Genetics

Question 1

P and Q arms

Answer 1

the chromosome is divided by the centromere into a short arm, the p-arm, and a long arm, the q-arm

Question 2

Metacentric chromosomes

Answer 2

arms of the same size

Question 3

Sub metacentric chromosomes

Answer 3

centromere off-center

Question 4

Acrocentric chromosomes

Answer 4

very short p-arms and centromeres near one end of the chromosome

Question 5

Telocentric chromosome

Answer 5

can occur in human tumors as a result of chromosome rearrangement (the centromere is located at one end of the chromosome so there is a single arm)

Question 6

What are the 5 phases of prophase 1?

Answer 6

Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis

Question 7

Leptotene

Answer 7

chromosomes begin to condense and appear as thin threads, homologous chromosomes begin to pair

Question 8

Zygotene

Answer 8

the synaptonemal complex forms between the homologous chromosomes (this serves to keep the chromosomes aligned)

Question 9

Pachytene

Answer 9

chromosomes condense further becoming shorter and wider, the double-strand breaks and repaired or mature into cross-over events

Question 10

Diplotene

Answer 10

synaptonemal complex breaks down and the homologous chromosome remain attached to each other at chiasmata (points of cross-over)

Question 11

Diakinesis

Answer 11

chromosomes complete their condensation and nuclear envelope breaks down

Question 12

Polyploidy

Answer 12

occurs when there are multiple copies of the entire genome

Question 13

Triploidy

Answer 13

occurs in less than 1% of conceptions and the embryos are almost always not viable

Question 14

Tetraploid embryos

Answer 14

result from an incomplete first mitotic division of the zygote

Question 15

Aneuploidy

Answer 15

occurs when cells or individuals gain or lose a chromosome (this is a common type of mutation occurring in about 5% of clinically recognized pregnancies and are not viable)

Question 16

What causes aneuplodies?

Answer 16

non-disjunction of a chromosome during meiosis (the failure of chromosomes to separate to opposite poles during meiosis resulting in triosomy or monosomy)

Question 17

Trisomy 21

Answer 17

downs syndrome, extra copy of chromosome 21, facial and hand features, MR, congenital heart disease

Question 18

Klinefelter syndrome

Answer 18

males only, have XXY, phenotypically nml until puberty, hypogonadism- low testerone levels leading to testicular atrophy, sterility, and gynecomastia

Question 19

Turner syndrome

Answer 19

female appearance and is due to a chromosome set of 45X (a single sex chromosome), no ovaries, short, webbed neck, broad chest, widely spaced nipples

Question 20

Angelman syndrome

Answer 20

microdeletion on maternal chromosome 15, MR, can’t talk, long periods of laughter

Question 21

Prader-Willi syndrome

Answer 21

microdeletion of paternal chromosome 15, MR, hypotonia (low muscle tone), obesity, hypogonadism, and cryptochidism (absence of testes)

Question 22

Cri-du-chat syndrome

Answer 22

deletion of part of chromosome 5, microcephaly, MR, congenital heart disease, cry that sounds like a cat

Question 23

Trisomy X

Answer 23

47, XXX, phenotypically normal females, tall, low IQ, learning disabilities