BI100 Practice Quizzes (Ch. 10-13)

A woman with a BRCA1 mutation ______.

...is at increased risk of developing breast cancer.

What are the chances that a curly-haired father and a straight-haired mother can give birth to a child with curly hair?

0%

A phenotypically normal woman marries a man with Huntington disease, an autosomal dominant disorder. What were the LARGEST chances their child would get the disease? (Draw a Punnett Square to help you determine the answer.)

100% chance.

A diploid cell of baker's yeast has 32 chromosomes. How many pairs of homologous chromosomes are present in a diploid cell of baker's yeast? How many chromosomes are present in each of its haploid gametes?

16 homologous pairs; 16 chromosomes in each gamete.

Two healthy individuals have a child who has cystic fibrosis, an autosomal recessive disease. What were the chances of this happening? (Draw a Punnett square to help you determine the answer.)

25% chance

A potential cancer-causing gene coding for a protein with cell cycle control responsibilities is a _____, and a gene coding for a protein that stimulated cell division is a ______.

carcinogen; proto-oncogene

A gamete is aneuploid if _____. a. There are more than 23 chromosomes in the cell. b. One or more sister chromatids fail to separate in meiosis II. c. There are fewer than 23 chromosomes in the cell. d. All of these. e. One or more homologous chromosomes fail to separate in meiosis I.

d. All of these.

The mutant BRCA2 gene predisposes people to cancer. If mutant BRCA2 runs in Isadora's family, will she automatically get cancer?

e. B and D Although inherited genes may carry an increased predisposition towards cancer, it is often nonhereditary mutations that lead to cancer. More than one mutation is needed to develop cancer.

All of these statements are true regarding S. aureus EXCEPT: a. it can be transmitted from person to person through used bar soap. b. it can secrete toxic substances that can interfere with cellular functions. c. it can cause pimples, boils, and wound infections in otherwise healthy individuals. d. all of these e. nearly 1% of the U.S. population is colonized with S. aureus.

e. Nearly 1% of the U.S. Population is colonized with S. aureus.

DNA mutations can arise from uncorrected errors in DNA replication, inheritance, and ______. a. a poor diet lacking in vitamins and minerals b. abnormal cell division c. chronic sleep deprivation d. catching an influenza virus from a person with mutated genes e. environmental insults

e. environmental insults

In diploid organisms, having two homologues of each chromosome can be beneficial if one allele of a gene encodes a nonfunctional protein. Can haploid organisms survive having nonfunctional alleles? Explain your answer.

If a haploid organism (with only one allele of each gene) has a nonfunction allele as its only copy of an essential gene, it will not be able to survive.

Which statement about decreasing a woman's breast cancer risk if she inherits one of the mutant BRCA genes is true? a. Woman cannot decrease her cancer risk, so she might as well live life to its fullest b. None of these. c. Diet and lifestyle changes will effectively decrease her risk to near zero. d. Surgical removal of the breasts will decrease a woman's cancer risk to near zer. e. She can take several medications that make it almost impossible to get breast cancer, even if she inherits the BRCA gene

None of these.

A woman with a BRCA1 mutation

is at increased risk of developing breast cancer.

A chemical that causes alterations in DNA is a ______, and if this chemical causes cancer it is called a(n) _______.

mutagen; carcinogen.

If a man has an X-linked recessive disease, can his sons inherit that disease from him?

No, all his sons inherit their X chromosomes maternally.

Which woman would be most likely to benefit from genetic testing for breast cancer?

A 25-year-old woman whose mother, aunt, and grandmother had breast cancer.

Which combination contains the normal chromosome number?

A Human egg - 23; a human sperm - 23; a human zygote - 46

In an otherwise normal cell, what happens if one mistake is made during DNA replication?

A cell cycle checkpoint detects the error and pauses the cell cycle so the error can be corrected.

Which people could have a boy with Duchenne Muscular dystrophy (DMD)?

A male without DMD and a carrier female.

Are all mutations bad?

No, some mutations may have no effect on the encoded protein (silent mutations). Other mutations may be beneficial.

We would all have many more mutations in our genes if not for the _____.

Activity of repair enzyes

Which of the following is a known mutagen? a. Sunlight b. Cigarette smoke c. Charred meat cooked at high temps d. X-rays

All of the answers are known mutagens.

Why is age a risk factor for cancer?

All of the following: Age provides more time for the cancer cells to accumulate Age extends the amount of exposures to environmental factors, which can lead to the progression of cancer. Age causes additional mutations to be acquired that can predispose one to cancer.

What would you say to a niece if she asked you how she could reduce her risk of breast cancer?

All of the following: Utilize early screening Reduce sun exposure Reduce alcohol consumption Avoid tobacco

If two women have identical alleles of the suspected 20 height-associated genes, why might one of those women be 5'5 and the other 5'8"?

Because environmental factors also play a role in the phenotype of this trait.

Which of these can results in a trisomy such as Down syndrome?

An egg with 24 chromosomes fertilized by a sperm with 23 chromosomes.

Which of these is likely results of nondisjunction in human meiosis?

Aneuploid eggs or sperm.

From which parent did Emily inherit cystic fibrosis? Explain.

As cystic fibrosis has an autosomal recessive inheritance pattern, Emily must have two recessive alleles and therefore inherited one recessive allele from each parent.

In an otherwise normal cell, what happens if ne mistake is made during DNA replication? A. Mistakes are never made during DNA replication. B. A Cell cycle checkpoint detects the error and pauses the cell cycle so error can be corrected. C. Nothing; mistakes just happen. D. The cell will begin to divide out of control, forming a malignant tumor. E. The mutation will be inherited by the individual's offspring.

B. A cell cycle checkpoint detects the error and pauses the cell cycle so the error can be corrected.

People like Lorene Ahern have inherited a mutated version of BRCA1. Why does this mutation pose a problem? Why are these people at high risk of developing breast cancer when they still have a functional BRCA1 allele? Describe how the protein encoded by normal BRCA1 compares to that encoded by mutant alleles of BRCA1.

BRCA1 encodes a protein that plays an important role in DNA repair: it is a tumor suppressor gene. A BRCA1 mutation in one allele means that cells are relying n the other (function) allele of BRCA1. If a subsequent single mutation disrupts that other allele f BRCA1, that single mutation is sufficient to eliminate all BRCA1 function in the cell. This is because mutant alleles of BRCA1 encode proteins that cannot function in DNA repair.

What is the role of BRCA1 in normal cells?

BRCA1 is a tumor suppressor gene that encodes a protein involved a DNA repair of mutation.

What is the role of BRCA1 in normal cells?

BRCA1 is a tumor suppressor.

How does an acquired mutation in a gene alter the function of a cell?

Base pair mutations in a gene are passed directly into mRNA via transcription.

There are several points during the cell cycle when the cell with check to be sure everything's progressing normally, without mistakes, and confirm that the cell should continue the next phase of the cycle. When do these "cell cycle checkpoints" occur?

Between G1 and S, between S and G2, and during mitosis.

Which of the following can cause cancer to develop and progress?

Both an oncogene and a mutated tumor suppressor gene

Why do people with "inherited cancer" often develop cancer at a relatively young age?

Cancer cannot be truly inherited, but certain alleles weaken the normal control points that prevent cancer, and this causes cancer to appear earlier in life.

A specific gene, called GRAB, prevents a cell from entering mitosis if there are any signs of DNA damage. This means GRAB would be a type of...

Cell Cycle Checkpoint.

Why do some people have unusual chromosome combinations, such as XYY and XXX?

Errors occurred in chromosome segregation during meiosis in their fathers or mothers.

Predict the sex of a baby with an X sex chromosome.

Female.

Predict the sex of a baby with an XX pair of sex chromosomes.

Female.

What would you say to a niece if she asked you how to she could reduce her risk of breast cancer? (Assume there is no family history of breast cancer.) How might each of your suggestions reduce her risk?

Given that there's no family history of breast cancer, it is unlikely that your niece has a mutation in BRCA1. Therefore, her risk-reduction strategies won't need to include early breast cancer screening, but they should include avoiding known carcinogens (e.g., tobacco), maintaining a healthy weight, limiting alcohol consumption, and making informed decisions about hormonal treatments (e.g., birth control or postmenopausal hormone therapy) and, if possible, the timing of pregnancies. Carcinogens such a tobacco increase cancer risk by causing mutations that may disrupt normal cell cycle progression. Obesity is a risk factor for many cancers, and postmenopausal obesty is a particular risk for breast cancer. Alcohol is also a risk factor for breast cancer. Some hormonal interventions can increase breast cancer risk (e.., oral contraceptives increase risk, but this risk seems to be negated 10 years after stopping the use of oral contraceptives). For women who choose to have children, having the first child earlier in life, and having having more children, reduces the risk of breast cancer.

A 28-year-old male graduate student was born with an inherited predisposition to colon cancer due to a mutation in a DNA repair gene called MLH1. He has recently been diagnosed with colon cancer. At the cellular and genetic level, was he born with colon cancer?

He was not born with colon cancer, but with a genetic predisposition to colon cancer. At birth, his colon cells were identical to his liver cells; they all had one normal copy of MLH1 and one mutated copy of MLH1. It would thus require a single mutation in the non-mutated MLH1 allele in a colon cell to allow that cell to allow that cell to progress to colon cancer. Now that he has colon cancer, both copies of the MLH1 gene in his cancer cells have the mutation, while his normal colon cells still have one normal copy and one mutated copy of MLH1.

How is codominant inheritance different from incomplete dominant inheritance?

In codominance, two alleles are expressed equally; in incomplete dominance, heterozygotes have an intermediate phenotype.

Which form of breast cancer treatment is least specific for the cancer cells?

Lumpectomy

What are some of the similarities between tumor suppressor gene and oncogenes?

In their nonmutant states, both tumor suppressor genes and (proto-)oncogenes are important for proper cell cycle progression. In their mutant states, both contribute to the development and progression of cancer. Normal tumor suppressor genes act to prevent the cell cycle from the progressing inappropriately (e.g., when there is rampant DNA damage). When mutated, tumor suppressor genes can no longer pause the cell cycle when necessary, and cells with DNA damage may continue to divide. Normal proto-oncogenes act to promote cell division in response to appropriate signals to divide. When proto-oncogenes are mutated to oncogenes, they continuously "push" cells to divide, even in the absence of growth-promoting signals.

Which is the correct order of events in which breast cancer might develop?

Inheritance of a mutant BRCA gene > Replication errors create an oncogene > Mutation of p53 > additional mutations permit spreading

Predict the sex of a baby with an XXY combination of sex chromosomes.

Male.

Why are more males than females affected by X-linked recessive genetic diseases?

Males have a Y chromosome that cannot mask the X-linked recessive allele.

Which statement is true about Y chromosome analysis?

Is it commonly used to determine paternity and ancestry.

Which statement accurately describes cancer development?

It is a multistep process by which multiple mutations cause a series of events that lead to cancer.

What would happen if the enzyme that makes DNA added a nucleotide to the middle of a coding region of a gene?

It would change the reading frame of the DNA and possibly lead to a change in the amino acid sequence of the protein made from that gene.

Which family history suggests a risk of inherited breast cancer due to BRCA1 mutations?

Many female relatives diagnosed with breast cancer at an early age.

A mutation causes a substitution of one amino acid for another in the encoded protein. What type of mutation is this?

Missense.

Meiosis differs from mitosis in all the following ways, EXCEPT

Mitosis results in 4 cells whereas meiosis results in 2.

Which inheritance pattern includes an environmental contribution?

Multifactorial.

Why is type O- the "universal donor"?

No surface markers are present on the O- blood cells to react with the recipient's immune system.

Human skin color ranges from very light to dark black, with many distinct skin tones in between. What type of inheritance pattern governs skin color?

Polygenic inheritance.

How are polygenic and multifactorial traits different?

Polygenic traits are genetically based. Multifactorial traits have both genetic and environmental influences.

How is genetic diversity created in meiosis?

Recombination of homologous chromosomes occurs in meiosis I.

Why does wearing sunscreen reduce cancer risk?

Sunscreen can reduce the chance of mutations caused by exposure to UV radiation present in sunlight.

Which of these most influences the development of a female fetus?

The absence of a Y chromosome.

What is different about red blood cells from a person with type AB blood, compared to those from other blood types?

They carry A and B type surface markers, so they are universal acceptors of blood.

How do the two alleles of the CFTR gene in a lung cell differ?

They were inherited from different parents.

Which of these can be determined by amniocentesis and karyotyping?

Trisomy 21.

Look at the mutagens in Infographic 10.3. Of these, which are most easily avoidable, and which are not avoidable?

UV radiation, smoking, and charred meat are avoidable. X-rays may be medically necessary in certain circumstances. Depending on where you live, pollution and pesticides may not be entirely avoidable. Exposure to certain infectious agents can be minimized by taking precautions. Exposure to mutagenic free radicals generated by cellular processes cannot be avoided.

Consider your brother and your son. If you are male, which statement is correct?

You and your brother inherited the same Y chromosome from your dad, and you passed the same Y chromosome on to your son.

Which of these does not cause cancer to develop and progress?

a proto-oncogene and a tumor suppressor gene acting together.

If you wanted to change your lifestyle to reduce your risk of developing cancer, what specific steps could you take with respect to each of the following? Be as specific as you can. Take your age and gender into consideration as you consider each factor.

a. Alcohol consumption is a risk factor for many cancers, including oral and breast cancer. Reducing alcohol consumption can reduce the risk of cancer, particularly of breast and oral cancer. b. Sun exposure is a risk factor for many kinds of skin cancer, including melanoma. Avoiding sun exposure, especially between 10:00 a.m. and 2:00 p.m., and wearing protective clothing and sunscreen can help limit exposure to mutagenic radiation in sunlight. c. Tobacco use is a risk factor for many cancers, including lung, oral, bladder, and kidney cancer. Both cigarette tobacco and smokeless (chewing) tobacco are risk factors. Chemical compounds in tobacco products can damage DNA and lead to mutations. People should avoid smoking and all forms of tobacco use, and seek help for quitting. d. Many pesticides are carcinogenic. The average consumer can reduce exposure to pesticides by washing fruits and vegetable. It is important that agricultural workers follow label instructions in applying pesticides and wear protective equipment when working with any carcinogenic chemicals. e. Cooking meat at high temperatures (e.g., on a very hot barbecue grill) can result in the formation of carcinogens caused by chemical reactions that occur in the meat at high temperatures. Eating meat that has been cooked for longer times at lower temperatures reduces exposure to these carcinogens.

A mutation can cause a change _____. a. all of these b. in the amino acid sequence of a protein c. that is beneficial to the cell d. in the shape of protein e. the way the cell cycle is regulated

a. all of these (in the amino acid sequence of a protein; that is beneficial to the cell; in the shape of a protein; the way the cell cycle is regulated)

All of the following are true of recessive alleles, EXCEPT...

a. they are never transcribed and therefore never produce protein.

A newly identified mutation in mice, called "darkened dorsal," causes a dark stripe along the mouse's back. This mutation is located at a specific location on chromosome 2. A different sequence at this same chromosomal position results in a fur color pattern called "nonagouti." Based on this information, darkened dorsal and nonagouti are different...

alleles for the same gene.

Why does wearing sunscreen reduce cancer risk? a. Sunscreen can activate checkpoints in skin cells. b. Sunscreen can reduce the chance of mutations caused by exposure to UV radiation present in sunlight. c. Sunscreen can repair damaged DNA. d. Sunscreen can prevent cells with mutations from being destroyed. e. It does not reduce cancer risk; sunscreen causes mutation and actually increases cancer risk

b. Sunscreen can reduce the chance of mutations caused by exposure to UV radiation present in sunlight.

At which point does a mutation exert its potentially dysfunctional effects in a cell? a. during DNA replication b. after a protein is produced c. during protein translation d. during DNA transcription e. only during cell division

b. after a protein is produced

If an individual has a germ cell mutation, which of these is a possible source of that mutation? a. a maternal allele only b. a maternal or paternal allele c. overuse of alcohol d. a paternal allele only e. excessive sun exposure

b. maternal or paternal allele

Tumors that will not spread through the body are _____, and those that do spread are termed _______.

benign; malignant.