Chromosome Changes (Lec 11)

Question 1

Findings suggest that Down Syndrome is not due to a single gene but is caused by complex interactions among multiple genes that are affected when an extra copy of which chromosome is present?

Answer 1

21

Question 2

Duplications, deletions, inversions, and translocations are all type of what?

Answer 2

chromosome rearrangements

Question 3

True or False?

In a chromosome inversion, a segment of the chromosome is turned 180 degrees

Answer 3

true

Question 4

Type of duplication in which the duplicated region is immediately adjacent to the original segment. Ex. AB*CDEFGefg

Answer 4

tandem duplication

Question 5

Type of duplication in which the duplicated region is located some distance from the original segment, either on the same chromosome or on a different one. EX. AB*CDEFGab

Answer 5

displaced duplication

Question 6

A duplication in which the duplicated region is inverted. Ex. ABba*CDEFG

Answer 6

reverse duplication

Question 7

What causes unequal crossing over of wild type chromosomes and what is the result?

Answer 7

chromosomes that do not align properly; results in one chromosome containing a duplication and the other chromosome containing a deletion

Question 8

What is the result of unequal crossing over between bar chromosomes (each have two copies of Bar)?

Answer 8

a chromosome with three Bar copies and a wild type chromosome

Question 9

In regards to chromosome rearrangement, why can a large deletion be easily detected?

Answer 9

the chromosome is noticeably shortened and the normal chromosome must loop out during the pair of homologs

Question 10

In regards to chromosomal rearrangements, what are the effects of deletions?

Answer 10

imbalances in gene product, expression of a normally recessive gene, haploinsufficency

Question 11

This type of deletion is a series of X-linked wing mutations in drosophila that can act as a recessive lethal

Answer 11

Notch

Question 12

In what phase of meiosis does the normal chromosome loop out in order to allow for correct pairing and alignment between chromosomes?

Answer 12

prophase I

Question 13

What does Notch code for?

Answer 13

a receptor that transmits signals received from outside the cell to the cell’s interior

Question 14

Loss of all copies of Notch gene prevents normal development, acting as what?

Answer 14

a recessive lethal

Question 15

In regards to chromosome rearrangement, specifically inversion, what is the type of inversion that does not include the centromere?

Answer 15

Paracentric inversion

Question 16

In regards to chromosome rearrangement, specifically inversion, what is the type of inversion that includes the centromere?

Answer 16

Pericentric inversion

note: “i” in pericentric is for “includes” centromere

Question 17

ABCDEFG to ABCFEDG is an example of what type of chromosome rearrangement?

Answer 17

Paracentric inversion

Question 18

ABCDEFG to ADCBEFG is an example of what type of chromosome rearrangement?

Answer 18

Pericentric inversion

Question 19

ABCDEFG to ABCDEFGEFG is an example of what type of chromosome rearrangement?

Answer 19

Tandem duplication

Question 20

ABCDEFG to ABCDEFGAB is an example of what type of chromosome rearrangement?

Answer 20

Displaced duplication

Question 21

ABCDEFG to ABBACDEFG is an example of what type of chromosome rearrangement?

Answer 21

Reverse duplication

Question 22

How is translocation different from crossing over?

Answer 22

Crossing over is the exchange of genetic material between homologous chromosomes while translocation involves the transfer or movement of genetic material between non-homologous chromosomes.

Question 23

In regards to a pairing of a WT chromosome with a chromosome containing paracentric inversion in a heterozygous individual, formation of an inversion loop and thus crossing over with inversion results in an unusual structure. Describe the chromatids of this structure after this occurs

Answer 23

One of the four chromatids has two centromeres, one lacks a centromere

Question 24

In regards to a pairing of a WT chromosome with a chromosome containing paracentric inversion in a heterozygous individual, in anaphase I, the centromeres separate, stretching the dicentric chromatid which breaks. What happens to the chromosome lacking a centromere?

Answer 24

it is lost

Question 25

In regards to a pairing of a WT chromosome with a chromosome containing paracentric inversion in a heterozygous individual , what are the resulting gametes like after anaphase II?

Answer 25

two gametes contain nonrecombinant chromosomes: one WT and one with inversion; the other two chromosomes contain recombinant chromosomes that are missing some genes

Question 26

True or False? | The resulting recombinant gametes from inversion in a heterozygous individual are still viable.

Answer 26

false; they are nonviable due to missing genes

Question 27

In regards a pairing of a WT chromosome with a chromosome containing pericentric inversion in a heterozygous individual, describe the unusual structure that is formed, specifically the chromatids.

Answer 27

two of the resulting chromatids have too many copies of some genes and no copies of others

Question 28

In regards to inversions in meiosis, do homozygous individuals have problems during meiosis?

Answer 28

no, only heterozygous individuals

Question 29

Heterozygous individuals demonstrate reduced recombination in ____ inversion, as gametes formed result in nonviable offspring and have abnormal gametes formed in ___ inversion.

Answer 29

paracentric; pericentric

Question 30

_____ entails the movement of genetic material between non-homologous chromosomes

Answer 30

translocation

Question 31

This type of translocation is more common and involves the movement of material between non homologous chromosomes

Answer 31

reciprocal translocation

Question 32

This type of translocation involves the movement of genetic material from one chromosome to another without any reciprocal exchange

Answer 32

non-reciprocal translocation

Question 33

Robertsonian translocation results in what?

Answer 33

a large metacentric chromosome and a fragment that often fails to segregate and is lost

Question 34

In prophase I when alignment of chromosomes occurs, what kind of structure is formed for translocation

Answer 34

a crosslike configuration that allows homologous sections from one chromosome to match to two other chromosomes

Question 35

In regards to translocation segregation patterns, in anaphase I, the chromosomes separate in how many different ways?

Answer 35

one of three different ways: alternate segregation adjacent-1 segregation adjacent-2 segregation (rare)

Question 36

Out of the three types of translocation segregation, which type produces viable gametes after anaphase II?

Answer 36

only alternate segregation; gametes resulting from adjacent-1 and adjacent-2 segregation are nonviable because some genes are present in two copies, whereas others are missing

Question 37

Fragile-X syndrome is named after a fragile site on the human X chromosome. What are some characteristics of the syndrome?

Answer 37

mental retardation; x-linked inheritance; 1 in 1250 male births; results from an increase in the number of repeats of a CGG trinucleotide

Question 38

What does G banding reveal?

Answer 38

bands rich in A-T base pairs

Question 39

What does Q banding reveal?

Answer 39

difference in relative amounts of C-G and A-T base pairs

Question 40

What does C banding reveal?

Answer 40

regions with centromeric heterochromatin

Question 41

What does R banding reveal?

Answer 41

bands rich in C-G base pairs

Question 42

What is the genetic basis of Cri-du-chat syndrome and what is the phenotype?

Answer 42

deletion on short arm of chromosome 5; infants often have a high-pitched cry, also characterized by intellectual disability and delayed development, small head size, low birth weight and weak muscle tone. Some children are born with a heart defect

Question 43

What is the genetic basis of Wolf-Hirschhorn syndromee and what is the phenotype?

Answer 43

chromosome deletion on short arm of chromosome 4; distinct craniofacial phenotype, growth and mental retardation, seizures, heart defects

Question 44

What is the genetic basis of Williams-Beuren syndrome and what is the phenotype?

Answer 44

deletion on short arm of chromosome 7; facial features, heart defects, mental impairment

Question 45

What is the genetic basis of Prader-Wili syndrome and what is the phenotype?

Answer 45

deletion on short arm of chromosome 15; feeding difficulty at early age, but becoming obese after 1 year