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Flashcards in Inherited variation Deck (27):
1

Evolution is possible via

inherited variation

2

2 types of inherited variation?

gene variation and chromosomal variation

3

2 types of gene variation?

variation due to single genes and poly genes

4

types of inheritance for single genes?

recessive/dominant, codominant (spots), incomplete dominance (combined)

5

what populations can single gene variation result in?

monomorphic and polymorphic populations

6

define: monomorphic population

members show no variation of a particular trait (due to single gene with one allele)

7

define: polymorphic poluation

members show several variants of a particular trait (due to single gene with multiple alleles)

8

is variation for single genes discontinuous or continuous?

discontinous

9

define: continous

variation in a population forming a continuum of phenotypes. Includes heigh, eye colour.

10

define: discontinous

variation in a population consisting of discrete, non-overlapping phenotypes. Include blood type, yellow/green pea seeds

11

is variation for polygenes continous or discontinous?

continuos

12

can polygene expression be affected by environment

yes but still occurs under controlled conditiosn

13

2 types of chromosomal variation

polyploidy and aneuploidy

14

define: polyploidy

when an organism has more than 2 matching sets of chromosomes

15

how are polyploids formed?

ASK LABROOY

16

define: autopolyploidy

additional sets of chromosomes come from the same species.

17

define: allopolyploidy

additional sets of chromosomes come from another species.

18

many alloploids show

hybrid vigour - superior qualities to that of both parents

19

define: aneuploidy

when the chromosome differs by a small number (usually 1-2) from the standard number of chromosomes for the species

20

why does aneuploidy occur?

usually due to non disjunction (also translocation...)

21

describe non disjunction

when a chromosome pair fails to separate during meiosis and both copies of it go to the same gamete. This results in the gametes having 2/0 copies of a particular chromosome.

22

define: monosomy

 Normal gamete + gamete with 0 copies of a chromosome

23

why is monosomy usually lethal

due to loss of key genes; though polyploids can tolerate loss of 1-2 members of a chromosome set, due to presence of other chromosomes.

24

example of monosomy

Turners’ syndrome 45, X0: affects females, causes sterility due to lack of uterus, abnormal breast development

25

define: trisomy

 Normal gamete + gamete with 2 copies of a chromosome

26

why is trisomy usually lethal

causing miscarriage or severe physical/mental abnormalities leading to early death. Trisomy-21 is the only exception.

27

example of trisomy

47, XY+21 (Down’s syndrome) – characteristic facial features, mild-moderate intellectual disability.