Lecture Exam 4 Flashcards
Which of the following best describes the pattern of inheritance for mitochondrial DNA?
It is usually inherited entirely from the mother
Which of the following can directly cause genetic disease? Check all that apply.
Altering a single or multiple base pairs in the DNA of an organism
A mutation that alters a single or several amino acid within a protein
A mutation that changes a gene that codes for a normal protein into a gene that codes for a defective protein or no protein at all
Loss of a small section of a chromosome
One or more extra or missing chromosomes
During meiosis, the process of ___ produces gametes, and therefore offspring, that have extra or missing chromosomes.
nondisjunction
Gaining one extra autosome, in addition to the typical diploid number is called
trisomic
Having one or more extra or missing chromosomes is called
aneuploidy
The loss of a single autosome is called
monosomic
The affects associated with three copies of chromosome 21 are referred to as
Down syndrome
The affects associated with a single X chromosome and no Y chromosome are referred to as
Turner syndrome
The affects associated with two X chromosomes and one Y chromosome are referred to as
Kleinfelter syndrome
Female gametes with no sex chromosomes are produced when the two X chromosomes fail to ___ during meiosis
separate
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 brown-eyed female who is a carrier of colorblindness has children with a blue-eyed male who is not colorblind. The female becomes pregnant and an ultrasound test shows that the child is a male. What is the probability that he will be colorblind?
50
Suppose you are carrying out a series of crosses with an insect where the mechanism of sex determination is unknown. You discover a mutant male with black wings and decide to cross it with a wild type female that has gray wings. Half of the F1 progeny have black wings but all of these F1 progeny with black wings are females. Based on these results, a valid hypothesis would be
Females are XX, males are XY and wing scales are caused by a dominant allele on the X chromosome.
In humans, hemophilia is caused by a recessive allele on the X chromosome. Therefore, if a female with hemophilia has children with a male who doesn’t have hemophilia, the probability that their first child will be a female with hemophilia is zero. This assumes normal dosage compensation where the X that is inactivated in females varies randomly from cell to cell. But suppose the normal mechanism of dosage compensation is altered so that the X that is inactivated in any given female is random but the same X is inactivated in every cell of her body. In this case, what is the probability that their first child would be a female with hemophilia?
25
A crossover in meiosis is an exchange of genetic material between
non-sister chromatids of homologous chromosomes.
A Barr body is typically found in the nucleus of
female somatic cells only.
Random orientation of homologous chromosomes occurs in _________ of meiosis
metaphase I
Of the 23 pairs of human chromosomes, 22 pairs are homologous and are found in both males and females. These are called _________
autosomes
Traits that are controlled by genes located on the X chromosome are said to be _________
sex-linked
Allele pairs are most likely to assort independently of one another when
they are on different chromosomes.
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.
Occasionally, chromosomes fail to separate during meiosis, leading to daughter cells that have an atypical number of chromosomes. This phenomenon is called
nondisjunction.
The loss one copy of an autosome is called
monosomic
In humans, individuals with trisomy of the _________ chromosome are most likely to survive until adulthood.
21st
Hemophilia is caused by a
recessive allele on the X chromosome.
A human female with only one X chromosome is said to have a condition called
Turner syndrome.
Amniocentesis is a procedure that is normally used
for diagnosis of genetic disorders.
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 based on inheritance of the necessary sex chromosome?
In humans, the male determines the gender of the offspring, and in birds the female determines the gender.
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.
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.
The most common fatal genetic disorder of caucasians is
cystic fibrosis.
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 the fruit fly Drosophila, the gene “T” for tan body color is dominant to the allele “t” for ebony body color. At another gene locus on the same chromosome the allele “B” for normal bristles is dominant to the allele “b” for short bristles. Two flies are crossed that both have the same genotype: the alleles “T” and “B” are on one chromosome and the alleles “t” and “b” are on the homologous chromosome. If we assume that no crossing over occurs between these two gene loci, what is the expected phenotypic ratio among the offspring?
3:1
During bacterial transformation, one or more traits of a cell are altered due to the uptake of DNA from the surrounding environment.
True
Avery, MacLeod, and McCarty were the first scientists to describe the process of bacterial transformation.
False
Griffith determined that DNA is the substance responsible for bacterial transformation.
False
During Griffith’s experiments, a nonvirulent form of S. pneumoniae was transformed into a virulent form.
True
During their experiments, Avery, MacLeod, and McCarty discovered that the removal of nearly all protein from their preparation destroyed its transforming activity.
False
Which characteristic of DNA allows each strand of the molecule to act as a template that specifies the exact sequence of nucleotides in the other strand?
Complementarity of the bases
If 28% of the nucleotides in a DNA molecule contain the base T, what percent will contain the base G? (Enter your answer as a whole number without the percent sign. For example, 5% would be entered as 5 and 37% would be entered as 37)
22
Because the two strands of a DNA molecule are _________blank to each other, either one can be used as a template to reconstruct the other.
complementaryCorrect
DNA consists of two antiparallel strands of nucleotides held together by
hydrogen bonds.
creates a short RNA primer that is complementary to a DNA template.
DNA primase
Chargaff’s rules for the pairing of nitrogen bases is
A = T and G = C.
Information obtained by Franklin from X-ray crystallography on DNA suggested that it is shaped like a
helix
The site where the two original DNA strands separate and active replication occurs is called the
replication fork.
During DNA replication, DNA pol III synthesizes the lagging strand in segments, called
Okazaki fragments.
During replication, which enzyme unwinds the DNA double helix?
DNA helicase
If we think of the DNA double helix as a twisted ladder, what makes up the rungs or steps of the ladder?
Purines and pyrimidines
Viruses that attack bacteria are called
phages
Which enzyme adds new nucleotides to the end of a growing strand?
Polymerase
When a mixture of live nonvirulent bacteria and dead virulent bacteria was injected into mice, Griffith unexpectedly found that the injected mice died. He explained this result by suggesting that the nonvirulent bacteria are being
transformed
Nucleotides have a phosphate group attached at the _________blank carbon atom of the sugar.
5’
The lagging strand is replicated with a series of Okazaki fragments and that is why its synthesis is considered to be
discontinuous.
Who proposed that the structure of DNA is a double helix with two polynucleotide chains running in opposite directions and held together by hydrogen bonding between pairs of nitrogenous bases?
Watson and Crick
Who demonstrated that phage genetic material is DNA and not protein?
Hershey and Chase
If a mutation produced helicase that was unable to hydrolyze ATP, DNA replication would be
stopped
The correct structure of DNA monomers can be presented as
phosphate–sugar–base.
Arrange the following proteins in the proper order in which they participate in DNA replication.
1 = Primase
2 = Helicase
3 = Single-strand binding proteins
4 = DNA polymerase I
Helicase
Single strand binding proteins
primase
dna polymerase I
DNA affects the traits of an organism by providing the instructions for synthesizing _________blank.
proteins
Gene expression involves two phases, _________blank and translation.
transcription
Messenger RNA molecules contain information that is used to synthesize _________blank.
polypeptides
To begin transcription, RNA polymerase must bind to a segment of DNA called the _________blank.
promoter
The strand of DNA that is not transcribed is called the _________blank strand.
coding
Crick, Brenner, and their colleagues proposed that the genetic code consists of a series of blocks of information, called _________blank, each corresponding to one amino acid in an encoded protein.
codonsCorrect
During transcription of mRNA in eukaryotes, some sequences are cut out of the primary transcript and the remaining sequences are joined together. This processing of mRNA is called _________blank.
splicingCorrect
The polypeptide-making organelles, which consist of protein combined with RNA, are called
ribosomes
Which base in an anticodon will pair with the base adenine in a codon?
UracilCorrect
The A, P, and E sites are progressively occupied by amino acids being assembled into a polypeptide. These sites are part of
the large ribosomal subunit.
In eukaryotic cells, transcription occurs
inside the nucleus.
How many unique mRNA codons can be constructed from the four different RNA nucleotides?
64Correct
Eukaryotic mRNA molecules may contain noncoding sequences that must be removed before translation. These are called
introns
In eukaryotes, pre-mRNA processing may involve all of the following except
removal of exons from the pre-mRNA.
The Central Dogma of biology can be stated as
DNA→ RNA→ Proteins.
What is the first step during transcription initiation in prokaryotes?
RNA polymerase binds to the promoter
RNA polymerase binds to a region of the DNA called the
promoter
begins to unwind and separate the 2 strands of the DNA double helix.
RNA polymerase
Actual synthesis of the RNA transcript begins at the
start site
Successive RNA nucleotides are added to the 3’ end of the growing RNA chain during a process called
elongation
When RNA polymerase reaches a ___, the RNA transcript and RNA polymerase separate from the DNA, and the DNA within the transcription bubble rewinds.
terminator sequence
The principle of colinearity of genes and proteins does not apply to eukaryotes because
most eukaryotic genes contain introns.
