Exam 2

Question 1

What are the three component parts of a nucleotide?

Answer 1

Sugar, phosphate, and a base.

Question 2

Which parts make up the structural ‘sides of a ladder’ part of a DNA molecule?

Answer 2

Sugar and phosphate.

Question 3

What is the relationship among DNA, a gene, and a chromosome?

Answer 3

A chromosome contains hundreds of genes which are composed of DNA.

Question 4

Name one difference between DNA and RNA.

Answer 4

DNA contains thymine, and RNA contains uracil. DNA contains deoxyribose sugar, and RNA contains ribose sugar. DNA is usually double-stranded, and RNA is usually single-stranded.

Question 5

Define mutation.

Answer 5

A change in the DNA sequence.

Question 6

Why are mutations important?

Answer 6

They provide variation that can result in evolutionary change.

Question 7

How can a gene be mutated with no resulting change in the protein that is produced from that gene?

Answer 7

A codon has changed, but it codes for the same amino acid as the original codon.

Question 8

What is a Barr body?

Answer 8

An inactivated X chromosome in female mammals.

Question 9

Define genotype.

Answer 9

The combination of alleles carried by an individual.

Question 10

Define phenotype.

Answer 10

The physical expression of the genotype.

Question 11

Define heterozygote.

Answer 11

An individual whose two alleles for a gene are different forms.

Question 12

Define incomplete dominance.

Answer 12

Heterozygotes show an intermediate phenotype.

Question 13

Define genetic codominance.

Answer 13

The phenotype of the heterozygote expresses the traits of both alleles present.

Question 14

What is the result of nondisjunction during meiosis?

Answer 14

Abnormal chromosome numbers.

Question 15

What are the possible genotypes for an individual who is square and has green toes, given R = round, r = square, G = green toes, and g = pink toes?

Answer 15

rrGG or rrGg

Question 16

During which specific stage of the cell cycle are the chromosomes replicated?

Answer 16

S phase of interphase.

Question 17

In what phase of meiosis does synapsis of homologous pairs occur; crossing over may occur?

Answer 17

Prophase I.

Question 18

In what phase of meiosis are individual chromosomes aligned at the center of the cell?

Answer 18

Metaphase II.

Question 19

In what phase of meiosis do homologous chromosome pairs separate and move away from the middle of the cell?

Answer 19

Anaphase I.

Question 20

A cell with a diploid (2N) chromosome number of 18 undergoes mitosis. How many daughter cells will be produced and how many chromosomes will each daughter cell contain?

Answer 20

2 daughter cells, each with 18 chromosomes.

Question 21

A cell with a diploid (2N) chromosome number of 18 undergoes meiosis. How many daughter cells will be produced, and how many chromosomes will each daughter cell contain?

Answer 21

4 daughter cells, each with 9 chromosomes.

Question 22

What are the names of the steps of protein synthesis?

Answer 22

Transcription and Translation.

Question 23

Where does transcription take place?

Answer 23

Nucleus.

Question 24

Where does translation take place?

Answer 24

Ribosomes in the cytoplasm.

Question 25

What is the role of mRNA?

Answer 25

Carries information from DNA to the ribosomes.

Question 26

What is the role of tRNA?

Answer 26

Brings amino acids to the ribosomes.

Question 27

What is a codon?

Answer 27

An mRNA triplet that codes for a specific amino acid.

Question 28

What is an anticodon?

Answer 28

A set of 3 nucleotides on tRNA that matches codons.

Question 29

What bases are complementary to each other in DNA?

Answer 29

A=T and C=G.

Question 30

What is the product of translation?

Answer 30

A protein.

Question 31

What is the definition of a gene?

Answer 31

An actual piece/segment of a DNA molecule in the cell’s nucleus. Most genes carry information for the synthesis of a single protein.

Question 32

What is the flow of information in gene expression?

Answer 32

DNA -> RNA -> Protein.

Question 33

What is the role of RNA polymerase in transcription?

Answer 33

RNA polymerase finds the promoter, unwinds DNA, and links nucleotides to synthesize a single strand of mRNA using bases complementary to those in the DNA.

Question 34

What is the start codon?

Answer 34

The start codon initiates translation.

Question 35

What occurs during the elongation cycle of translation?

Answer 35

tRNAs deliver amino acids to the ribosome to be attached together.

Question 36

What happens when tRNA reaches a stop codon?

Answer 36

Translation terminates and the pieces disassemble.

Question 37

What is the possible effect of a mutation in a somatic cell?

Answer 37

It can change the protein and thus the phenotype, have no effect (silent mutation).

Question 38

Name three types of mutations.

Answer 38

Insertion, deletion, and translocation mutation.

Question 39

What is the effect of insertion or deletion mutations?

Answer 39

They can change the entire sequence.

Question 40

What is the role of mutations in evolution?

Answer 40

Mutations provide the raw material for evolution.

Question 41

What are homeotic genes?

Answer 41

‘Master genes’.

Question 42

What is the SRY gene?

Answer 42

A ‘master gene’ on the human Y chromosome that controls expression of testis formation.

Question 43

What are proto-oncogenes and tumor suppressor genes?

Answer 43

Genes in which mutations can cause the cell cycle to occur repeatedly and rapidly, potentially leading to cancer.

Question 44

What key feature distinguishes meiosis from mitosis?

Answer 44

Pairing/crossing over of homologous chromosomes.

Question 45

What is the result of meiosis?

Answer 45

Haploid cells with recombinant chromosomes.

Question 46

State Mendel's Law of Segregation.

Answer 46

Allele pairs separate or segregate during gamete formation and randomly unite at fertilization.

Question 47

State Mendel's Law of Independent Assortment.

Answer 47

Allele pairs separate independently during the formation of gametes; therefore, different traits are transmitted to offspring independently of one another.

Question 48

What are linked genes?

Answer 48

Genes on the same chromosome that tend to be inherited together.

Question 49

How is sex determined in humans?

Answer 49

Sex chromosome carried by sperm determines sex.

Question 50

Why will sex-linked traits be expressed in males more often than in females?

Answer 50

Males carry only one copy of genes on the X chromosome.

Question 51

What is incomplete dominance?

Answer 51

Heterozygotes show an intermediate phenotype.

Question 52

Give an example of multiple alleles.

Answer 52

Human A, B, O blood types.

Question 53

What is pleiotropy?

Answer 53

Single genes affect more than one phenotypic trait.

Question 54

What are carriers in the context of single-gene disorders?

Answer 54

Heterozygotes for a recessive condition.

Question 55

How does DNA replication ensure genetic constancy during cell division?

Answer 55

DNA replication is semiconservative.

Question 56

What are the three types of RNA and what are their functions?

Answer 56

Messenger RNA (mRNA) codes for building a protein, ribosomal RNA (rRNA) is part of ribosomes, and transfer RNA (tRNA) brings amino acids to the ribosomes.

Question 57

What is the definition of nondisjunction?

Answer 57

The failure of chromosomes to segregate/separate properly during meiosis.