155 terms


Why is Gregor Mendel considered the Father of Genetics?
He was the first to devise the basic laws of genetics.
On what organism did Mendel perform his genetic experiments?
the pea plant Pisum sativum
What did Mendel do to control for certain attributes in his pea plants?
He used a paintbrush to control which plants would pollinate others.
Let's say that blue flowers are dominant and red flowers are recessive. If you crossed a true-breeding blue plant to a true-breeding red flower, what would the outcome be?
blue flowers
Which of the following is one of the key results that Mendel described?
Characteristics do not simply "blend" over generations.
Which peas maintained their phenotypes over generations.
yellow and green pea
In Mendel's classic experiments with pea color, what ratio of yellow seeds to green seeds did he see in the F2 generation?
The offspring of two successive crosses are referred to as _____.
Which of the following was a key aspect of Mendel's method that set him apart from other experimenters?
his careful counting of the offspring of his crosses
What is an allele?
a form of gene
Suppose a plant heterozygous for each gene is self-fertilized, and 1,000 offspring are produced. How many plants would Mendel have expected to be dwarf with purple flowers and wrinkled, one-pod seeds?
The probability of getting dwarf = 1/4, purple = 3/4, wrinkled = 1/4, and one-pod seeds = 3/4. 1/4 × 3/4 × 1/4 × 3/4 = 9/256 (1,000) ≅ 35.
What is the expected phenotypic ratio of a monohybrid cross if both parents are heterozygous for a particular trait?
Having six fingers is dominant, and having five fingers is recessive. If a person has six fingers, what is her genotype?
homozygous dominant or heterozygous
A couple wants to have three children, and all of them be daughters. What is the probability that this will actually occur?
Dominant alleles that cause fatal conditions are less common than recessive alleles that cause fatal conditions. Which of the following statements explains why this is so?
Every person carrying a single fatal dominant allele dies, whereas most individuals who carry a single recessive lethal allele live and reproduce.
A and a are dominant and recessive alleles, respectively, of the same gene. Which genotype(s) would result in an individual with the recessive phenotype?
only aa
If a disease is caused by a recessive allele, it means that a person with the disease _________.
can pass it on to children if the person's mate also carries the allele
The allele F codes for the presence of freckles, whereas the allele f codes for the absence of freckles. The ________________ of a person with freckles could be FF, and an individual without freckles would be __________________ recessive for this trait.
genotype; homozygous
Dimpled cheeks (D) are dominant to undimpled cheeks (d). If a child has a 25% chance of having undimpled cheeks, the parental genotypes must be ___________.
Dd and Dd
A plant that produces white flowers is crossed to a plant that produces orange flowers. If all the offspring produce orange flowers, what can you conclude?
The orange flower is the dominant phenotype.
The allele R causes a genetic disease. The normal allele is denoted as R. Your genotype is RR. You will have the disease if ____________.
the R* allele is dominant
What would you expect the phenotype of a Bb type organism to be? Allele B is completely dominant to the b allele.
the same as a BB organism
What would be the expected phenotypic ratio of the F2 generation if in the P generation a homozygous dominant male black hamster is crossed with a homozygous recessive female white hamster?
For Mendel's pea plants, tall (T) is dominant over dwarf (t), and purple flowers (P) are dominant over white flowers (p). Assuming that these genes sort independently, how many different types of gametes would be produced in a plant with the genotype TtPP?
When Mendel crossed heterozygotes for flower color and seed color, what proportion of the offspring had both recessive phenotypes?
If two different traits resided on the same chromosome, which of Mendel's laws would these traits break?
the law of independent assortment
In a dihybrid cross, what ratio of double recessive organisms to others would you expect to find?
For Mendel's pea plants, tall (T) is dominant over dwarf (t), and purple flowers (P) are dominant over white flowers (p). A plant that has a phenotype of dwarf plant and white flowers has which genotype?
A diploid cell with a total of four chromosomes is heterozygous at 10 different genes. Do the genes assort independently during meiosis?
No, the genes do not sort independently.
You have become a renowned marine biologist. In your travels, you discover a species of fish that is diploid and reproduces exactly like other sexually reproducing animals, with the exception that this animal is hermaphroditic (it has both male and female reproductive organs and can self-fertilize). You mate two fish and then raise one of their offspring and allow it to self-fertilize, producing hundreds of offspring. Which of the following statements about the offspring of the self-fertilizing fish is true?
They have the same genes as their parent, but the alleles are shuffled into different combinations, resulting in phenotypically different offspring.
All seven of the garden pea traits that Mendel studied obeyed the principle of independent assortment. What does this mean?
Seven pairs of alleles determining these traits behave as if each is on separate chromosome pairs.
What is a dihybrid cross?
a cross of the F1 generation that is heterozygous for two characteristics
In another species of flowering plant, the tallness (T) trait is dominant over the dwarf condition (t), and red flowers (R) are dominant over white flowers (r). Suppose a plant heterozygous for both genes is crossed with an individual that is homozygous recessive for each trait. The cross produces a 1:1:1:1 phenotypic ratio. Are the two genes located on separate homologous pairs?
Yes. The cross TtRr × ttrr would result in the expected 1:1:1:1 phenotypic ratio if the genes assorted independently.
In the individual with genotype AaBB, what percentage of gametes will contain the B allele?
A cross between two heterozygous individuals (AaBb) at two independently assorting, incompletely dominant genes will produce an expected phenotypic ratio of __________.
In a family of six children, two are blood type O, two are blood type AB, one is blood type B, and another type A. What are the possible genotypes of the parents?
Crossing purple-flowering petunias with white-flowering petunias yields seeds that grow into petunias with lavender flowers. What does this suggest?
Incomplete dominance is occurring.
In incomplete dominance, one would observe ____.
neither allele for a particular gene being dominant
Even though incomplete dominance resembles blending, why is it NOT evidence for blending of traits?
The phenotypes of the parents return in subsequent generations.
Your neighbor cannot understand why her new flower bed contains red and white flowers. She specifically bought plants that contained only pink flowers, but as new flowers developed, some produced red and white flowers. What can you conclude?
Incomplete dominance is involved in this trait.
A mother who is heterozygous for blood type A states that a man with blood type AB is the father of her baby. If the man is indeed the father, which of the following blood types would NOT be possible for the baby to have?
type O
An individual is heterozygous for a trait that functions according to incomplete dominance. This person will exhibit _________.
an intermediate between the two phenotypes
A, B, and O blood types in humans are controlled by a single gene with three alleles: IA, IB and i. The i allele is recessive to both IA and IB. Which of the following could be possible genotypes of the parents of a person with type AB blood?
IAi and IBi
You cross a true-breeding red plant to a true-breeding white plant, and the outcome is a pink plant. What is this an example of?
incomplete dominance
A plant with orange flowers is crossed with another plant with orange flowers. The offspring show the phenotypic ratio of 1:2:1—one red flower:two orange flowers:one yellow flower. These plants are displaying a classic example of ______.
incomplete dominance
In the F2 generation (Rr × Rr) for a snapdragon, what is the expected ratio of red:pink:white phenotypes, given that RR is red, Rr is pink, and rr is white?
Which of the following is an example of polygenic inheritance?
human skin color
A child has green eyes, yet one of her parents has brown eyes, and the other has blue eyes. This can happen because human eye color is the result of ______.
polygenic inheritance
What does SNP stand for?
single nucleotide polymorphism
With respect to the effects of the environment, which of the following statements is true?
The expression of genes can vary depending upon the environment.
An allele known as BRCA1 is often found in women with breast and ovarian cancer. However, some women develop those cancers and do not have the BRCA1 allele. In addition, some women who have BRCA1 never develop breast or ovarian cancer. How can this be explained?
Something other than the allele must factor into whether cancer develops or not.
If some individuals with a particular condition all have a specific allele, and other individuals with that same allele did not necessarily develop that condition, what is the best explanation?
The condition is influenced by an environmental factor as well as the allele.
Which of the following statements correctly indicates the relationship among chromosomes, genes, and proteins?
A chromosome contains many genes that encode for proteins.
A gene is ___________.
a segment of DNA with information to code for a single protein
Consider the backbone of the DNA double helix. Which of the following statements about the structure of the double helix is FALSE?
The DNA backbone forms the central core of the DNA molecule.
What fundamental discovery in 1953 by James Watson and Francis Crick changed the way we view genes?
the structure of DNA
The elucidation of the structure of DNA answered what basic question in genetics?
how DNA carries out its genetic function
Who was the scientist whose work greatly contributed to the discovery of the structure of DNA but was not awarded a Nobel Prize for it?
Rosalind Franklin
Which of the following statements about the process of DNA replication is true?
It utilizes DNA polymerase, which catalyzes the reaction that adds a new nucleotide to the growing strand.
Which of the following statements describes a DNA molecule?
If the DNA molecule is thought of as a rigid, twisted rope ladder, the interactions of the nitrogenous bases represent the rungs of the ladder.
A single chromatid is composed of _________.
a DNA double helix
The DNA base sequence TTGCGATCG on the parent strand would code for which of the following sequences on the newly synthesized strand?
According to one of the fundamental rules of base pairings, which of the following base pairings is correct?
If you took a normal cell and replaced its thymine (T) with radioactive T and allowed that cell to divide once, which of the following results would you expect?
The DNA in each of the daughter cells would be radioactive.
A DNA sample has 20 percent C, 23 percent G, 27 percent T, and 30 percent A. This sample must have come from ________.
a single strand of DNA
DNA replication occurs at an unbelievably fast rate. Once replication is complete, a _____ number of mistakes are likely to occur.
Which of the following would indicate a base-pairing error in DNA?
a G paired with a T
A DNA template has the following base sequence: GGTCAATCG. What would be the sequence on the complementary strand?
Which of the following statements about DNA replication is FALSE?
It always produces an exact copy of the entire DNA in the cell.
A single strand of DNA is a very stable molecule. However, the two strands of the double helix are not as stable and can be separated from each other. What is the best explanation for this?
The hydrogen bonds that hold the strands of the double helix together are weak and easily broken.
A certain organism's DNA is composed of 21 percent guanine. What percentage of thymine does it have?
29 percent
A DNA sequence reads ATCGCTATCGAC. If the fourth nucleotide is changed to a T, the fourth nucleotide on the complementary strand would be _________.
DNA replication errors can be corrected by _______.
DNA polymerase
Which of the following is an appropriate base pairing?
adenine and thymine
Which of the following best describes the products of DNA replication?
one new strand of DNA and one old template strand of DNA
If you put a section of DNA in a solution with free nucleotides and the right enzyme and do a few other tricks, you can easily make billions of copies of that sequence in a matter of hours. What aspect of DNA allows for this to happen?
Each strand of DNA is a template for a new one, so it can be continually copied under the right conditions, each copy becoming a new template.
What part of DNA's structure is the most important factor for the method of its replication?
the fact that A will always pair with T and that G will always pair with C
If you were to remove the "backspacing" function in DNA polymerase, what would the result be?
Mutation rates would increase.
The nucleotides in one strand of DNA are attached to the nucleotides of another strand of DNA by _______.
hydrogen bonds between complementary bases
The parts of a nucleotide that do NOT change are the ____________.
sugars and phosphate groups
During DNA replication, each strand of the molecule acts as a(n) ______for a new strand to be made.
The "loose" bonding of two strands of DNA by hydrogen bonds allows them to _________.
be unwound
When DNA is copied, what is the arrangement of new and old strands?
Each older strand is paired with a new, complementary strand.
The error rate in DNA replication in humans is roughly _____ by the end of the process.
1/1,000,000,000 bases
While looking at the genetic makeup of a bacterium, researchers discovered that its DNA contained approximately 500,000 cytosine bases. Which of the following statements would therefore be true?
The bacterium's DNA contains 500,000 guanine bases.
During DNA replication, one template has the base sequence AACTGGCTA. What would be the sequence on the complementary strand?
If a particular gene has 23 percent cytosine, how much thymine does it contain?
27 percent
If a point mutation occurred during DNA replication, you would immediately expect to see ________.
a change to the newly synthesized DNA strand, but not the template
If ________ makes an error that is not repaired by its proofreading mechanism, a mutation will result.
DNA polymerase
The difference between two alleles is the result of _______.
the sequence of nucleotides
The types of mutations that produce new alleles and drive evolution must occur in __________.
germ cells
A point mutation ___________.
can sometimes be detrimental
Which of the following statements about gene mutations is FALSE?
They are responsible for most of the phenotypic differences between siblings.
How do mutations affect an organism?
They may cause the development of a detrimental allele or a beneficial allele, or they may have no noticeable effect.
For a mutation to play any heritable role, it must _______.
occur in a germ-line cell
If an error in base pairing becomes incorporated in the next round of replication, what is the result?
a point mutation
Given what you know about DNA replication, what is the fate of a mutation through multiple rounds of replication?
It will be faithfully be copied because it is now the template.
Most point mutations ________.
have no noticeable effect
If you accumulate enough mutations in your lungs to develop cancer, what effect will this have on your offspring?
None; somatic mutations are not transmitted through generations.
What is a mutagen?
a substance that can mutate DNA
Which of the following is an example of a mutagen?
Nearly everything has the potential to mutate DNA. - ultraviolet light, free radicals, radioactive decay
What is the most critical feature in a protein that determines its function?
its shape
How many different kinds of amino acid monomers do most organisms use to build proteins?
Which of the following plays a greater role in the great diversity of proteins?
the order of the amino acids
What distinguishes one amino acid from another?
the composition of the side chain
If you were to disrupt the process of transcription in a cell, which process would be most directly disrupted?
mRNA synthesis
How does information flow from genes to proteins?
DNA is transcribed into mRNA, which is translated into proteins by the ribosomes.
How does RNA differ from DNA?
DNA serves as a template for its own replication.
If RNA polymerase were removed from a cell, what would be the immediate effect on the cell?
RNA production would cease.
Which nitrogenous base is found only in DNA but NOT in RNA?
The RNA that carries the information to make proteins from DNA to the cytoplasm is called ____________.
messenger RNA
Transcription _______________.
is the synthesis of any type of RNA from a DNA template
If a DNA segment has the sequence GCTAA, what will be its complementary RNA sequence?
Which of the following is (are) involved in both transcription and translation?
messenger RNA
A certain bacterial protein is made by a DNA sequence of 120 bases. The mRNA used to make this protein will be at least ______ bases long.
How does RNA differ from DNA?
the sugars in the backbone and one base, uracil
What is meant by the term triplet code with regard to the genetic code?
Three bases code for a single amino acid.
Which of the following is a component of the ribonucleotide?
A strand of DNA has the sequence AATTGG. What would be the complementary sequence on the mRNA strand?
What is the product of transcription?
How does DNA differ from RNA?
DNA has deoxyribose sugar; RNA has ribose sugar.

DNA is a double-stranded molecule; RNA is a single-stranded molecule.

DNA has the bases A, T, C, and G; RNA has the bases A, U, C, and G.

DNA is longer than RNA.
If a cell were stripped of all of its tRNA, which step in protein synthesis would be disrupted?
the attachment of amino acids to build polypeptides
What is a codon?
a three-base sequence of mRNA that codes for a specific amino acid
If one were to disrupt the function of the E site in a ribosome, what would happen to a protein being synthesized?
Two amino acids would be linked, and then synthesis would arrest.
Which of the following carries amino acids to ribosomes, where amino acids are linked into the primary structure of a polypeptide?
What is the function of ribosomes in protein synthesis?
They provide a site for transfer RNAs to link to messenger RNAs.
Which of the following is NOT involved in translation?
Which of the following is a correct statement about mRNA?
A single mRNA molecule may be translated again and again by multiple ribosomes.
Where do mRNA, amino acids, and tRNAs come together to make a protein?
at the ribosomes
Which of the following is a correct statement about translation?
The large ribosomal subunit does not join the translation process until after the first tRNA has arrived.
During the elongation phase of translation, tRNAs, carrying their specific amino acids, are accepted by the _____ of the ribosome.
A site
tRNAs bring appropriate amino acids to the ribosome because they recognize ______ with their respective _____.
codons; anti-codons
tRNA functions to ___________.
translate codons on nucleic acids to amino acids
The ribosome is________.
a complex of RNA and protein with two subunits
How do cells increase the speed of protein translation?
by allowing multiple ribosomes to translate a single mRNA
A strand of mRNA contains the codon AAU. What would be the corresponding sequence for the anti-codon on the tRNA?
The first amino acid of a newly synthesized polypeptide chain during translation is _____.
Of the 64 codons that exist on the genetic code, three of them, UAA, UGA, and UAG, _______.
do not specify a particular amino acid and provide instructions, such as "stop."
When an RNA molecule is first transcribed, it often contains base sequences that must be eliminated before translation can begin. Such sequences are referred to as ______.
The human genome has information that codes for thousands of proteins, but any given cell produces only a fraction of those proteins. How is this possible?
Genes are regulated so that not all genes are expressed in all cells.
It is estimated that the human genome has from 20,000 to 25,000 genes, yet 90,000-odd proteins are synthesized. What is the mechanism?
alternative splicing
If you alter the promoter of a gene, what have you potentially changed about this gene?
the transcription rate of the gene
Micro-RNAs are 20 to 22 bases long, and about 500 have been discovered. What is their function?
They are regulatory.
The portions of the DNA molecule that are transcribed but NOT ultimately translated are known as___________.
Which of the following statements is (are) true about promoters?
They are associated with specific genes.

They are short sequences in DNA.

They are locations in DNA where regulatory proteins gather.

They control transcription.
Which of the following statements about the Hoxc8 gene is (are) true?
The enhancer of Hoxc8 is different in mice and chickens.

Its transcription rate is higher in mice than in chickens.

The enhancer sequence in mice can increase transcription rates.

It regulates development of thoracic structures in vertebrates such as chickens, snakes, and mice.
Which of the following statements about the function of genes is FALSE?
Only red blood cells have hemoglobin genes.
Humans are estimated to have between 20,000 and 25,000 genes, whereas simpler organisms such as the roundworm Caenorhabditis elegans have 19,000 genes. What could be a possible explanation for humans having a disproportionately low number of genes despite their complexity?
Human mRNA undergoes alternative splicing to make more proteins.
How do micro-RNAs help in genetic regulation?
They interact with mRNAs and target them for destruction.
In eukaryotes, what typically happens to a primary transcript?
It will be modified and then translated.
Our genome codes for small RNAs that regulate gene expression known as ______.
A method, common in humans, of producing different proteins from a single gene is________.
alternative splicing
How has the genetic code changed over time from bacteria to humans?
It has not changed.
The human genome can code for 50,000 to 100,000 proteins, but any given cell might produce only 5,000 to 20,000 proteins at a given time. What is the mechanism of this process?
Genes are regulated, so that not all genes are transcribed in all cells.