Quiz 3 (Ch. 8)

Question 1

Chromosomes are classified as ______ when the centromere is very close to the center

Answer 1

Metacentric

Question 2

Chromosomes are classified as ______ when the centromere is slightly off center

Answer 2

Submetacentric

Question 3

Chromosomes are classified as ______ when the centromere is significantly off center but not at the end

Answer 3

Acrocentric

Question 4

Chromosomes are classified as ______ when the centromere is at one end

Answer 4

Telocentric

Question 5

What types of features do cytogeneticists use to make a karyotype? (3 things)

Answer 5

i) Size of the chromosomes
ii) Placement of the centromere
iii) Banding patterns

Question 6

Why can mutations in duplications of genes be advantageous?

Answer 6

Because the mutations will often lead to a more specified function of the gene. This is advantageous because the specified function will be more efficient at performing that function

Question 7

What is the removal of a segment of a chromosome called?

Answer 7

Deletion

Question 8

What is the addition of a segment of chromosome called?

Answer 8

Duplication

Question 9

What is it called when a segment of a chromosome is flipped in the opposite orientation?

Answer 9

Inversion

Question 10

What is it called when a chromosomal segment is swapped between nonhomologous chromosomes?

Answer 10

Translocation

Question 11

Euploidy

Answer 11

The number of sets of chromosomes in an organism

Question 12

In what two ways can changes in chromosome number occur?

Answer 12

i) Changes in the number of sets of chromosomes (euploidy)

ii) Changes in the number of chromosomes within a set (ex: from 2 in a set to 4 in a set)

Question 13

What dye is used in G-banding?

Answer 13

Giemsa

Question 14

How is the banding pattern of a chromosome useful? (3 ways)

Answer 14

i) It distinguishes individual chromosomes from each other
ii) It detects changes in chromosome structure
iii) It reveals evolutionary relationships among the chromosomes of closely related species

Question 15

Simple translocation

Answer 15

• A one-way transfer of genetic material

- A piece of a chromosome is attached to another chromosome

Question 16

Reciprocal translocation

Answer 16

• A two-way transfer of genetic material

- Two different types of chromosomes exchange pieces, producing two abnormal chromosomes with translocations

Question 17

How does a deletion occur?

Answer 17

Occurs when a chromosome breaks and a fragment of it is lost

Question 18

How does a deletion affect the phenotype of an organism?

Answer 18

• Generally detrimental
• The larger the deletion, the more likely the phenotype of the organism will be changed
• If genes which are vital to the function of the organism are lost, it can be lethal

Question 19

How do duplications occur?

Answer 19

• Caused by abnormal events during recombination

- Repetitive sequences can cause misalignment between homologous chromosomes

Question 20

Nonallelic homologous recombination

Answer 20

When a crossover occurs between two misaligned chromosomes

Question 21

Gene family

Answer 21

• Consists of two or more genes that are derived from the same ancestral gene
• Ex: The globin gene encodes all subunits that bind oxygen
• –Has 14 paralogs on 3 different chromosomes

Question 22

In what two situations do inversions cause a phenotypic effect?

Answer 22

i) Break point effect - If the inversion break point occurs in a vital gene
ii) Position effect - A gene is repositioned in a way in which it affects its expression

Question 23

Explain why an individual who is heterozygous for an inversion may be phenotypically unaffected but is more likely to have a child which is affected by this inversion

Answer 23

• The abnormality in offspring is due to crossing over within the inverted segment
• During meiosis I, pairs of sister chromatids synapse with each other
• –For the normal & inversion chromosome to synapse properly, an inversion loop must form
• –If a crossover occurs within the inversion loop, very abnormal chromosomes are produced (chromosomes having two or no