. c. Human height is a dominant trait. d. Human height follows the same Mendelian rules as plant height in peas. e. Human height is a complex trait.

e. Human height is a complex trait.

In monozygotic twins, the concordance value for handedness is 79%; in dizygotic twins, the value is 77%. This information suggests ________. a. a high genetic contribution to the phenotypic variation observed in handedness in humans b. both monozygotic and dizygotic twins have identical genotypes c. both monozygotic and dizygotic twins share approximately 75% of their genes d. the monozygotic twins in this study were separated at birth and reared in different adoptive environments e. a high environmental contribution to the phenotypic variation observed in handedness in humans

e. a high environmental contribution to the phenotypic variation observed in handedness in humans

The tall and short phenotypes in pea plants are examples of ____. a. multifactorial traits b. continuous traits c. gene interaction d. polygenic traits e. discontinuous traits

e. discontinuous traits

The science of epigenetics seeks to explain ________. a. the contribution of each gene to the phenotype in complex traits b. how maternal and paternal genes contribute to the genotype of the offspring c. the presence of permanent chemical modifications to DNA and histones d. how DNA mutations after fertilization alter gene expression patterns e. how gene expression patterns differ due to environmental factors

e. how gene expression patterns differ due to environmental factors

Human eye color is determined by at least three different genes, which produce phenotypic variation (many colors) in the human population. Therefore, this trait ________. a. has discontinuous variation b. is monogenic c. does not show Mendelian inheritance patterns d. is multifactorial e. is polygenic

e. is polygenic

One characteristic of continuous variation is that ____. a. traits are usually quantified by counting b. individual genes have a large effect on the phenotype c. it is best analyzed in individuals rather than in populations d. only a single gene pair contributes to the phenotype e. phenotypic expression varies across a wide range

e. phenotypic expression varies across a wide range

threshold model

explains the discontinuous distribution of some complex traits; above a specific level, an individual will be affected

An expanded definition of intelligence that goes beyond IQ is called ________ and includes verbal and spatial abilities, memory, speed of perception, and reasoning.

general cognitive ability

Similarities in IQ in MZ twins (who share 100% of their genes) and among children who are siblings and raised in the same family indicates the role that _______ in the role of intelligence.

genetics

correlation coefficient

the measure that determines the degree to which two variable's movements are associated

dizyogtic

the nearly simultaneous fertilization of two eggs and two sperm giving rise to twins

environmental variance

the phenotypic variation seen among individuals with the same genotype

genetic liability

the possibility that the predisposition for a genetic disorder is high enough that if exposed to the proper environmental conditions an individual will develop this disorder

concordance

the probability that a pair of individuals will both have a certain trait

heritability

the proportion of observed variation that is caused by differences in genotypes