Lecture 16 Flashcards
1
Q
What is disjunction?
A
The pulling apart of homologous chromosomes or sister chromatids in anaphase I and II
2
Q
What is meiotic disjunction?
A
- failure of chromosomes to separate properly
- in meiosis I, homologous chromosomes don’t separate
- in meiosis II, sister chromatids don’t separate
- can occur in mitosis
- results in wrong number of chromosomes
3
Q
What is aneuploidy?
A
- meiotic non-disjunction occurs
- these gametes fuse with normal gamete to form zygote
- zygote has abnormal number of chromosomes
4
Q
What does it mean if a chromosome in monosomic?
A
Missing one chromosome
5
Q
What does it mean if a chromosome is trisomic?
A
Extra chromosome
6
Q
What are the genetic characteristics of down syndrome?
A
- extra chromosome (47)
- on 21st chromosome
- autosomal
7
Q
What is Klinefelter syndrome?
A
- male with extra x chromosome
- 47 chromosomes
- intersex, low testosterone
8
Q
What is turner syndrome?
A
- female missing x chromosome
- 45 chromosomes
- impact depends on who x chromosome is inherited from
9
Q
What is polyploidy?
A
- more than 2 complete chromosome sets
- may be from non-disjunction of all chromosomes or failure of diploid to divide after replication in G2 interphase
- many phenotypically normal
- common in plants
10
Q
What is a chromosomal deletion?
A
- part breaks off and becomes missing
- happens during crossing over
- creates deletion loop
- severe effects
11
Q
What is a chromosomal duplication?
A
- part of chromosome is present more than once
- may happen when broken fragment reattaches to as extra segment to a sister or non-sister chromatid
- harmful effects
12
Q
What is a chromosomal inversion?
A
- part of chromosome is inverted
- breaks at 2 points and inserts as an inverted segment
- changes order of genes
- can lead to infertility as homologous chromosomes cannot line up properly for meiosis
13
Q
What is a chromosomal translocation?
A
- segment of a chromosome attaches to a non-homologous chromosome
- don’t change number of genes, but can change gene expression
14
Q
How does familial down syndrome occur?
A
- parent is carrier of translocation
- results in some gametes missing on of chromosome 1
