Genetics Exam 4
explain why duplication is a driving force for evolution and the generation of new genes.
-Duplicated genes provide extra copies of DNA that are not constrained by an essential function. -Genes duplicate and then diverge from the original sequence to create novel genes. -Phenotypic variations can occur when random fixed mutations are introduced into a new chromosomal environment.
Genetic Material Possesses Several Key Characteristics
1. The genetic material must contain complex information 2. The genetic material must replicate faithfully 3. The genetic material must encode the phenotype 4. The genetic material must have the capacity to vary
Enter the complementary sequence to the DNA strand shown. 5′- CGATGAGCC -3′
3' - GCTACTCGG-5'
Suppose that a B‑DNA molecule has 8.4×106 nucleotide pairs. Calculate the number of complete turns there are in this molecule.
8.4*10^5
polyploidy
A chromosomal complement with at least three complete sets of homologous chromosomes
Which of the following single-stranded DNA sequences is most likely to form a stem-loop structure?
AGGAGCACTGGCTCCT
Nucleosome
Basic repeating unit of chromatin, consisting of a core of eight histone proteins
Which of these is an example of a sequence of bases in an RNA molecule that will produce a hairpin structure? Select all that apply.
CGCGCAAAGCGCG UGCGAUACUCAUCGCA
Monosomy
Chromosomal abnormality consisting of the absence of one chromosome from the normal diploid number
displaced duplication
Chromosome rearrangement in which the duplicated segment is some distance from the original segment, either on the same chromosome or on a different one.
There are two types of nucleic acids, DNA and RNA. Nearly all organisms use DNA, not RNA, as the central repository for genetic information. Choose the statements that explain this phenomenon.
DNA is more resistant against enzymes that break down nucleic acids. DNA has a double‑stranded structure that ensures an accurate mechanism of duplication.
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 condense and organize DNA.
If DNA structure is described as "beads-on-a-string," a "string" is the
DNA molecule
Identify the key structural features of a DNA molecule.
DNA strands are antiparallel and include a 5′ end and a 3′ end. DNA bases are always paired purine with pyrimidine. The backbone of DNA is made of a sugar and a phosphate molecule.
About 0.3% of human live births are trisomic. In contrast, only 0.02% of human live births are monosomic. Select the best explanation for why the occurrence of trisomics is greater than that of monosomics.
Deleterious recessive alleles may be masked by dominant alleles on trisomic chromosomes but not on the monosomic chromosomes.
Place the type of chromosomal mutation next to each set of chromosomes. This - represents the centromere. AB-CDEFG (Wild type) AB-CDE
Deletion of FG
Topoisomerase
Enzyme that adds or removes rotations in a DNA helix by temporarily breaking nucleotide strands; controls the degree of DNA supercoiling.
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%, what are the percentages of the remaining bases?
G=16% T=34% A=34%
Familial Down Syndrome
Human condition caused by a Robertsonian translocation in which the long arm of chromosome 21 is translocated to another chromosome; tends to run in families.
How do interspersed repeated DNA sequences differ from tandemly repeated DNA sequences?
Interspersed repeated DNA is derived from transposable elements, but tandemly repeated DNA is not.
key features of genetic material
It must periodically mutate to generate variation. It must be able to replicate and transmit to progeny. It must encode the blueprint to form proteins and other structures.
In 1979, bones found outside Ekaterinburg, Russia, were shown to be those of Tsar Nicholas and his family, who were executed in 1918 by a Bolshevik firing squad in the Russian Revolution. To prove that the skeletons were those of the royal family, mtDNA was extracted from the bone samples, amplified by PCR, and compared with mtDNA from living relatives of the tsar's family. Select options indicating why DNA from the mitochondria analyzed instead of nuclear DNA.
Mitochondrial DNA does not undergo recombination. Mitochondrial genomes are present in multiple copies in the cells.
A chromosomal translocation refers to
Movement of a chromosome segment to a nonhomologous chromosome
Which chromosome makeup represents the alternate segregation pattern?
N1 and N2; T1 and T2
Nalidixic acid is an antibiotic that inhibits DNA synthesis by preventing the action of DNA gyrase. DNA gyrase introduces negative supercoils into DNA. Which statements explain why inhibiting negative supercoiling in bacteria inhibits overall bacterial growth?
Negative supercoiling aids in DNA synthesis by making separation of the DNA strands possible. Negative supercoiling aids in chromosome compaction, which ensures the transmission of chromosomes to daughter cells.
Arrange the features of eukaryotic chromosome packaging in order from the smallest unit to the largest unit. chromosome, coiled fiber, genome, nucleotide, nucleosome
Nucleotide Nucleosome Coiled fiber Chromosome Genome
uniparental inheritance
One parent transmits all genetic information to all offspring
Place the type of chromosomal mutation next to each set of chromosomes. This - represents the centromere. AB-CDEFG (Wild type) AB-CGFED
Paracentric inversion of DEFG
Place the type of chromosomal mutation next to each set of chromosomes. This - represents the centromere. AB-CDEFG (Wild type) ACDE-BFG
Pericentric inversion of BCDE
Homoplasy
Presence of only one version of DNA within the cytoplasm of a single cell
heteroplasmy
Presence of two or more distinct variants of DNA within the cytoplasm of a single cell
Which of the statements describes purines and pyrimidines in DNA molecules?
Purines form hydrogen bonds with pyrimidines. Purines consist of a two-ring structure.
Place the type of translocation and sequence or sequences translocated next to each set of chromosomes. AB-CDEFG crossed with RS-TUVWX AB-TUVFG RS-CDEWX
Reciprocal translocation TUV and CDE
Place the type of translocation and sequence or sequences translocated next to each set of chromosomes. AB-CDEFG crossed with RS-TUVWX AB-CWG RS-TUVDEFX
Reciprocal translocation W and DEF
linker DNA
Small synthetic DNA fragment that contains one or more restriction sites; can be attached to the ends of any piece of DNA and used to insert it into a plasmid vector.
The antibiotics tetracycline and erythromycin inhibit bacterial protein synthesis but have no effect on proteins encoded by eukaryotic, nuclear genes. Conversely, the antibiotic cycloheximide inhibits protein synthesis of nuclear genes but has no effect on protein synthesis in bacteria. Select the statement that best describes the effect of a particular antibiotic on protein synthesis.
Tetracycline treatment would inhibit mitochondrial protein synthesis, but not protein synthesis of nuclear genes.
submeta centric
The centromere is displaced toward one end, creating a long arm and a short arm.
metacentric
The centromere is located approximately in the middle, so the chromosome has two arms of equal length.
Lesch‑Nyhan syndrome is an X‑linked, recessive condition caused by mutation of the HPRT1 gene responsible for purine metabolism. The syndrome is characterized by juvenile‑onset gout, involuntary muscle movements, and behavioral disorders. A mother and father have a young daughter who was diagnosed with Lesch‑Nyhan syndrome. No one in the father's family was ever diagnosed with the syndrome. The mother's maternal grandfather was diagnosed with Lesch‑Nyhan syndrome, but neither one of her parents was diagnosed with the condition. explain how their daughter inherited Lesch‑Nyhan syndrome
The father did not contribute a sex chromosome to his daughter due to nondisjunction of the sex chromosomes. The daughter is XO and her only X chromosome came from her mother, who was a carrier. The daughter inherited two X chromosomes with the Lesch‑Nyhan mutation. Nondisjunction of the mother's X chromosomes occurred during meiosis, and the daughter inherited no X chromosome from her father.
From which living relatives would mitochondrial DNA provide useful information for verifying that the skeletons were those of the royal family?
The mtDNA from the tsar's living relatives of maternal descent should be analyzed.
pseudodominance
The phenotypic expression of a single recessive allele resulting from deletion of a dominant allele on the homologous chromosome
What contribution did James Watson and Francis Crick make to our understanding of DNA?
They modeled the structure of DNA based on the limited data available.
euploidy
a complete set or an exact multiple of the haploid chromosome set
Trisomy
a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities.
Which segregation pattern results in viable gametes?
alternate segregation
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
By the time that meiosis is completed in an individual heterozygous with paracentric inversion, there __ viable gamete or gametes produced.
are two
Histone proteins
attach to DNA and form compacted DNA-protein associations.
Why could reciprocal translocation result in nonviable gametes?
because some chromosome segments are presented in two copies whereas others are missing
How does chromosome compaction differ during metaphase and interphase in eukaryotes?
chromosomes are less compacted in interphase than in metaphase
What is the key feature of DNA that allows it to be copied?
complementary base pairing
Which structure is characteristic of a heterozygous chromosome with an inversion?
dicentric bridge
Place the type of chromosomal mutation next to each set of chromosomes. This - represents the centromere. AB-CDEFG (Wild type) AB-DEFCDEFG
displaced duplication of DEF
positive supercoiling
double helix is overwound
negative supercoiling
double helix is underwound
reverse duplication
duplication of a chromosome segment in which the sequence of the duplicated segment is inverted relative to the sequence of the original segment
The less condensed form of chromatin is
euchromatin
endosymbiotic theory
explains why mitochondria contain their own genetic information states that an ancestral eukaryotic cell engulfed an aerobic protobacteria explains the origin of some eukaryotic organelles, such as chloroplasts
what helical structure is DNA?
form B
Tetrasomy
gain of two homologous chromosomes
a single unpaired copy of each chromosome
haploid
acrocentric
he centromere is near one end, producing a long arm and a knob, or satellite, at the other end.
The inactive form of chromatin is
heterochromatin
The more darkly-staining form of chromatin is
heterochromatin
A core composed of________ proteins interacts with DNA through hydrogen bonding and ionic bonds.
histone
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 mother in meiosis II
Consider the diagram. AB∙CDEFG>AB∙CFEDG AB∙CDEFG>AB∙CFEDG Which chromosomal abnormality is represented in the diagram?
inversion
During meiosis, errors can be made during chromosome replication. Which term describes a mutation where a chromosome breaks, and its genetic material is reinserted in a different orientation?
inversion
Nullisomy
loss of both members of a homologous pair of chromosomes (2n-2)
Examples of genetic material that are uniparentally inherited in sexually reproducing eukaryotes
mitochondria and chloroplasts
only one copy of a specific chromosome
monosomic
a genome composed of one unique chromosome
n=1
Place the type of translocation and sequence or sequences translocated next to each set of chromosomes. AB-CDEFG crossed with RS-TUVWX AB-CD RS-TUVWXEFG
non-reciprocal translocation of EFG
Place the type of translocation and sequence or sequences translocated next to each set of chromosomes. AB-CDEFG crossed with RS-TUVWX AUVB-CDEFG RS-TWX
non-reciprocal translocation of UV
Many errors can occur during meiosis. Which term describes the process of sister chromatids not separating at the centromere during cell division?
nondisjunction
If DNA structure is described as "beads-on-a-string," a "bead" is a
nucleosome
________ is a DNA-protein complex.
nucleosome
Consider the diagram. AB∙CDEFG>AB∙CFEDG AB∙CDEFG>AB∙CFEDG Which type of inversion is presented in the diagram?
paracentric
Consider the diagram. AB∙CDEFG>ABC∙BEFG AB∙CDEFG>ABC∙BEFG Which type of inversion is presented in the diagram?
pericentric
In which stage of meiosis would the chromosomes form a cross‑like configuration?
prophase I
what is the structural difference in dna and rna?
rna has an OH group on C5
James Watson and Francis Crick used this X‑ray diffraction image taken by Rosalind Franklin to deduce structural properties of B‑form DNA. What findings did Watson and Crick make from this image?
shaped like a helix, includes 10 base pairs per repeat, consistent diameter
Place the type of chromosomal mutation next to each set of chromosomes. This - represents the centromere. AB-CDEFG (Wild type) AB-CDEFDEFG
tandem duplication of DEF
aneuploidy
the addition or loss of less than a full set of chromosomes or chromosome pairs
function of the centromere in the transmission of genetic information
the attachment point for the mitotic spindle
telocentric
the centromere is at or very near the end of the chromosome
What is the likely fate of the chromosomal segment broken away from the rest of the chromosome during anaphase I?
the segment fails to separate and is lost
why does bacteria methylate their DNA?
to distinguish it from viral DNA so it is not degraded
During meiosis, errors occur during chromosome replication. Which term describes the rearranging of genetic material between non-homologous chromosomes without a net loss or gain of genetic material?
translocation
