Lecture Exam 4

Question 1

Which of the following best describes the pattern of inheritance for mitochondrial DNA?

Answer 1

It is usually inherited entirely from the mother

Question 1

Which of the following can directly cause genetic disease? Check all that apply.

Answer 1

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

Question 2

During meiosis, the process of ___ produces gametes, and therefore offspring, that have extra or missing chromosomes.

Answer 2

nondisjunction

Question 3

Gaining one extra autosome, in addition to the typical diploid number is called

Answer 3

trisomic

Question 3

Having one or more extra or missing chromosomes is called

Answer 3

aneuploidy

Question 4

The loss of a single autosome is called

Answer 4

monosomic

Question 5

The affects associated with three copies of chromosome 21 are referred to as

Answer 5

Down syndrome

Question 6

The affects associated with a single X chromosome and no Y chromosome are referred to as

Answer 6

Turner syndrome

Question 7

The affects associated with two X chromosomes and one Y chromosome are referred to as

Answer 7

Kleinfelter syndrome

Question 8

Female gametes with no sex chromosomes are produced when the two X chromosomes fail to ___ during meiosis

Answer 8

separate

Question 9

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?

Answer 9

50

Question 10

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

Answer 10

Females are XX, males are XY and wing scales are caused by a dominant allele on the X chromosome.

Question 11

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?

Answer 11

25

Question 12

A crossover in meiosis is an exchange of genetic material between

Answer 12

non-sister chromatids of homologous chromosomes.

Question 13

A Barr body is typically found in the nucleus of

Answer 13

female somatic cells only.

Question 14

Random orientation of homologous chromosomes occurs in _________ of meiosis

Answer 14

metaphase I

Question 15

Of the 23 pairs of human chromosomes, 22 pairs are homologous and are found in both males and females. These are called _________

Answer 15

autosomes

Question 16

Traits that are controlled by genes located on the X chromosome are said to be _________

Answer 16

sex-linked

Question 17

Allele pairs are most likely to assort independently of one another when

Answer 17

they are on different chromosomes.

Question 18

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

Answer 18

crossing over.

Question 19

Occasionally, chromosomes fail to separate during meiosis, leading to daughter cells that have an atypical number of chromosomes. This phenomenon is called

Answer 19

nondisjunction.

Question 20

The loss one copy of an autosome is called

Answer 20

monosomic

Question 21

In humans, individuals with trisomy of the _________ chromosome are most likely to survive until adulthood.

Answer 21

21st

Question 22

Hemophilia is caused by a

Answer 22

recessive allele on the X chromosome.

Question 22

A human female with only one X chromosome is said to have a condition called

Answer 22

Turner syndrome.

Question 23

Amniocentesis is a procedure that is normally used

Answer 23

for diagnosis of genetic disorders.

Question 24

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?

Answer 24

In humans, the male determines the gender of the offspring, and in birds the female determines the gender.

Question 25

In humans, if nondisjunction led to an individual with a genotype of XXY, that person would

Answer 25

be male because each cell has one Y chromosome.

Question 26

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?

Answer 26

Heterozygous individuals have an advantage over individuals with two normal alleles.

Question 27

The most common fatal genetic disorder of caucasians is

Answer 27

cystic fibrosis.

Question 28

In humans, if nondisjunction led to an individual with a genotype of XO, that person would

Answer 28

be female because each cell lacks a Y chromosome.

Question 29

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?

Answer 29

3:1

Question 30

During bacterial transformation, one or more traits of a cell are altered due to the uptake of DNA from the surrounding environment.

Answer 30

True

Question 31

Avery, MacLeod, and McCarty were the first scientists to describe the process of bacterial transformation.

Answer 31

False

Question 32

Griffith determined that DNA is the substance responsible for bacterial transformation.

Answer 32

False

Question 33

During Griffith's experiments, a nonvirulent form of S. pneumoniae was transformed into a virulent form.

Answer 33

True

Question 33

During their experiments, Avery, MacLeod, and McCarty discovered that the removal of nearly all protein from their preparation destroyed its transforming activity.

Answer 33

False

Question 34

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?

Answer 34

Complementarity of the bases

Question 35

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)

Answer 35

22

Question 36

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.

Answer 36

complementaryCorrect

Question 37

DNA consists of two antiparallel strands of nucleotides held together by

Answer 37

hydrogen bonds.

Question 38

creates a short RNA primer that is complementary to a DNA template.

Answer 38

DNA primase

Question 39

Chargaff's rules for the pairing of nitrogen bases is

Answer 39

A = T and G = C.

Question 40

Information obtained by Franklin from X-ray crystallography on DNA suggested that it is shaped like a

Answer 40

helix

Question 41

The site where the two original DNA strands separate and active replication occurs is called the

Answer 41

replication fork.

Question 42

During DNA replication, DNA pol III synthesizes the lagging strand in segments, called

Answer 42

Okazaki fragments.

Question 43

During replication, which enzyme unwinds the DNA double helix?

Answer 43

DNA helicase

Question 44

If we think of the DNA double helix as a twisted ladder, what makes up the rungs or steps of the ladder?

Answer 44

Purines and pyrimidines

Question 45

Viruses that attack bacteria are called

Answer 45

phages

Question 46

Which enzyme adds new nucleotides to the end of a growing strand?

Answer 46

Polymerase

Question 47

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

Answer 47

transformed

Question 48

Nucleotides have a phosphate group attached at the _________blank carbon atom of the sugar.

Answer 48

5'

Question 49

The lagging strand is replicated with a series of Okazaki fragments and that is why its synthesis is considered to be

Answer 49

discontinuous.

Question 50

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?

Answer 50

Watson and Crick

Question 51

Who demonstrated that phage genetic material is DNA and not protein?

Answer 51

Hershey and Chase

Question 52

If a mutation produced helicase that was unable to hydrolyze ATP, DNA replication would be

Answer 52

stopped

Question 53

The correct structure of DNA monomers can be presented as

Answer 53

phosphate–sugar–base.

Question 54

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

Answer 54

Helicase Single strand binding proteins primase dna polymerase I

Question 55

DNA affects the traits of an organism by providing the instructions for synthesizing _________blank.

Answer 55

proteins

Question 56

Gene expression involves two phases, _________blank and translation.

Answer 56

transcription

Question 57

Messenger RNA molecules contain information that is used to synthesize _________blank.

Answer 57

polypeptides

Question 58

To begin transcription, RNA polymerase must bind to a segment of DNA called the _________blank.

Answer 58

promoter

Question 59

The strand of DNA that is not transcribed is called the _________blank strand.

Answer 59

coding

Question 60

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.

Answer 60

codonsCorrect

Question 61

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.

Answer 61

splicingCorrect

Question 62

The polypeptide-making organelles, which consist of protein combined with RNA, are called

Answer 62

ribosomes

Question 63

Which base in an anticodon will pair with the base adenine in a codon?

Answer 63

UracilCorrect

Question 64

The A, P, and E sites are progressively occupied by amino acids being assembled into a polypeptide. These sites are part of

Answer 64

the large ribosomal subunit.

Question 65

In eukaryotic cells, transcription occurs

Answer 65

inside the nucleus.

Question 66

How many unique mRNA codons can be constructed from the four different RNA nucleotides?

Answer 66

64Correct

Question 67

Eukaryotic mRNA molecules may contain noncoding sequences that must be removed before translation. These are called

Answer 67

introns

Question 68

In eukaryotes, pre-mRNA processing may involve all of the following except

Answer 68

removal of exons from the pre-mRNA.

Question 69

The Central Dogma of biology can be stated as

Answer 69

DNA→ RNA→ Proteins.

Question 70

What is the first step during transcription initiation in prokaryotes?

Answer 70

RNA polymerase binds to the promoter

Question 71

RNA polymerase binds to a region of the DNA called the

Answer 71

promoter

Question 72

begins to unwind and separate the 2 strands of the DNA double helix.

Answer 72

RNA polymerase

Question 73

Actual synthesis of the RNA transcript begins at the

Answer 73

start site

Question 74

Successive RNA nucleotides are added to the 3' end of the growing RNA chain during a process called

Answer 74

elongation

Question 75

When RNA polymerase reaches a ___, the RNA transcript and RNA polymerase separate from the DNA, and the DNA within the transcription bubble rewinds.

Answer 75

terminator sequence

Question 76

The principle of colinearity of genes and proteins does not apply to eukaryotes because

Answer 76

most eukaryotic genes contain introns.