Lecture 11

Question 1

What is nondisjunction?

Answer 1

Chromosomes (homologs or sister chromatids) fail to separate in meiosis or mitosis

Question 2

What are two diseases/ disorders that result from nondisjunction?

Answer 2

Turner syndrome - 45, X
Klinefelter- XXY

Question 3

When does nondisjunction occur?

Answer 3

anaphase of mitosis
meiosis I
Meiosis II

Question 4

What do the chromosomes result in, in anaphase of mitosis of nondisjunction?

Answer 4

2N+1 and 2N-1

Question 5

What happens to the chromosomes in meiosis I of nondisjunction?

Answer 5

tetrads fail to separate
N+1 and N-1

Question 6

What happens in meiosis II in nondisjunction?

Answer 6

sister chromatids fail to separate
two good haploid cells and two bad ones (N+1 and N-1)

Question 7

Nondisjunction in meiosis I results in

Answer 7

2 gametes that are n+1 and 2 gametes that are n-1

Question 8

A human individual with 45 chromosomes has a ….

Answer 8

monosomy

Question 9

what causes nondisjunction?

Answer 9

spindle- assembly checkpoint
female meiosis is more error-prone
age- cohesin degrades during the meiotic arrest in oocytes

Question 10

Why are females in meiosis more error prone?

Answer 10

you keep one egg and it energy expensive

Question 11

Monosomy is

Answer 11

2n-1

Question 12

is monosomy usually tolerated in animals?

Answer 12

no

Question 13

what is haploinsufficiency?

Answer 13

it is a single copy of a gene that is insufficient to provide life-sustaining function for organism

Question 14

is monosomy involved in gene dosage?

Answer 14

yes

Question 15

what is trisomy?

Answer 15

(2n+1 chromosomes)

Question 16

definition of trisomy?

Answer 16

extra chromosomes produce a more viable organism than loss of chromosome (if it is small)

Question 17

are trisomic plants viable?

Answer 17

sometimes

Question 18

trisomic plant examples

Answer 18

datura (weed)
oryza sativa (rice)

Question 19

aberrations in the composition and arrangement of chromosomes include

Answer 19

deletions, duplications, inversions, and translocations

Question 20

what is a deletions?

Answer 20

mission region of a chromosome

Question 21

what is it called when a deletion occurs near one end of the chromosome?

Answer 21

terminal deletion

Question 22

what is it called when a deletion occurs from the interior of a chromosome?

Answer 22

intercalary deletion

Question 23

synapsis occur between normal homolog and …

Answer 23

chromosome with intercalary deletion

Question 24

the unpaired region of a normal homolog must

Answer 24

“buckle out” into deletion or compensation loop for synapsis to occur

Question 25

cri du chat means

Answer 25

cry of the cat

Question 26

what is cri du chat

Answer 26

it is a loss/deletion of small variable part of short arm on chromosomes 5

Question 27

what is segmental deletion?

Answer 27

loss/ deletion of small variable part of short arm on chromosome 5 (46,5p-)

Question 28

is cry of the cat inheritied?

Answer 28

no

Question 29

how does cry of the cat arise?

Answer 29

results from sporadic loss of chromosomal material in gametes

Question 30

what does the severity of cry of the cat depend on?

Answer 30

length of deletion