BIO UNIT 4 QUIZ

In Drosophila, the allele red eyes (bw+) is dominant to the allele for brown eyes (bw). At another gene locus on the same chromosome, the allele for thin wing veins (hv+) is dominant to the allele for heavy wing veins (hv). Flies homozygous for bw and hv+ are crossed to flies homozygous for bw+ and hv to obtain doubly heterozygous F1 progeny. What would be the results of a test cross with the F1 flies?

1 brown eye, thin wing veins: 1 red eye, heavy wing veins

In Drosophila, the allele red eyes (bw+) is dominant to the allele for brown eyes (bw). At another gene locus on the same chromosome, the allele for thin wing veins (hv+) is dominant to the allele for heavy wing veins (hv). Flies homozygous for bw and hv+ are crossed to flies homozygous for bw+ and hv to obtain doubly heterozygous F1 progeny. Given that these two gene loci are very closely linked, the phenotypic ratio in the F2 generation should be closest to

1 brown eye, thin wing veins: 2 red eye, thin wing veins: 1 red eye, heavy wing veins

In humans, the sickle-cell trait is caused by a single defective allele, but sickle-cell disease only occurs in individuals that are homozygous for the sickle-cell allele. A man and woman each carry the trait, but do not have sickle-cell disease. What is the probability that their first two children will both have sickle-cell disease?

1/16

Meiosis results in a reassortment of maternal chromosomes (inherited from the mother) and paternal chromosomes (inherited from the father). If n=4 for a given species, and ignoring the effects of crossing over, what is the probability that a gamete will receive only paternal chromosomes?

1/16

Let Y = yellow and y = green, and R = round and r = wrinkled. You cross YYRR peas with yyrr peas. All of the F1 individuals are yellow and round with a genotype of YyRr. You then perform an F2 cross and get the expected 9:3:3:1 phenotypic ratio. What proportion of the F2 plants are expected to be heterozygous for both traits?

1/4

A secretor (allele seS) is a person who secretes their blood type antigens into body fluids such as saliva. By comparison, a non-secretor (allele seNS) does not. A person's status as a secretor or non-secretor is independent of blood type. Consider the following inheritance pattern of this trait: The genotypic ratio produced in the last cross is most likely

1:2:1

In Drosophila, the allele red eyes (bw+) is dominant to the allele for brown eyes (bw). At another gene locus on the same chromosome, the allele for thin wing veins (hv+) is dominant to the allele for heavy wing veins (hv). Flies homozygous for bw and hv+ are crossed to flies homozygous for bw+ and hv to obtain doubly heterozygous F1 progeny. Given that these two gene loci are very closely linked, the genotypic ratio in the F2 generation should be closest to

1:2:1

Let P = purple flowers and p = white, and T = tall plants and t = dwarf. Of the 16 possible gamete combinations in the dihybrid cross between 2 double heterozygotes, how many would produce the phenotype white, tall?

3

A male fruit fly has the genotype PpYYrrTt. In terms of these 4 allele pairs, how many different types of gametes can he form?

4

A geneticist examines a somatic cell from a fly during metaphase of mitosis and determines that 16 chromatids are present. If a germ-line cell from this species divides by meiosis, then at the end of meiosis I (including the first cytokinesis) each cell will contain

4 chromosomes with 8 DNA molecules.

In a two-point cross to map genes A and B, you obtained 98 recombinant types and 902 parental types among the offspring. How far apart are these genes?

9.8 cM

What is the relationship between recombination frequency and the actual physical distance on a chromosome?

As physical distance increases, the recombination frequency first increases in a linear fashion, but gradually levels off to a frequency of 0.5. OR As physical distance increases, the recombination frequency first increases, but then decreases.

Which statement about calico cats is false?

Calico cats can be male or female.

Which of the following statements about crossing over is false?

Crossing over takes place between sister chromatids.

______ cells contain one set of chromosomes.

Haploid

Height is a trait that shows continuous variation in humans. In pea plants, on the other hand, the tall allele is dominant over the short allele and there are no intermediate heights. What is the best explanation for this difference?

Height is a polygenic trait in humans.

In humans, the male has an X and a Y sex chromosome. The human female has two X chromosomes. In birds, the female has a Z and a W sex chromosome while the male has two Z chromosomes. Which of the following statements is accurate about which parent determines the gender of the offspring based on inheritace of the necessary sex chromosome?

In humans, the male determines the gender of the offspring, and in birds the female determines the gender.

During anaphase I, which best represents segregation of the chromatids that make up one pair of homologues? (M represents a maternal chromatid and P represents a paternal chromatid. Assume no crossing over occurs.)

M and M to one pole; P and P to the other pole.

______ is a process of nuclear division which reduces the number of chromosomes per cell from 2 sets to 1 set.

Meiosis

Why isn't mitochondrial DNA a unique identifier?

Mitochondrial DNA is inherited through the maternal lineage. All offspring inherit their mother's mitochondria, and therefore the same mitochondrial DNA. As a result, all family members that share a maternal lineage would have the same mitochondrial DNA. Mitochondrial DNA can therefore be used to confirm or eliminate a person's relationship within a maternal line, but cannot be used to identify a specific individual.

The geneticist who discovered the white eye mutation in Drosophila and helped establish that genes are carried on chromosomes was

Morgan.

A person who has lost a large amount of blood but is still alive is found in a wrecked automobile under a highway bridge. Several people are helping the paramedics load the victim into the ambulance. After the ambulance has departed for the hospital, you overhear the following conversation from the persons who helped the paramedics. "I am certain that when that guy gets to the hospital, they will transfuse him with any blood that they have in the blood bank since he has lost so much blood." The other person says, "Yeah, I bet you're right!" Having had a biology course, you know which blood could be safely given to anyone. Select it below.

O

You are a forensic technician working on a DNA sample obtained from a crime scene. Your job is to compare the unknown DNA sample with known DNA samples collected from five different suspects. Preliminary analysis using only a few DNA markers revealed that the unknown sample could possibly match two of the suspects. After consulting the case file, you find out that these two suspects are brothers (but not twins). You realize that you will have to do a more detailed analysis on the samples so that you can distinguish between the brothers and determine which brothers' DNA matches the unknown sample. Why can't you use mitochondrial DNA to distinguish between these two suspects?

The brothers share the same mitochondrial DNA.

The synaptonemal complex is

a network of proteins that holds homologues together.

When Mendel crossed purple-flowered pea plants with white-flowered pea plants, he never got offspring with flowers that had an intermediate color. This was counter to the theory of

blending inheritance.

Let Cy = curly wings and Cy+ = wild type. In Drosophila, the Cy allele behaves as a dominant mutation that produces curly wings in the heterozygous condition (Cy/Cy+), but also behaves as a recessive lethal mutation. Flies homozygous for the Cy allele die before reaching adulthood. If you crossed flies heterozygous for the Cy allele, what phenotypes would you find in the adult F1 generation?

both wild type and curly wings

Genetic exchange between 2 homologous chromosomes is called

crossing over.

In humans, if an XY individual had a deletion of the SYR gene, that person would

develop as a female.

A secretor (allele seS) is a person who secretes their blood type antigens into body fluids such as saliva. By comparison, a non-secretor (allele seNS) does not. A person's status as a secretor or non-secretor is independent of blood type. Consider the following inheritance pattern of this trait: The most-likely explanation for this inheritance pattern is that the secretor trait is

dominant.

As a genetic counselor, you are constructing a human pedigree for a particular disease. You note that every generation shows the trait, suggesting that the trait is

dominant.

An extensive study was conducted on identical twins who were separated at birth. Among other things, the study showed that the individual from each pair who received better nutrition during childhood tended to score higher on standardized intelligence tests. This can best be described as an example of how

environment alters phenotype.

Sometimes, one gene pair will interfere with the expression of a second gene pair in an interaction called

epistasis.

The allelic make up of a cell or individual is referred to as its

genotype.

In animals, the cells that will eventually undergo meiosis to produce gametes are set aside early in development. These are called

germ-line cells.

Which of the following animals is a genetic male?

grasshopper XO

Sometimes, when Mendel crossed two pea plants with each other, he obtained a phenotypic ratio of 3:1 purple-flowered pea plants to white-flowered pea plants. These results are consistent with which set of parents?

heterozygous purple pea plant and heterozygous purple pea plant

A diploid individual carrying two different alleles at a given gene locus is called

heterozygous.

If fertilization involves two gametes that contain different alleles of a given gene, the resulting offspring is

heterozygous.

A diploid organism that has two identical alleles for a given trait is called _______ for that trait.

homozygous

A diploid individual carrying two identical alleles at a given gene locus is called

homozygous.

A genetic _____ indicates the distances between gene loci measured in terms of the frequency of recombination.

map

Which of the following produces new cells that are genetically identical to the original cell?

mitosis

All of the following increase genetic variation EXCEPT

mitosis.

The Rec8 protein holds sister chromatids together during meiosis. If an individual has a mutation that prevents degradation of Rec8, this would most likely prevent

normal segregation during meiosis II.

Sickle cell anemia is caused by a defect in the

oxygen-carrying pigment hemoglobin.

The observable expression of the genes present in an organism is called its

phenotype.

If an individual allele has more than one effect on the phenotype, this is called

pleiotropy.

Any genetic differences between individuals in a population are called

polymorphisms.

A Punnett square is generally used to

predict the genotypic ratio among the offspring.

Crossing over between homologous chromosomes takes place during

prophase I.

You are a forensic technician working on a DNA sample obtained from a crime scene. Your job is to compare the unknown DNA sample with known DNA samples collected from five different suspects. Preliminary analysis using only a few DNA markers revealed that the unknown sample could possibly match two of the suspects. After consulting the case file, you find out that these two suspects are brothers (but not twins). You realize that you will have to do a more detailed analysis on the samples so that you can distinguish between the brothers and determine which brothers' DNA matches the unknown sample. Which of the following will help you distinguish between the two final suspects?

single nucleotide polymorphisms (SNPs)

The pairing of chromosomes along their lengths, which is essential for crossing over, is referred to as

synapsis.

The pairing of homologous chromosomes is called

synapsis.

A life cycle that regularly alternates between haploid and diploid stages is found in all of the following EXCEPT

the bacterium E. coli

In Drosophila, the sex of an individual is determined by

the number of X chromosomes.

You are comparing the events of meiosis I in cells from several different organisms. You come across one species in which you do not observe any chiasmata. The best conclusion to make is

there is no crossing over between non-sister chromatids

Diploid organisms use meiosis to produce haploid cells. Meiosis consists of how many rounds of nuclear division?

two

The cell produced by the fusion of an egg and a sperm is the

zygote.