BIO 202 Chapter 19 Reading Quiz

Based on this diagram and Mendel's laws, what is the percentage of offspring in the F2 generation experiment with yellow peas? a) 25% b) 50% c) 75% d) 100%

75% FEEDBACK: In the F2 generation, there will be 25% YY offspring, 50% Yy(or yY) offspring, and 25% yy offspring. Because the Y (yellow) allele is dominant, both the YY and Yy offspring have yellow peas, so 25% + 50% = 75%.

In the experiment shown below, which SNP is likely linked to the disease allele? a) SNP a b) SNP b c) both SNPs a and b d) neither SNP

SNP a FEEDBACK: By sequencing individuals' DNA to look for SNPs and comparing the SNPs to the occurrence of a disease allele, researchers can map the location of disease-causing genes relative to SNPs.

How does a gain-of-function mutation in Ras promote the development of cancer? a) The mutant Ras inappropriately activates proliferation b) The mutant Ras form aggregates, which interferes with wild-type Ras, causing disease c) Wild-type Ras forms a complex with mutant Ras and leads to uncontrolled gene expression d) Ras is no longer functional, so the cells undergo apoptosis.

The mutant Ras inappropriately activates proliferation FEEDBACK: Mutant gain-of-function Ras is a form that is active without appropriate signals. This active Ras signals inappropriately to proliferation pathways and can lead to uncontrolled cell growth and cancer.

In a complementation test, if two homozygous recessive individuals for a particular phenotype are mated to one another and the offspring show the mutant phenotype, what can you conclude? a) The parents each had mutations in different genes b) You cannot conclude anything c) The parents each had mutations in the same gene d) The offspring are heterozygous

The parents each had mutations in the same gene Feedback: Complementation tests can determine if two recessive mutations are in the same gene. In this test, two homozygous recessive individuals are mated and if their offspring have a wild-type phenotype, the mutations were in different genes, because each individual had a wild-type copy of the other's mutant gene, so they complement each other. If all offspring have the mutant phenotype, the mutations were in the same gene

A gene is the information required to make an RNA or protein product, a(n) ___________ is a variant version of a particular gene. a) allele b) recombinant c) haploid d) homolog

allele FEEDBACK: Alleles are variant versions of a gene; they can code for slightly different products. In sexual reproduction, the maternal and paternal chromosomes each provide one of two different alleles of each gene.

A ___________ is a physical manifestation of a crossover event. a) bivalent b) sister chromatid c) synaptonemal complex d) chiasma

chiasma FEEDBACK: Crossovers are physical exchanges of the DNA strands between homologous chromosomes. These can be seen as a chiasma, where the chromatids cross one another.

Haplotype blocks are combinations of polymorphisms that are inherited as a unit. These occur in the human genome because a) humans have a fast generation time b) the polymorphisms are deleterious c) there is no genome shuffling between generations d) only a few crossovers occur per chromosome

d. only a few crossovers occur per chromosome. FEEDBACK: Haplotype blocks occur because humans evolved from a small population about 2,000 generations ago. Because there are only a few crossovers per chromosome that could separate the polymorphisms, they tend to be inherited as a set through the generations.

Which type of mutation will generally be lost from the population most rapidly? a) recessive/neutral b) dominant/beneficial c) recessive/deleterious d) dominant/deleterious

dominant/deleterious FEEDBACK: Dominant mutations are expressed when present in a single copy. A deleterious mutation that is always expressed will most likely be lost from a population most quickly, because it will exert its negative effects even when a single copy is present in an individual.

A mutation with a small haplotype block surrounding it likely arose a) in the individual being examined b) later in the evolution of the organism c) earlier in the evolution of the organism d) in the previous generation

earlier in the evolution of the organism FEEDBACK: The size of a haplotype block can be used to estimate when a mutation arose in the human population because the older it is, the smaller the haplotype block. This is because the block is more likely to be shuffled and lost by recombination as more generations elapse.

What is the initiating event in meiotic homologous recombination? a) formation of a double-strand break b) strand exchange c) crossing over d) DNA synthesis

formation of a double-strand break FEEDBACK: Crossing over is essentially the repair of an intentional double-strand break by homologous recombination. Recombination can lead to strand exchange and crossover events.

A bivalent contains ___________ sister chromatids a) one b) two c) eight d) four

four FEEDBACK: A bivalent is a structure composed of two duplicated homologous chromosomes. Because each duplicated chromosome has two sister chromatids, the bivalent contains four sister chromatids.

When an organism has inherited two nonidentical alleles, it is said to be a) dominant b) heterozygous c) recessive d) homozygous.

heterogygous FEEDBACK: An organism with two dissimilar alleles for a gene is said to be heterozygous for that gene.

Which of the following contribute to genetic reassortment during meiosis? a) homologous recombination in meiosis II b) crossing-over of chromosomes during meiosis I c) independent assortment in meiosis I d) independent assortment and crossing-over during meiosis I

independent assortment and crossing-over during meiosis I FEEDBACK: Meiosis produces haploid gametes from diploid cells, shuffling the genetic information in the process; this is called genetic reassortment. The chromosomes are independently assorted to different daughter cells, and crossing-over events shuffle the genetic information between maternal and paternal chromosomes.

The kinetochores of sister chromatids in meiosis I attach to a) microtubules from the spindle poles in a random fashion b) microtubules from the same spindle pole c) microtubules from opposite spindle poles d) Only one kinetochore attaches to microtubules.

microtubules from the same spindle pole FEEDBACK: In meiosis I, the homologous chromosomes are separated from each other, but sister chromatids segregate to the same daughter cell. The kinetochores of the sister chromatids both attach to microtubules from the same spindle pole, so that they can be moved to the same pole during the first meiotic division.

The four products of human germ-cell meiosis each contain ___________ copy(ies) of each gene. a) two b) four c) one d) eight

one FEEDBACK: Meiotic division of a diploid produces four haploid products. The germ cells begin as diploid, but the first division reduces the number of chromosomes by half, so that each cell contains just one copy of each gene.

The set of traits of an organism that are determined by the genetic makeup is referred to as the a) genotype. b) haplotype. c) flavor. d) phenotype.

phenotype FEEDBACK: The genotype is the genetic makeup (the DNA sequence of genes) in an organism. The phenotype is the outward appearance or traits, which are influenced by the genotype of the organism.

The most common types of polymorphisms in the human genome are a) indels b) aneuploidies c) copy-number variants d) single-nucleotide polymorphisms

single-nucleotide polymorphisms. FEEDBACK: The human genome sequence varies from individual to individual, with common variations that are called polymorphisms. The most common polymorphism is a single nucleotide change, or single-nucleotide polymorphism (SNP).

A loss-of-function mutant will always be dominant if a) the mutant protein is expressed at wild-type levels b) the normal gene product can compensate for the loss of function product c) the mutant form of the protein is rapidly degraded d) the mutant form of the protein interferes with the wild-type version.

the mutant form of the protein interferes with the wild-type version. FEEDBACK: Loss-of-function mutations are often recessive because the wild-type allele can make gene product that compensates for the mutant allele. However, a loss-of-function mutant will be dominant if it interferes with the function of the wild-type allele.

If an organism, when allowed to self-fertilize, produces offspring with the same traits it is called a) inherited b) true breeding c) phenotype d) inbreeding.

true breeding

Classical genetic approaches to studying gene activity include all of the following EXCEPT a) identifying naturally occurring mutant organisms with phenotypes of interest b) using CRISPR to knock out a gene of interest c) using genetic screens for conditional mutants d) mutagenizing organisms and isolating mutants with a desired phenotype.

using CRISPR to knock out a gene of interest FEEDBACK: Classical genetic approaches involve identifying or isolating mutant organisms with a phenotype that represents the loss of function of the cellular process of interest. The genes that are mutated are then identified to determine which genes are required for that process.