Exam #2 Questions

The improper assortment of sex chromosomes during gametogenesis can be problematic. A man has a condition where all of his gametes undergo normal meiosis I, but meiosis II experiences non-disjunction. He mates with a woman who produces all normal gametes. What is the probability that the fertilized egg will develop into a child with Klinefelter's syndrome (XXY)? Assume that all gametes and zygotes are viable. 0 1/8 1/4 1/3 1/2

0

Two linked genes, (A) and (B), are separated by 20 cM. A man with genotype Aa Bb mates with a woman who is aa bb. The man's mother was aabb. What is the probability that their first two children will both be ab/ab? 0.1 0.16 0.2 0.4

0.16

Two linked genes, (A) and (B), are separated by 30 cM. A man with genotype A_B_ mates with a woman who is Aa bb. What is the probability that their first child will be Aa bb? The man's mother was aa bb. 0 0.125 0.175 0.25 0.5

0.25

Some individuals can be heterozygous for a particular mutation. This means that one of their chromosomes is normal and the other is mutated in some way. Approximately __________ of the gametes produced by an individual heterozygous for an inversion will be viable (assume no crossing over occurs within the inverted section). all none 1/2 1/4 1/8

1/2

Suppose that some cells are grown in culture in the presence of radioactive nucleotides for many generations so that both strands of every DNA molecule have all radioactive nucleotides. The cells are then harvested and placed in a new medium with nucleotides that are not radioactive so that newly integrated nucleotides are not radioactive. What proportion of dsDNA molecules will contain some radioactivity after two rounds of conservative replication? 0 1/2 1/4 1/8 1/16

1/4

The poor assortment of sex chromosomes during gametogenesis can lead to aberrant fertilization products. A woman has a condition where all of her gametes undergo meiosis I normally, but there is nondisjunction of the sex chromosomes in every meiosis II. She mates with a man who produces all normal gametes. What is the probability that a fertilized egg will develop into a child with Turners syndrome (XO)? Assume that all gametes and zygotes are viable. 0 1/8 1/4 1/3 1/2

1/4

A linear dsDNA molecule that is 30% GC and 500 bp long will have _________ hydrogen bonds. 150 500 1150 1400

1150

Two genes, A and B, are located 26 map units apart. Two fully heterozygous individuals are mated. What proportion of the offspring is expected to be recessive for both traits? 10.2% 13.7% 26% None of these is the correct answer.

13.7%

A linear DNA molecule that is 50% GC and 750 bp long will have _________ phosphodiester bonds per strand 749 750 1498 1500 1875

1498

The human chromosome 21 is about 50 million base pairs long. About how many histones would you expect to find associated with this chromosome when it is packaged as chromatin? 250,000 500,000 2,000,000 2,250,000 2,500,000

2,250,000

You are studying a small eukaryotic gene of 4200 bp in length. How many copies of histone H1 would you find along this region of the chromosome? 21 42 210 420 None of the above.

21

You are doing lab work with a new species of beetle. You have isolated lines that breed true for either blue shells and long antenna, or green shells and short antenna. Crossing these lines yields F1 progeny with blue shells and long antenna. Crossing F1 progeny with beetles that have green shells and short antenna yield the progeny below. Given these progeny, what is the distance between the two loci responsible for shell color and antenna length? Blue shell, long antenna 120 Green shell, short antenna 133 Blue shell, short antenna 37 Green shell, long antenna 43 Total 333 33.3 cM 24.0 cM 49.5 cM 8.0 cM The genes are actually assorting independently.

24.0 cM

How many phosphodiester bonds are present in a 1200bp plasmid? 1198 1200 2398 2400

2400

Heat can disrupt hydrogen bonding between DNA strands. We put DNA in a water bath and increase the temperature gradually. Given the options below for AT and GC content, which fragment would be the second to last to denature/melt? 10% AT and 90% GC 30% AT and 70% GC 50% AT and 50% GC 70% AT and 30% GC 90% AT and 10% GC

30% AT abd 70% GC

Two genes, A and B, are located 30 map units apart. A fully heterozygous cis individual is mated to a tester aa bb. What proportion of the offspring is expected to be dominant for both traits? 0% 17% 35% 68%

35%

A gene is 5000 bp long. If this gene if fully complexed with nucleosomes, how many H3 proteins will you find in this piece of DNA? 10 50 125 250 500

50

Only DNA polymerase I has ____________________ but both DNA polymerase I and DNA polymerase III both have ________________. 5′→ 3′ exonuclease activity; 3′→5′ exonuclease activity 3′→5′ exonuclease activity; 5′→ 3′ exonuclease activity 5′→ 3′ polymerase activity; 3′→5′ polymerase activity 3′→5′ polymerase activity; 5′→ 3′ polymerase activity 5′→ 3′ polymerase activity; 3′→5′ exonuclease activity

5′→ 3′ exonuclease activity; 3′→5′ exonuclease activity

The nuclear genome of a single human cell (i.e., the entire diploid complement) contains about 6.4 billion base pairs of DNA. If synthesis at each replication fork occurs at an average rate of 60 nucleotides per second, all the DNA is replicated in 10 minutes. Assume that replication is initiated simultaneously at all origins. How many origins of replication exist in a human diploid genome? 93333 88888 177777 5333333 None of the above

88888

The chromosome count among the apes is very similar. Chimpanzees, gorillas, and orangutans all have 48 chromosomes, whereas humans have 46. Human chromosome 2 is a large, metacentric chromosome with G-banding patterns that closely match those found on two different acrocentric chromosomes of the apes. What would best explain these findings? Meiotic nondisjunction gave rise to a nullisomic gamete. The fusion of two nullisomic gametes produced the ancestor of the human species with 46 chromosomes instead of 48. A translocation took place in a human ancestor, creating a large metacentric chromosome from the two long arms of the ancestral acrocentric chromosomes. The other small chromosome produced by this translocation was lost. A nonreciprocal translocation and subsequent fusion of the chromosomal fragments created a genome of 46 chromosomes without the loss of any genetic information. Infection by a primate virus created a new chromosome when the viral DNA became a permanent part of the genome. Humans were not affected by this virus, so they did not acquire the extra chromosome. Humans have the correct number of chromosomes. The extra chromosome pair in the other apes is a classic case of tetrasomy as a result of meiotic nondisjunction in the primate ancestor.

A translocation took place in a human ancestor, creating a large metacentric chromosome from the two long arms of the ancestral acrocentric chromosomes. The other small chromosome produced by this translocation was lost.

If a corn plant with 1000 kernels is Ctc and 20% of the kernels experience a transposition event at the AC/Ds system at random times during development, how many kernels will be entirely yellow? likely zero fewer than 20 400 about 800

About 800

Indicate which of the following statements is False. Covalent bonds connect nucleotides in a strand; noncovalent interactions hold strands into a double-stranded structure. Uracil is similar to thymine except that uracil lacks a methyl group on the carbon at position 5 on the carbon-nitrogen ring. Frederick Griffith demonstrated that a transforming chemical from dead bacteria could change the genetic information of living bacteria. All of the above statements are true.

All of the above statements are true.

A normal chromosome in a higher eukaryotic species would be expected to contain all of the following except: One centromere Two telomeres Two copies of H2A per nucleosome Satellite DNA All of these are present in this chromosome

All of these are present in this chromosome

Which of the following is not true of bacterial DNA? Most bacterial genomes consist of a single circular DNA molecule. Bacterial DNA is attached to proteins that help to compact it into the nucleoid. Bacterial DNA is confined to a region in the cell called the nucleosome. Many bacteria contain additional DNA in the form of small circular molecules called plasmids. All statements are true

Bacterial DNA is confined to a region in the cell called the nucleosome.

Which of the following best describes the usefulness of colchicine for studying chromosomal mutations? Colchicine inhibits microtubule polymerization, which stalls cells in metaphase with condensed chromosomes. None of these is the correct answer. Colchicine causes chromosomal breakage, leading to inversions and translocations that can be observed with a microscope. Colchicine aids in the formation of microtubules during mitosis, which promotes anaphase and completion of the cell cycle. Colchicine is an inhibitor of oxidative phosphorylation. Reduced mitochondrial function slows down mitosis and increases the number of metaphase cells.

Colchicine inhibits microtubule polymerization, which stalls cells in metaphase with condensed chromosomes

Which statement about mitochondrial genomes is False? In most animals, the mitochondrial genome consists of a single circular DNA molecule. Plant mitochondrial genomes often include multiple circular DNA molecules. Each mitochondrion typically contains a single copy of the mitochondrial genome. All statements are true.

Each mitochondrion typically contains a single copy of the mitochondrial genome.

Which of the following is not a characteristic of A-form DNA compared to B- or Z-form DNA? All of the below characteristics depict A-form DNA Exists when more water is present All of these are characteristics of A-form DNA. Has 50% purines, 50% pyrimidines Has right-handed helixes

Exists when more water is present

Indicate which of the following statements is TRUE. There are three phosphates between each sugar in a molecule of DNA. A-, B-, and Z-form DNA are all right-handed helixes. Ribose sugars have a methyl on the 2′ carbon. There are three hydrogen bonds between AT pairs. Most organisms contain DNA that is rarely 25% A, 25% T, 25% G, and 25%

Most organisms contain DNA that is rarely 25% A, 25% T, 25% G, and 25%

Below are chromosomes where each letter represent a segment of DNA. Two chromosomes have the following segments, where • represents the centromere: K L M • N O P Q R S T U V • W X Y Z What type of chromosome mutation would result in the following chromosomes: K L M • N O P Q R S T U V • W Z Tandem duplication Pericentric inversion Displaced duplication Reverse Duplication None of the above

None of the above

All RNA polymerases synthesize new RNA by adding nucleotides to the __________________of the growing RNA chain. 2′ OH None of these is the correct answer. 3′ phosphate 5′ phosphate nitrogenous base

None of these is the correct answer.

What is the function of DNA ligase during DNA replication? None of these is the correct answer. Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork Reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding Binds to oriC and causes a short section of DNA to unwind Prevents the formation of secondary structures within single-stranded DNA

None of these is the correct answer.

What is the function of the Gyrase proteins in DNA replication? Connects Okazaki fragments by sealing nicks in the sugar- phosphate backbone Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork Reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding Binds to oriC and causes a short section of DNA to unwind Prevents the formation of secondary structures within single-stranded DNA

Reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding

What isotope would you use if you wanted to track viral proteins in an experiment? C14 N15 O18 S35 None of the above

S35

The centromere, a region of non-coding repetitive sequence in chromosomes, can be located in different places along the chromosome. The centromere is located just off of the middle for which type of chromosome? Acrocentric Metacentric Paracentric Submetacentric Telocentric

Submetacentric

Below are chromosomes where each letter represent a segment of DNA. Two chromosomes have the following segments, where • represents the centromere: K L M • N O P Q R S T U V • W X Y Z What type of chromosome mutation would result in the following chromosomes: K L M • N O P O P Q R S T U V • W X Y Z Deletion Displaced duplication Tandem duplication Pericentric inversion Paracentric inversion

Tandem duplication

Which of the following is TRUE regarding nucleosome formation during DNA replication? Nucleosomes are only reassembled on the lagging strand. Nucleosome assembly consists of old histones or newly synthesized histones but not both. Nucleosome assembly occurs at a faster rate in prokaryotes than in eukaryotes. The addition of newly synthesized histones is a part of nucleosome assembly. None of the above are true

The addition of newly synthesized histones is a part of nucleosome assembly.

An individual of AB/ab genotype is testcrossed with an ab/ab and four classes of testcross progeny are found. Two of the classes are MUCH more common than the other two. Which of the following statements is TRUE? The genes A and B are on the same chromosome and very far apart. The genes A and B are probably between 20 and 30 map units apart on the same chromosome. The genes A and B are likely located on different chromosomes. All of the statements are false The genes A and B are likely located very close together on the same chromosome.

The genes A and B are likely located very close together on the same chromosome.

What is the function of helicase in DNA replication? Connects Okazaki fragments by sealing nicks in the sugar- phosphate backbone Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork Reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding Binds to oriC and causes a short section of DNA to unwind None of the above

Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork

What kind of gene would NOT be found in a chloroplast genome? a tRNA gene a gene for a subunit of the electron transport system. a gene for ribosomal protein a gene for a histone protein

a gene for a histone protein