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Flashcards in Genetics Deck (23):
1

P and Q arms

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

2

Metacentric chromosomes

arms of the same size

3

Sub metacentric chromosomes

centromere off-center

4

Acrocentric chromosomes

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

5

Telocentric chromosome

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)

6

What are the 5 phases of prophase 1?

Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis

7

Leptotene

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

8

Zygotene

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

9

Pachytene

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

10

Diplotene

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

11

Diakinesis

chromosomes complete their condensation and nuclear envelope breaks down

12

Polyploidy

occurs when there are multiple copies of the entire genome

13

Triploidy

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

14

Tetraploid embryos

result from an incomplete first mitotic division of the zygote

15

Aneuploidy

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)

16

What causes aneuplodies?

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

17

Trisomy 21

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

18

Klinefelter syndrome

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

19

Turner syndrome

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

20

Angelman syndrome

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

21

Prader-Willi syndrome

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

22

Cri-du-chat syndrome

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

23

Trisomy X

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