Genetics (Ch. 6, 7, 8, 10, 11) HW/Quiz Questions

Select each of the characteristics that are key features of genetic material.

-It must be variable through infrequent mutation. -It must be able to replicate and transmit to progeny. -It must be able to store and express information.

Enter the complementary sequence to the DNA strand shown. 5′- GCATTCAAG -3′

3′-CGTAAGTTC-5′

Suppose the data in the table is collected for an unknown nucleic acid. Identify the unknown nucleic acid.

single‑stranded RNA

Which of the statements cannot occur with X‑linked dominant inheritance for a rare trait?

An affected man can pass on the trait to his son.

Which statement is the definition of a map unit (centimorgan)?

It is the percent chance of a recombination between two locations on a chromosome.

Most of the centromere and telomere structures consist of

heterochromatin

Which of the statements describes purines and pyrimidines in DNA molecules?

-Pyrimidines consist of a one-ring structure. -Pyrimidines form hydrogen bonds with purines.

What does the term antiparallel mean?

-The strands run in opposite directions. -The 5' end of one strand is opposite the 3' end of the second strand.

What is a purine? Select all that apply.

-a base with two rings -adenine or guanine

A key discovery leading to the structure of DNA was done by Chargaff. He found that ____. Select all that apply.

-the tetranucleotide hypothesis was false -the amount of A equals the amount of T, and the amount of G equals the amount of C

Use the information gathered in the Determining Gene Order by Three‑Point Cross animation to answer the question. How many different types of gametes could be produced by the triple mutant male parent?

1

Use the information gathered in the A Three Point Test Cross animation to answer the question. The recombination frequency between genes A and B is 23%.23%. What is the distance between A and B in map units?

23 m.u.

A recombination frequency of 5% translates to what distance on a genetic map?

5 m.u.

A genetic cross with two genes produces 400 offspring, and 20 of them have recombinant phenotypes. What is the recombination frequency for this cross?

5%

If a man exhibits a Y‑linked trait, what proportion of his sons should also be affected?

> all one‑fourth none one‑half three‑fourths

Which statement about chromosome inversions is correct?

Chromosome inversions flip a segment of a chromosome 180 degrees.

How does chromosome compaction differ during metaphase and interphase in eukaryotes?

Chromosomes are less compacted in interphase than in metaphase.

DNA is wrapped around histone proteins and coiled to form a dense fiber called chromatin. Which statement describes the function of the chromatin conformation of DNA?

DNA is wrapped around histone proteins to regulate gene expression.

DNA has unique properties that allow it to accurately retain genetic information, even after multiple rounds of replication. One aspect of DNA that allows it to accurately store genetic information is the base pairing from Chargaff's first rule of the four nucleotide bases. If the C content of a DNA molecule is 16%,16%, what are the percentages of the remaining bases?

G=16% T=34% A=34%

Which statement explains why the recombination frequency between two genes is always less than 50%?

Genes with a recombination frequency near 50% are unlinked and have an equal likelihood of being inherited together or separately.

Which statement best describes linkage?

It is a condition in which two or more genes do not show independent assortment.

Which statement about cellular DNA in incorrect?

Most cellular DNA is positively supercoiled.

When two genes are linked but quite far apart, their estimated map distance, based on recombination frequencies, is often an underestimation of their true map distance. What is the explanation for this underestimation?

Some double crossover events go undetected since they do not lead to recombinant progeny.

Select the function of the centromere in the transmission of genetic information.

the attachment point for sister chromatids

In a testcross involving two heterozygous genes, equal numbers of recombinant and nonrecombinant progeny are produced. From this result, what can be concluded?

The genes are not linked.

What information about recombination frequencies enables scientists to create linkage maps?

The higher the recombination frequency, the farther apart two genes are on a chromosome.

Which of the statements about X‑linked recessive traits is false?

They can be passed from father to son.

Which statement about Down syndrome is true?

Trisomy of chromosome 21 is well tolerated enough to give rise to fully‑developed individuals.

Albinism is a recessive trait that prevents an animal from being able to produce certain pigments. Snowflake is the albino gray squirrel in the image.

What is Snowflake's genotype? -gg Based on Snowflake's genotype, what is the genotype of squirrel D? -Gg

Which statement about aneuploidy is true?

`One form of aneuploidy is a loss of both members of a homologous pair of chromosomes.

Select the definition of euploidy.

a complete chromosome set or an exact multiple of the haploid chromosome set

A structure formed by a single‑stranded DNA or RNA molecule that has complementary sequences is

a hairpin.

A strong covalent bond between adjacent nucleotides is

a phosphodiester bond.

Red‑green color blindness is a human X‑linked recessive disorder. The normal allele, XB, is dominant to the mutant allele, Xb. Jill has normal color vision, but her father is color blind. Jill marries Tom, who also has normal color vision. Jill and Tom have a daughter who has Turner syndrome and is color blind. How and from whom did the daughter inherit color blindness?

an ovum carrying Xb followed by fertilization by sperm from a paternal nondisjunction event

Histone proteins

associate with DNA and compact DNA within the nucleus.

Two brothers have X‑linked red-green colorblind vision, and their parents have normal color vision. The first brother's karyotype is 47,XXY (Klinefelter syndrome), and the second brother's karyotype is 46,XY. In which parent and in what cell division phase did the first brother's chromosomal nondisjunction occur? Assume no recombination.

in the mother in meiosis II

The sugar in DNA is called "deoxyribose" because it

is missing a 2'−OH−OH group.

Use the karyotype interactive to answer the question. Aneuploidy is an umbrella term referring to multiple kinds of conditions in which an individual has an abnormal number of chromosomes for their species. Some of the patients on the abnormal tab of the karyotype virtual interactive suffer from different types of aneuploidy. Use the interactive to determine from which form of aneuploidy patient 367 suffers.

monosomy

Failure to separate for homologous chromosomes or sister chromatids is referred to as

nondisjunction

Many errors can occur during meiosis. Which term describes the process of sister chromatids not separating at the centromere during cell division?

nondisjunction

Additional copies of a gene ___ cause cellular problems.

sometimes

The number of hydrogen bonds between complementary G−CG−C pairs is

three.

Of all cases of primary Down syndrome, 92% is due to of Chromosome 21.

trisomy

Suppose a geneticist is using a three‑point testcross to map three linked Drosophila recessive mutations called s, z, and b, where s is associated with abnormally slow movement, z is associated with zigzag movement pattern, and b is associated with broad wings. The geneticist first crosses homozygous broad flies to homozygous slow, zigzag flies. Next, he testcrosses the F1 progeny to slow, zigzag, and broad parents and obtains the results in the table.

- zbs - sbz

In 1953, the scientists James Watson and Francis Crick published their landmark findings on the structure of DNA. Watson and Crick deduced the structure of DNA by unifying evidence that they collected from several scientists who were also seeking to answer this important question. Identify the pieces of evidence describing the features of DNA that Watson and Crick used to determine the structure of DNA.

-A purine base forms hydrogen bonds to pair with a pyrimidine base located on the opposite DNA strand. Specifically, A pairs with T, and C pairs with G. -The diameter of the DNA double helix is 2 nanometers, with each purine-pyrimidine base pair spanning an equivalent distance between the two chains. -The sugar-phosphate backbones of each DNA helix run antiparallel to one another. -The nitrogenous bases on each DNA helix are arranged perpendicularly to the central axis.

Which statements about euchromatin and heterochromatin are correct?

-Euchromatin undergoes condensation and decondensation throughout the cell cycle. -The majority of transcription takes place on euchromatin.

Identify the key structural features of a DNA molecule.

-The backbone of DNA is made of a sugar and a phosphate molecule. -DNA strands are antiparallel and include a 5′5′ end and a 3′3′ end. -DNA bases are always paired using Watson-Crick base pairing.

An analysis is performed to determine the proportions of each of the four nucleotide bases in the DNA of several tissue samples from various species. The results appear in the table. Which conclusions can be drawn from this data?

-The proportion of T is roughly equal to the proportion of A. -The proportion of G is roughly equal to the proportion of C. -The proportion of pyrimidines is roughly equal to the proportion of purines.

Use the information gathered in the Determining Gene Order by Three‑Point Cross animation to answer the question. How many different types of recombinant gametes could be produced by the wild‑type female parent heterozygous for all three mutations?

6

Red-green color blindness is an X‑linked recessive trait. Heterozygous females have normal color vision but are carriers of the allele for red-green color blindness. Based on the information presented in the pedigree, select all of the females that are known carriers of red-green color blindness.

Based on the information presented in the pedigree, select all of the females that are known carriers of red-green color blindness. 2 10 23

John and Sue are expecting a child, but are concerned about a rare autosomal recessive disease that is present in both of their families. In the pedigree, John is represented as individual III‑11 and Sue is represented as individual III‑12; both are unaffected. John's sister, III‑10, and Sue's brother, III‑13, both do not show evidence of the disease, but John's paternal grandmother and Sue's maternal grandfather both had the disease. Assign the appropriate symbol to each individual in the pedigree.

What is the probability that John is a carrier? probability: %66.7 What is the probability that neither John nor Sue is a carrier? probability: %16.6

Use the information gathered in the Determining Gene Order by Three‑Point Cross animation to answer the question. Could gene order be determined if rather than eight phenotypes of progeny, as seen in the animation, there were only six phenotypes of progeny observed, representing three reciprocal progeny groups?

Yes, it can be, assuming that the double recombinants are the two types of predicted progeny that are missing and that there are zero of each type.

The major contribution of Franklin and Wilkins to the study of DNA was

an X‑ray diffraction pattern.

What is a proband?

an affected individual in a pedigree who brings the family to the attention of the medical community

A pedigree of a family with a rare genetic disorder is shown. Use the pedigree to determine the mode of inheritance of the disorder.

autosomal dominant

Use the information gathered in the Interpretation of a Pedigree animation to answer the question. Consider the list. usually appears in both sexes with equal frequency both parents can transmit the trait to their offspring affected offspring most commonly have an affected parent unaffected parents do not transmit the trait does not skip generations Which of the inheritance patterns best fits the pedigree characteristics described in the list?

autosomal dominant

In the pedigree is a family with a rare genetic disorder. Use the pedigree to determine the mode of inheritance of the disorder.

autosomal recessive

What is the key feature of DNA that allows it to be copied?

complementary base pairing

Use the information gathered in the Crossing Over in an Individual Heterozygous for a Paracentric Inversion animation to answer the question. Which structure forms as a result of a crossover between two paired chromatids in which one chromatid has the normal gene order and the other has a paracentric inversion?

dicentric bridge

Three‑point testcrosses are often used to map genes. The two least frequent classes from such crosses usually represent which types of progeny?

double‑crossover progeny

The spread of a complete metaphase chromosome set presented for diagnostic purposes is called a .

karyotype

The image portrays a representation of a human karyotype. What type of genetic disorder is shown in this karyotype?

monosomy

A male with a rare autosomal dominant trait marries a phenotypically normal woman. What proportion of their children should show the trait?

one‑half

Use the information gathered in the Crossing Over in an Individual Heterozygous for a Paracentric Inversion animation to answer the question. Consider the diagram. AB∙CDEFG>AB∙CFEDGAB∙CDEFG>AB∙CFEDG Which type of inversion is presented in the diagram?

paracentric

Consider the set of crosses for hypothetical genes that control eye color and tail length in mice. Diane is working with mice with recessive mutations for the genes that control light eye color (b) and short tail length (t). She knows that these genes display genetic linkage and are found on chromosome III. In her work, she crosses a true‑breeding male with light eyes and a long tail (bbTT) and a true‑breeding female with dark eyes and a short tail (BBtt). She then crosses the resulting heterozygous progeny (BbTt) together in a dihybrid cross. The number of animals of each phenotype of this second cross is shown. dark‑eyed, short‑tailed (𝐵𝐵𝑡𝑡)=24dark‑eyed, short‑tailed (BBtt)=24 dark‑eyed, long‑tailed (𝐵𝑏𝑇𝑡 or 𝐵𝐵𝑇𝑇)=53dark‑eyed, long‑tailed (BbTt or BBTT)=53 light‑eyed, long‑tailed (𝑏𝑏𝑇𝑇)=22light‑eyed, long‑tailed (bbTT)=22 light‑eyed, short‑tailed (𝑏𝑏𝑡𝑡)=3light‑eyed, short‑tailed (bbtt)=3 What is the most likely explanation for why Diane sees light‑eyed, short‑tailed (bbtt) progeny in this cross?

recombination

Which term describes the tertiary structural organization of chromosomal DNA that allows the long strand to be packed and fit into the cytoplasm of the cell?

supercoiling

During meiosis, errors occur during chromosome replication. Which term describes the rearranging of genetic material between nonhomologous chromosomes without a net loss or gain of genetic material?

translocation

In Avery, MacLeod, and McCarty's experiments, homogenates from heat‑killed bacteria were treated with different enzymes, and then the ability of those homogenates to transform bacteria was assayed. Under which condition would transformation not occur?

treatment with DNase

Use the information gathered in the Levels of Chromatin Structure animation to answer the question. The protein composition of the nucleosome is

two copies each of histones H2A, H2B, H3, and H4.