Biology BSC1005 SSC Ch.6-8

polygenic

Eye color is a function of the genes responsible for melanin production and the genes controlling the structure of the iris.

Statement: This figure depicts asexual reproduction in the form of mitosis.

False: Eukaryotic cells can undergo asexual reproduction through mitosis, but this image shows cell division of a bacterium via binary fission.

Most traits in humans display Mendelian inheritance.

False: Most traits in humans are complex and influenced by many genes.

How do the chromosomes in a male human differ from those in a female human?

Males have a Y chromosome, which females lack.

If both a father and a mother have a good sense of humor, they should expect a maximum of 25% chance that they would have an offspring without a good sense of humor.

False, Sophisticated traits in humans, such as a sense of humor, are not controlled by single genes. Instead, they are controlled by many interactions of many genes as well as the environment.

separates homologous chromosomes

Meiosis I

What information in a pedigree would indicate that a condition is likely sex-linked?

Most of the affected individuals are males.

Even in simple Mendelian genetics, an offspring's traits can be hard to predict. For example, two parents that do not exhibit the sickle-cell anemia trait can produce an offspring with sickle-cell anemia. This indicates that the sickle-cell trait must be what kind of trait?

Recessive

Put the potential offspring genotypes in order from highest expected frequency to lowest expected frequency for a cross in which both parents have the RrTt genotype.

RrTt rrTt RRtt

In humans, cells containing two copies of each of the 23 chromosomes are called -. One copy is from the mother, and one is from the father. These two copies are - to each other. After the S phase and DNA replication, each chromosome consists of two sister chromatids. These two chromatids are - to each other and are linked at the -, so the chromosomes are shaped like an X.

1. diploid 2. homologous 3. identical 4. centromere

A woman carries two alleles for an autosomal dominant genetic condition. Her husband does not possess the allele. What are the chances that their offspring would inherit the condition?

100%

The following pedigree shows the inheritance of an autosomal recessive condition. What are the chances that the female in generation II is a carrier for this condition?

100%

In cattle, the allele that causes horns to grow is recessive. Another recessive allele causes the cows to grow abnormally large and muscular. These muscular cows are often called Belgian blue cows. If a cow that is heterozygous for both the horn and Belgian blue trait genes passes on the allele for growing horns to an offspring, what are the odds that the parent cow also passes on the allele for becoming very muscular to that offspring?

50%

Haploid

(genetics) an organism or cell having only one complete set of chromosomes ex. Gametes

Diploid

(genetics) an organism or cell having two sets of chromosomes or twice the haploid number ex. Skin cell and zygote

A man possesses an allele for a recessive X-linked genetic condition, and his wife does not possess the allele. What are the odds that the couple's son will express the condition?

0%

In pea plants, the tall allele (T) is dominant to the short allele (t) and the yellow pea allele (Y) is dominant to the green pea allele (y). In a cross between a TTYy pea and a ttyy pea, what are the odds that the offspring will be tall and have green peas?

1/2

Consider a gene with two alleles that show complete dominance. When a homozygous recessive individual (qq) is crossed with a heterozygous individual (Qq), they have a 50 percent chance of producing a homozygous recessive offspring. The next time these two individuals breed, what are the chances that they will once again have a homozygous recessive progeny?

50%

M has Huntington disease, a progressive brain disorder caused by a mutation in the HTT gene located on chromosome 4. This allele is dominant and M is heterozygous for the allele. M and his wife S, who does not have the Huntington allele, have had one child. What is the chance that their child will be diagnosed with Huntington disease?

50%

Why is it difficult to study the inheritance of genetic disorders in humans?

A. Humans usually have just a few offspring in their lifetime. B. Ethical issues prevent researchers from doing many kinds of experiments on humans. C. Humans pick their own mates with whom to have children.

In Labrador dogs, coat color is controlled by the genotypes of two genes. In one gene, the dominant allele, B, produces black fur, and the recessive allele, b, produces brown fur. However, if a second gene possesses two recessive alleles, ee, the dog produces yellow fur, regardless of the genotype of the first gene. If two dogs that are heterozygous for both genes, BbEe mated, what would be the frequency of the three phenotypes, black, brown, and yellow?

Black: 9/16 Brown: 3/16 yellow: 4/16

Uncontrolled cell division can lead to one of the most deadly diseases in the United States. Which disease is it?

Cancer

- contain multiple - which have different versions called -

Chromosomes genes alleles

A great deal of the risk of many human diseases, such as coronary heart disease and type 2 diabetes, is dependent upon lifestyle choices. Which word correctly describes what this indicates about the patterns of inheritance of these diseases?

Complex

In certain types of cells, like liver and heart tissues, tetraploid cells are normal and common. However, sometimes the formation of tetraploid cells may be an unintentional result of exposure to chemicals or other factors. These rogue tetraploid cells may eventually lead to tumor formation. These cells most likely form due to a failure at which phase of the cell cycle?

Cytokinesis

In which of the following scenarios is the offspring most likely to express the genetic condition?

Only the mother is a carrier for an X-linked recessive condition. The offspring is a male.

cell division

Process by which a cell divides into two new daughter cells ex. mitosis

In which two phases of meiosis does crossing-over occur?

Prophase I and Metaphase I

How do most autosomal recessive alleles that lead to lethal diseases persist in human populations?

The disease-causing allele can "hide" in the heterozygous condition.

What would you expect for an individual with the genotype XXY?

The individual would develop as a male.

Why did Dr. Wiskott suspect his young male patients had a genetic disease rather than one caused by an infectious, environmental, or toxic agent?

The other children in the family were healthy.

In one experiment, Mendel crossed pea plants with purple flowers and pea plants with white flowers. The offspring of this cross all had purple flowers. Which statement best explains this pattern?

The purple flowered parent plants were homozygous dominant.

environmental

The sex of an alligator is determined by the temperature of the soil in which the eggs are buried.

The pedigree shown diagrams an X-linked gene. The individual indicated by the arrow is ___________ for the gene.

There is not enough information to determine the answer.

separates sister chromatids

meiosis 2 & mitosis

results in diploid cells

mitosis

The purpose of constructing a pedigree for a patient with a genetic disorder and their family is

to try to determine how the disorder may have been inherited.

Which of the following traits are Mendelian and which show more complex patterns of inheritance? Mendelian

yellow versus green pea color in pea plants

Which process contributes to genetic variation through the exchange of DNA between nonsister chromatids during prophase I of meiosis?

crossing-over

What type of molecule is found in the structures shown in blue in the center of this image?

deoxyribonucleic acid

Based on your knowledge of ploidy level in various human cells, would you expect human stem cells to be diploid or haploid?

diploid

A guinea pig has red eyes, which is the recessive condition. Its eye color alleles are bb. In this example, bb is its ___________ .

genotype

If a person has two different alleles for a given gene, the person is ________ for that gene.

heterozygous

In 4 o'clock flowers, flower color is controlled by a single gene with two alleles. The R allele produces red flower color, and the W allele produces white flower color. These alleles display incomplete dominance, and when both alleles are present, the flowers appear pink. Remember, when dealing with incomplete dominance, only capitals are used for the two traits because neither allele exerts dominance over the other. Match each of the following genotypes to the correct color of flowers. PF

heterozygous WR RW

If two alleles at a locus on homologous chromosomes are the same, the cell is ______; if the two alleles are different, the cell is _____.

homozygous; heterozygous

A diagram similar to a family tree that illustrates genetic relationships is called a -. These diagrams can be analyzed to investigate the inheritance patterns of genetic disorders. A genetic disorder that appears in an offspring of a family that has no history of the disorder is likely a - condition. Such an outcome suggests that - acted as a carrier for the disorder.

pedigree, recessive, both parents

Interphase

period of the cell cycle between cell divisions ex. G2 Phase, G1 Phase, & S Phase

Mendel's primary contribution to our understanding of genetic inheritance was

providing a mechanism that explains patterns of inheritance.

Chromosomes (not individual genes) are the paired structures that are shuffled, recombined, and then separated into gametes. Which explains the relationship of chromosomes to Mendel's laws?

the chromosome theory of inheritance

When Mendel crossed a set of "true breeding" purple flowered (PP) pea plants with a set of true breeding white flowered (pp) pea plants, he found that - of the offspring had purple flowers. This result on its own showed that the purple flower trait was - to the white flower trait, but to understand that the offspring carried one allele from each of the parents, he needed to -

1. all 2. dominant 3. cross the offspring with each other.

What could be a limitation of "personalized medicine" based on genetic testing?

Some diseases could involve so many genes that understanding all their relationships would be too difficult, making it challenging to develop practical, effective treatments. Not everyone may have access to genetic testing, so they wouldn't have access to "personalized medicine." Patients that have a genetic disposition toward a disease may not choose to remove the environmental triggers (i.e., smoking), which defeats the purpose of the testing.

Chromosomal replication produces two identical sister chromatids.

True: Sister chromatids result from DNA replication in the S phase and are identical to each other.

In a karyotype of a human female, which of the following would indicate a normal karyotype?

Two X chromosomes

Which best describes a gene?

a segment of DNA that codes for at least one trait

A trait's - is the combination of alleles that are present at the gene, and a trait's - is the outward expression of the trait. When there are two alleles for a gene, one dominant and one recessive, the - genotype shows the same phenotype as the homozygous dominant genotype.

1. genotype 2. phenotype 3.heterozygous

While studying the outcomes of reproduction in -, Gregor Mendel found that each individual carries - copy/copies of the allele for each trait and that - is/are passed on to each offspring. When studying inheritance of two different traits, Mendel found that the patterns of inheritance of one trait - on the patterns of inheritance of another trait. This concept is now called -

1. pea plants 2. two 3. one 4. has no effect 5. the law of independent assortment.

In modern terms, Mendel's law of - states that each gamete formed through - receives a -, while the law of - states that the alleles in those gametes are chosen -.

1. segregation 2. Meiosis 3. single allele of each gene 4. independent assortment 5. at random

Tess's sister is known to carry an allele for a single-gene recessive genetic disorder that is fatal in very early life. Tess's mother was tested for the allele and found not to carry it. What are the odds that Tess is a carrier for the allele?

1/2

What are the odds that two carriers for cystic fibrosis, an autosomal recessive disorder, would have an offspring with the cystic fibrosis disorder?

1/4

A recent study found that at least 180 different genes seem to be correlated with height in humans, which is partly why height is a continuous trait. If we imagine a much simpler scenario in which only 10 genes control height, and each of these genes displays simple Mendelian inheritance (i.e., there are only two alleles, tall and short, and tall is dominant to short) and shows equal contribution to height, how many different possible genetic height phenotypes would there be in humans?

11

The chemicals nonylphenol and BPA both disrupt cell cycles resulting in chromosomal abnormalities. Under normal conditions, each round of mitosis should result in two identical daughter cells. If you were to observe a cell containing 3 pairs of homologous chromosomes during a normal cell cycle, how many sister chromatids would you expect to find when mitosis begins?

12 sister chromatids

If the height of pea plants is controlled by a single gene, where the tall allele, T, is dominant to the short allele, t, how many different possible phenotypes of height would exist in total?

2

In humans, photic sneezing (sneezing when exposed to sunlight) and wet ear wax are both the result of dominant alleles, P and E, respectively. If a woman who is unaffected by photic sneezing but is heterozygous for wet ear wax marries a man who is heterozygous for photic sneezing but has dry ear wax, what percentage of their children would likely both sneeze when exposed to sunlight and have dry ear wax?

25%

The human ABO blood type trait displays four phenotypes: A, B, AB, and O. It is controlled by a single gene which has three possible alleles: A, B, and O. The A and B alleles are codominant, and the O allele is recessive to both A and B. How many different possible genotypes exist for this gene?

6

A woman's eggs carry an exact copy of one of the chromosomes from that woman's mother or father.

False: During meiosis, crossing-over allows mixing of the maternal and paternal chromosomes. Additionally, the chromosomes are divided and randomly assorted into gametes.

Two blue-eyed parents can produce a brown-eyed offspring. Blue eyes are recessive.

False: If two parents display the recessive trait, than they both must be homozygous recessive and neither would possess any dominant alleles to pass to their offspring.

The two cells resulting from meiosis are diploid, and they are further divided into four haploid cells.

False: In the S phase preceding meiosis, DNA has replicated, but the cell is still diploid because it has the same number of centromeres as the parent cell. The two cells resulting from meiosis I are haploid. Each haploid cell contains pairs of sister chromatids, so they must divide again to generate the four haploid gamete cells.

Mendel understood that genetic information was carried on material elements within the cell.

False: Mendel was correct in describing his laws, but he did not know the underlying mechanisms.

Skin and breast cancer cells that are undergoing uncontrolled cell division have been treated with chemicals that prevent them from proliferating by causing the cells to arrest before the DNA starts to replicate. These tumor cells have been arrested in which phase of the cell cycle?

G1 Phase

If a father is unaffected by an X-linked condition and the mother is a carrier, what is the probability of their children being affected?

Half of the sons will be affected.

This pedigree is, in fact, depicting members of a family that suffers from an autosomal recessive genetic disease, not WAS. What clues indicate that this is NOT the pedigree of an X-linked recessive disorder like WAS?

In the pedigree, an affected mother (I-2) has an unaffected son. This could not happen with an X-linked recessive disorder. In the pedigree, two unaffected parents (II-1 and II-2) have an affected daughter. This could not happen with an X-linked recessive disorder.

When geneticists first studied eye color, it was suggested that the "blue-eyed" trait was caused by a single recessive allele. Further study indicated that, while rare, blue-eyed parents could have a brown-eyed child. Which of the following statements best describes this trait and the reason for its occurrence?

It is a complex trait because the rules of dominance are not followed

Two cats are both heterozygous for hair length, Ll, and heterozygous for white hair, Ww. Short hair and white hair are dominant to long hair and colored hair, respectively. What are the odds that the pair's offspring would show the following phenotypes?

Lwh: 3/16 Lch: 1/16 Sch: 3/16 Swh: 9/16

pleiotropic

People carrying the gene for sickle cell anemia can also suffer from vision loss.

PKU is a genetic disorder which results in brain damage unless a special diet is followed. It is caused by a recessive allele found on chromosome 12. Alfredo and Lisa have a child with PKU. Alfredo has the disorder, but Lisa does not. What is Lisa's genotype for PKU? Use P to represent the normal allele and p to represent the PKU allele.

She must be Pp because she doesn't have PKU, but she did pass on a recessive allele to her child.

Researchers Ana Soto and Carlos Sonnenschein discovered breast cells multiplying in the absence of the required chemical estrogen because the plastic tubes that held the breast cells were contaminated by an endocrine disrupter. Similarly, another researcher, Dr. Patricia Hunt, discovered that female mice who drank from damaged plastic bottles ingested bisphenol A (BPA), which led to egg abnormalities. All of these troubling results were caused by disruptions of the normal cell cycle in those animals by chemical contamination from plastics. Which of the following statements are correct about the normal cell cycle?

Some cells enter G0 phase after cell division. The G1 and G2 phases allow the cell to check whether or not it is ready to divide. The S phase is required to replicate the chromosomes in the cell.

A man and his wife are both carriers for a recessive disease allele. If the couple has a child, which of the following statements is true?

The child has a 25 percent chance of being affected by the disease.

The disease discussed in the animation is caused by a recessive allele. Recessive alleles frequently do not produce a protein product. Dominant alleles, on the other hand, may produce a harmful protein. How might treating a dominant disorder with gene therapy differ from treating a recessive disorder with gene therapy, as discussed in the video?

The dominant disease allele needs to be inactivated so that it does not produce the harmful protein.

The round trait in peas is controlled by the R allele, and the r allele controls the wrinkled trait. If you were to perform a cross between one parent that was Rr and another that was rr, what is the chance that there would be wrinkled peas in the F1 generation?

There is a 2 out of 4, or 50%, chance.

The human genome has an estimated 25,000 genes on 23 chromosomes that can be affected by crossing-over and assorted into gametes. These gametes can then randomly combine into a diploid cell during fertilization. Given these numbers, about how many different combinations of chromosomes could be found in diploid offspring?

Trillions

In humans, the sex of an offspring is determined solely by the chromosomes donated by the male parent.

True: A male is the only sex that possesses the Y chromosome, which makes an offspring male. Therefore, it is solely the male parent's contribution of chromosomes that determines the offspring's sex.

Tongue rolling was thought to be an example of a human trait controlled by a single gene, but we now know that identical twins, who share 100 percent of their DNA sequences, will only share the tongue-rolling trait 70 percent of the time. This indicates that tongue rolling may also be controlled by the environment.

True: If identical twins are genetically identical but do not share a trait, the environment may likely be playing a role in the expression of that trait. Although not mentioned in this chapter, environmentally induced epigenetics/gene expression may play a role as well.

The research done by Soto, Sonnenschein, and Hunt reveals how chemicals could affect the production of gametes, thereby affecting the passage of genetic traits down from one generation to the next. Which of the following mechanisms are responsible for the generation of genetically diverse offspring?

crossing over independent assortment of chromosomes during meiosis I genetic recombination

In 4 o'clock flowers, flower color is controlled by a single gene with two alleles. The R allele produces red flower color, and the W allele produces white flower color. These alleles display incomplete dominance, and when both alleles are present, the flowers appear pink. Remember, when dealing with incomplete dominance, only capitals are used for the two traits because neither allele exerts dominance over the other. Match each of the following genotypes to the correct color of flowers. RF

homozygous RR

In 4 o'clock flowers, flower color is controlled by a single gene with two alleles. The R allele produces red flower color, and the W allele produces white flower color. These alleles display incomplete dominance, and when both alleles are present, the flowers appear pink. Remember, when dealing with incomplete dominance, only capitals are used for the two traits because neither allele exerts dominance over the other. Match each of the following genotypes to the correct color of flowers. WF

homozygous WW

Most women have their cervical cells screened as part of their routine pap exam. The doctor looks at the cervical cells to determine if they appear normal or are abnormal. Which of the following could signify an abnormal cell?

increased size arrest of normal functions change in shape

Two people of medium skin tone have five children, each with a different skin tone ranging from very pale to very dark. Most of the children's skin becomes a little bit darker after exposure to the sun. Judging from this information, skin tone is probably what?

influenced by the environment a polygenic trait

Which of the following traits are Mendelian and which show more complex patterns of inheritance? Complex

intelligence in humans coat color in Labrador dogs body size in humans

Soto and Shonnenschein finally identified nonylphenol in the flasks they were using. Nonylphenol can do which of the following?

interfere with the G0/G1 checkpoint activate mitotic division

Occasionally, a gamete is formed that contains both alleles of a gene instead of one. The result is the presence of three alleles of a gene after fertilization. Which of Mendel's laws would this gamete violate, and when during meiosis would the gamete form?

law of segregation, meiosis I

The human genome has an estimated 25,000 genes on 23 chromosomes that can be affected by crossing-over and assorted into gametes. Given these numbers, about how many different combinations of chromosomes may be found in the gametes?

millions

The fur color of Siamese cats is partly controlled by temperature. Where their skin is relatively cool, like their ears, their fur grows dark, and where their skin is warmer, like their torso, their fur grows white. In this example, temperature is affecting what aspect of the Siamese cat?

phenotype