Biology Test 3
Assume a certain molecule of DNA is composed of exactly 22 percent adenine. How much cytosine would you expect to find in this molecule?
28%
The genetic code is made of codons that are
3 bases long
A pea plant that is heterozygous for the flower color gene makes gametes. What is the probability that a specific gamete contains the recessive allele for flower color?
50 percent
Consider a gene with two alleles that show complete dominance. When a homozygous recessive individual is crossed with a heterozygous individual they have a 50% change of producing a homozygous recessive offspring. The next time these same two individuals breed, what are the chances that they will once again have a homozygous recessive progeny?
50%
Consider a complete, functional piece of mRNA that contains a total of 66 codons. What is the maximum number of amino acids that could be present in the protein coded for by this mRNA?
65
If a PCR reaction begins with a single DNA double helix, how many copies will there be after three cycles?
8
Which of the following would explain two chromosomes in an individual cell that contain some, but not all, of the same genes at the same loci
A chromosomal alteration has occurred
Which of the following is an example of incomplete dominance?
A heterozygote cat has a medium-sized body instead of either large or small.
If a genetic disorder is caused by a dominant allele, individuals with which of the following genotypes would be affected by the disorder?
AA and Aa
Which of the following must be true for a woman who is heterozygous for a given gene?
All of her eggs will contain one allele or the other, but not both alleles
A gene contains the sequence GGTAAC. What is the sequence of the mRNA transcribed from this strand of DNA?
CCGAUUG
A small segment of DNA is used as a template for transcription. This contains the base sequence CGT. If an mRNA transript is made that includes this sequence, what would the anticodon on the tRNA that would bind to this corresponding mRNA sequence?
CGU
______ are points in the cell cycle where cells stop to assess their progression
Checkpoints
Which of the following statements explains how genetically identical plant clones can exhibit dramatic phenotypic variation?
Environmental conditions under which plants are grown can cause variation in phenotypes
Why are X-linked recessive genetic disorders more commonly seen in males>
Females must receive two copies of the recessive allele to exhibit the disorder, but males need only one copy
Which of the following about cell division is correct?
It is the process by which organisms grow and maintain their tissues
Which of the following statements about the process of DNA replication is false?
Mistakes in the copying process are very common occurences
What information in a pedigree would indicate a condition is likely sex-linked?
Most of the affected individuals are males
Which of the following is true for mutations?
Mutations will affect the genotype, which may affect the phenotype.
An individual with Down syndrome has three copies of chromosome 21. Would all children of an individual with Down syndrome also have Down syndrome?
No, only 50% of the eggs or sperm formed would have an extra copy of the chromosomes
Assume that you chemically label both strands within a molecule of DNA. You then allow this DNA to replicate using unlabeled nucleotides. Which of the following statements about the two resulting DNA molecules would be FALSE?
One molecule would contain the chemical label, the other would not
Which of the following choices states a correct reason why the process of cell division is different for prokaryotic that for eukaryotic cells?
Prokaryotes have a circular DNA molecule
Replication of a cell's genetic material occurs during
S phase
In a particular plant, two genes control height and flower color. Tall height (T) is completely dominant to short height (t). Yellow flowers (Y) are completely dominant to white flowers (y). A tall, yellow flowered plant is mated with a short, white-flowered plant. What are the genotypes of the plants involved in this cross?
T_Y_ x ttyy
Which of the following is true of eukaryotic genomes?
The DNA is in the nucleus of 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% chance of being affected by the disease
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
Compare and contrast the genetic code in plants and humans
The genetic code is identical for both plants and humans
If you compare a sperm cell in a human to a skin cell from the same individual, which of the following would you expect to find
The sperm cell would only contain one allele for a given gene, the skin cell would contain two alleles
The gene for a certain sex-linked trait is found only on the Y chromosome. If the male parent carries this gene, which of the following statements about the inheritance of that trait is true?
The trait will be expressed in 100 percent of the male offspring
Which of the following statements about autosomes is true?
There are 44 autosomes in humans
Which of the following statements about homologous chromosomes is true?
They contain the same genes in the same locations
What purposes do crossing over and independent assortment play in cell division?
They help to add genetic diversity to daughter cells
Which of the following is true for autosomal recessive alleles associated with a disease?
Two copies of the allele are required for the individual to be affected
Which of the following statements is NOT true?
Two organisms with the same genotype are homozygous.
A female who is a carrier of the sex-linked gene A has the genetype
X^A, X^a
A long peice of ribbon wired along both long edges is twisted into a helix and wrapped around individual pipe cleaners that have been rolled into spools; this grouping is then twisted again to condense it. This could be best used as a simple model for
a chromsome
Which of the following organisms is likely to have the least complicated form of cell division?
a disease-causing bacterium
A substitution mutation is one where
a single nucleotide is incorrect
An allele is
a version of a gene
Each set of three bases in an mRNA molecule codes for one of 20 specific
amino acids
The order of the bases in DNA determines the order of
bases in mRNA
The process of gene transcription begins with the
binding of RNA polymerase to a region of DNA called the "promoter"
A certain enzyme is known to be responsible for separating the two strands of a DNA molecule to facilitate the process of DNA replication. This enzyme most likely
breaks hydrogen bonds between bases
Sister chromatids are held together at a region called the
centromere
Mutations are aleays
changes in the DNA sequence
If two different alleles for the same trait have an equal effect on the phenotype, the alleles are
codominant
In humans, the presence of an SRY gene
commits a developing embryo to male.
Some daughter cells are descibed as clones. For this description to be appropriate, the daughter cells must
contain a set of DNA that is identical to that of the parent cell
What is the primary role of DNA polymerase?
copy a single strand of DNA
Which of the following processes divides the cytoplasm of the cells following mitosis?
cytokinesis
Which of the following factors might cause a cell to pause in a phase of the cell cycle?
damage to DNA
Bacteria produce proteins that bind to the promoter and block RNA polymerase from binding to structural genes. An increase in production of repressor will
decrease transcription of the structural gene
The structure highlighted in the figure below corresponds to a
duplicated chromosome
A sequence of DNA that contains information for the synthesis of RNA molecules used in the manufacture of proteins is also known as a
gene
In Mendel's model of inheritance, what he described as units of inheritance we now refer to as
genes
Which of the following statements regarding genes is true
genes are the basic units of information affecting a genetic trait
If a person has one copy of each of two different alleles for a given gene, the person is __________ for that trait
heterozygous
During crossing over
homologous chromosomes exchange genetic information
Which of the following statements regarding gene is NOT true?
in sexually reproducing species, each somatic cell contains a single copy of every gene
Being able to us a Punnett square to track the pattern of inheritance in a two-characteristic cross demonstrates Mendel's idea of
independent assortment
For the information contained in a gene to be used to produce a functioning protein
information must be transcribed into mRNA and then translated into amino acids
Even though you and your brothers or sisters are all humans, odds are that each of you has a somewhat different genetic makeup. The molecular basis for this inherited variation
is related to the difference in there DNA nucleotide sequence of your genes
The chance of a parent passing on a given allele to a child ________ each time he or she has another child.
is the same
A biologist intends to use PCR to perform a task. The biologist probably is trying to
make many copies of a DNA fragment
Mendel's breeding experiments with pea plants indicate that alleles of a gene separate during
meiosis
During which of the following phases of mitosis do replicated chromosomes line up at an invisible plane along the center of the cell?
metaphase
The form of eukaryotic cell division that produces two genetically identical cells is
mitosis
The second division of meiosis is essentially
mitosis that begins with two haploid cells and ends with four haploid cells
Based on the figure below, a complete cell cycle consists of which of the following phase?
mitosis, G1 phase, S phase, and G2 phase
The Y chromosome in humans is
normally found in a single copy
Which of the following parts of a DNA molecule are held together by hydrogen bonds
nucleotide bases on opposite strands of the double helix
Genetic carriers are individuals who carry
one copy of a recessive mutated allele and one normal copy.
Most traits in humans are controlled by the action of multiple genes. These traits are referred to as
polygenic
Which is NOT a component of a nucleotide?
primer
Prokaryotes lack membrane-enclose organelles and thus do not have nuclei. Therefore
prokaryotic transcription and translation both take place in the cytoplasm
Without the ________ site on a molecule of DNA, _________ cannot bind to the DNA to begin the process of _________
promoter, RNA polymerase, transcription
The nuclear envelope breaks down during which phase of mitosis?
prophase
Most inherited human disorders are the result of
recessive mutations of genes located on autosomes
Consider the 3-D structure of DNA. Which of the following has a structure analogous to a molecule of DNA?
spiral staircase
Which of the following genetic changes would be passed from parent to child?
the addition of a chromosome in an egg cell
A mutation to the tRNA changes the amino acid bound to the tRNA with the anticodon of AGG from serine to alanine. How will this affect the cell?
the cell will add the wrong amino acid when mRNA has the codon UCC
Two pea plants that are true-breeding for recessive white flowers are mated and their offspring analyzed. Which of the following statements about this situation is true?
the gametes produced by the offspring will carry only one allele for this gene
An uncorrected error during human DNA replication can result in
the potential for a disease or genetic disorder
The most important characteristic that distinguishes meiosis from mitosis is
the total number of chromosomes present in daughter cells
Which of the following explains why a cell might undergo meiosis?
to produce egg and sperm cells
An organism that has more than the usual number of mutations likely has
too few repair enzymes
If you expose a cell to chemicals that specifically disrupt the function of RNA polymerase, which of the following processes will be most directly affected?
transcription
Which of the following does NOT take place in the nucleus
translation
In a karyotype of a female, which of the following would indicate a normal karyotype?
two X chromosomes
A replicated chromosome consists of
two sister chromatids
A gene responsible for producing an enzyme that is used to make tryptophan in bacteria. If the cell has enough tryptophan and doesn't need any more, it would most likely
use an inhibitor to block the RNA polymerase from binding to the promoter
