CHAPTER 13

In humans, redgreen colorblindness is caused by a recessive allele on the X chromosome.... In this case, what is the probability that there first child would be a girl with hemophilia?

...

At an autosomal gene locus in humans, the allele for brown eyes is dominant over the allele for blue eyes. At another gene locus, located on the X chromosome, a recessive allele produces colorblindness while the dominant allele produces normal color vision. A heterozygous browneyed woman who is a carrier of colorblindness marries a blueeyed man who is not colorblind. The woman becomes pregnant and an ultrasound test shows that the child is a girl. What is the probability that she will be colorblind? (Enter the probability as a percent. Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5)

0

How many Barr bodies does a normal human female contain in each diploid cell?

1

What would be the results of a test cross with the F1 flies?

1 brown, thin: 1 red, heavy

Given that these 2 gene loci are very closely linked, the phenotypic ratio in the F2 generation should be closest to

1 brown, thin: 2 red, thin: 1 red, heavy

In a twopoint 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

In the fruit fly Drosophila, there is a dominant gene for normal wings and its recessive allele for vestigial wings. Normal wings and red eyes 420 Vestigial wings and red eyes 80 Normal wings and purple eyes 70 Vestigial wings and purple eyes 430 According to these data, what is the distance, in centimorgans, between these 2 gene loci? (Enter the number only without the units. For example, 100 cM would be entered as 100)

15

Given that these 2 gene loci are very closely linked, the genotypic ratio in the F2 generation should be closest to

1:2:1

In humans, individuals with trisomy of the ______ chromosome are most likely to survive until adulthood.

21st

At an autosomal gene locus in humans, the allele for brown eyes is dominant over the allele for blue eyes. At another gene locus, located on the X chromosome, a recessive allele produces colorblindness while the dominant allele produces normal color vision. A heterozygous browneyed woman who is a carrier of colorblindness marries a blueeyed man who is not colorblind. What is the probability that their first child will be a blueeyed female who has normal color vision? (Enter the probability as a percent. Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5)

25

In fruit flies () there is a dominant allele for red eyes and a recessive allele for white eyes. These alleles are located on the X chromosome. If a heterozygous redeyed female is mated with a whiteeyed male, what percentage of the offspring are expected to be whiteeyed females? ( Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5 )

25

In humans, hemophilia is caused by a recessive allele on the X chromosome. Suppose a man with hemophilia marries a normal woman whose mother had hemophilia. If an ultrasound test shows that their first child is a girl, what is the probability that she has hemophilia? (Enter the probability as a percent. Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5 )

50

In humans, hemophilia is caused by a recessive allele on the X chromosome. Suppose a man with hemophilia marries a normal woman whose mother had hemophilia. What is the probability that their second child will have hemophilia? ( Enter the probability as a percent. Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5 )

50

How did the development of anonymous markers aid in the production of a human genetic map?

Anonymous markers are genetic markers that do not cause a detectable phenotype, but can be detected by molecular techniques. The markers correspond to specific and unique chromosomal regions, thereby allowing for the identification and ordering of particular segments of DNA. Such information was essential to the generation of a human genetic map.

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.

Which statement about calico cats is false?

Calico cats can be male or female.

In some species, sex determination is influenced by environmental temperature during development. If you wanted to determine the temperature at which one would obtain a 1:1 sex ratio in a particular species of turtle, which of the following experiments would best address this question?

Grow the turtles in five different incubators at temperatures of 22oC, 24oC, 26oC, 28oC, and 30oC.

In some human populations, the proportion of individuals who are heterozygous for the sickle cell allele is much higher than would be expected by chance alone. Why?

Heterozygous individuals have an advantage over individuals with two normal alleles.

_______________ is a human hereditary disease that is caused by a dominant allele but does not show up in affected individuals until they are in middle age.

Huntington's disease

Huntington's disease is caused by a single dominant allele. It is a lethal disease, yet it persists in the human population. Which of the following statements best describes why?

Huntington's disease presents symptoms in midlife, after most people have already had offspring.

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?

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

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

Morgan

Suppose you are carrying out a series of crosses with an insect where the mechanism of sex determination is unknown. You discover a mutant female with short bristles and decide to cross it with a wild type male that has normal bristles. Half of the F1 progeny have short bristles but all of these shortbristled F1 progeny are males. Based on these results, a valid hypothesis would be

Males are ZZ, females are ZW, and short bristles are caused by a dominant allele on the Z chromosome

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

Map

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.

Traits that are controlled by genes located on the X chromosome are said to be ________________.

Sex-linked

The theory of chromosomal inheritance was first proposed by

Sutton

Why can't you use mitochondrial DNA to distinguish between these two suspects?

The brothers share the same mitochondrial DNA.

In Drosophila, the sex of an individual is determined by

The number of X chromosomes

Allele pairs are most likely to assort independently of one another when

They are on different chromosomes

A human female with only one X chromosome is said to have a condition called

Turner syndrome.

In 1910, Morgan did a series of experiments with the fruit fly Drosophila, an organism where females are XX and males are XY.... Suppose Morgan has found that half of the F1 progeny had white eyes but all of these whiteeyed F1 were females. In this case, a valid hypothesis would be flies

White eyes is caused by a dominant Xlinked allele

If an XY human had a genetic disorder that causes insensitivity to androgens, that person's genotype and phenotype would be

XY, female.

In sickle cell anemia, the defective hemoglobin differs from the normal hemoglobin by

a single amino acid substitution.

If you needed to determine the order of genes on a chromosome, you should perform

a threepoint cross.

Of the 23 pairs of human chromosomes, 22 pairs are homologous and are found in both males and females. These are called ________.

autosomes

In humans, if nondisjunction led to an individual with a genotype of XO, that person would

be female because each cell lacks a Y chromosome.

In humans, if nondisjunction led to an individual with a genotype of XXY, that person would

be male because each cell has one Y chromosome.

Which offspring inherit all their mitochondrial DNA from their mother and none from their father?

both sons and daughters

A 39yearold woman is in her sixth week of pregnancy. Due to her advanced age, she is at higher risk for having a baby with Down's syndrome than younger pregnant women. She would like to find out as early as possible whether or not her baby has Down's syndrome. Her doctor should suggest

chorionic villi sampling.

Genetic exchange between 2 homologous chromosomes is called

crossing over

The number of allele pairs that assort independently in an organism is generally much higher than the number of chromosome pairs. This phenomenon is due to

crossing over

The most common fatal genetic disorder of Caucasians is

cystic fibrosis.

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

develop as a female.

In Drosophila, dosage compensation is controlled by the malespecific lethal (MSL) complex consisting of MSL proteins and roX RNAs. Based on what you know about dosage compensation, the role of the MSL complex in males would be to

double the level of expression of genes on the X chromosome.

Nondisjunction of a single pair of autosomes can lead to all of the following except

euploidy

Amniocentesis is a procedure that is normally used

for diagnosis of genetic disorders.

Which of the following animals is a genetic male?

grasshopper XO

A test cross can be used to do all of the following except

identify the chromosome on which a gene is located.

In Morgan's experiments, the white eye allele in Drosophila was shown to be

located on the X chromosome

Humans who have lost one copy of an autosome are called

monosomic

Occasionally, chromosomes fail to separate during meiosis, leading to daughter cells that have an abnormal number of chromosomes. This phenomenon is called

nondisjunction

Sickle cell anemia is caused by a defect in the

oxygen carrying pigment hemoglobin.

Any genetic differences between individuals in a population are called

polymorphisms.

The classic experiments performed by Creighton and McClintock in Maize

provided evidence for the physical exchange of genetic material between homologues.

Hemophilia is caused by a

recessive allele on the X chromosome.

If a human female has 2 Barr bodies per cell, it is almost certain that

she developed from a fertilized egg with 3 X chromosomes

You are a forensic technician working on a DNA sample obtained from a crime scene... Which of the following will help you distinguish between the two final suspects?

single nucleotide polymorphisms (SNPs)

A deletion of a particular stretch of chromosome 15 can cause either PraderWilli syndrome or Angelman syndrome, depending on

the parental origin of the normal and deleted chromosome.

Morgan's student Sturtevant demonstrated that the recombination frequencies between a series of linked genes is additive. Examine the following recombination data from Sturtevant, and determine the proper order of the genes on the Drosophila X chromosome. Assume y is in the 0.0 position.

y w v m