Unit 4 Genetics: Large Scale Chromosome Variation

Variationationationation

changes in chromosome type and changes in chromosome number 

What are the two main types of chromosomal changes 

aneuploidy and euploidy (polyploidy)

what are the two kinds of changes in chromosome number

variation in 1 or few individual chromosomes; monosomic or trisomic

what is aneuploidy

variation in the number of complete sets or multiple sets of chromosomes; monoploid or polyploid

what is euploidy (polyploidy)

when an individual only has 1 chromosome set in cases where individuals are typically diploid 

what is monoploidy 

male bees, wasps, and ants develop through parthenogenesis when and unfertilized egg develops into an embryo without fertilization

what is an example of monoploidy

the condition of having multiple sets of chromosomes, most common in plants (grasses especially)

what is polyploidy

Autopolyploids and Allopolyploids 

what are the two types of polyploids

polyploids that are created by chromosome duplication within the same species

what is autopolyploid

odd numbers, triploids (5n, 7n, 9n etc)

which autopolyploids are typically sterile

trivalent or a bivalent and univalent, which always leaves 1 pair alone which can lead to issues with crossing over

what are the two pairing mechanisms for triploids

Spontaneously or induced by colchicine

what are the two ways chromosome doubling can occur 

a toxic plant product of autumn crocus that is used to treat gout and induce chromosome doubling by destabilizing spindle fibers

what is colchicine

two bivalents, one quadrivalent, or trivalent and univalent (sterile)

what are the 3 pairing options for even number autopolyploids

polyploids derived from hybrids of different closely related species 

what are allopolyploids 

fertile

Allopolyploids are often ___ because genomes segregate independently

when chromosome sets are partly homologous allowing them to pair and cross over

what is homeologous

an allopolyploid organism that has a full diploid set of chromosomes from each of its parent species resulting from chromosome doubling which allows it to be fertile and the chromosomes to align properly 

what is a amphidiploid

Poaceae

what family is wheat in

grasses, masses

____ feed the ____

allohexaploid, three genomes A, B, and D with 7 chromosomes each

what is so special about wheat 

fertile crescent (middle East)

where did wheat originate

A and B hybridized then the AB games combined with a D and created ABD which became an amphidiploid AABBDD

in what order were wheats genomes combined

larger seeds, fruits, and vegetative structures (also larger stomas)

what are the benefits of polyploidy in plants

wheat, bananas, strawberries, blueberries, cotton, roses, mums, tulips

what are some common polyploids

nondisjunction during either stage of meiosis

what a causes aneuploidy

Underrepresented (in notes not really sure what it means)

what is a hypoploid

overrepresented (in notes not really sure what it means)

what is a hyperploid

nullisomy, missing a whole pair of chromosomes, monosomy, missing one chromosome, trisomy, one extra chromosome

what are the three types of aneuploidy and what do they mean

21 Down, 13 Patau, 18 Edwards

what are some examples of trisomy

X turners 

what are some examples of monosomys 

1/6 A, 2/6 a, 2/6 Aa, and 1/6 aa

what is the gametic ratio for a Aaa trisomic individual

how adding a whole complete set of chromosomes does not unbalance the genome but removing or adding 1 chromosome throws things off

what is gene dosage referring to

the idea that a normal phenotype requires a 1:1 relative proportion of genes in the genome

what is gene balance

A change in phenotype cause by an abnormal number of wile type alleles (observed in chromosomal mutations)

what is the gene dosage effect

because of gene imbalance, aneuploidy is almost always impactful because the ratio of genes is changed which interferes with normal gene function

what is the key takeaway from gene dosage

Deletions, Duplications, Inversions, and Translocations

what are the 4 types of rearrangements

part of the chromosome is missing; heat, radiation, viruses, chemicals

what is a deletion and what can cause it 

interstitial/intercalary and terminal

what are the two types of chromosomal deletions

some of the internal contents of the chromosome are missing 

what are interstitial or intercalary deletions 

parts of the tips of the chromosomes are missing

what are terminal deletions

cri du chat - missing short arm of chromsome 5 and Prader Willi syndrome deletion in chromosome 15

what are two examples of deletions

chromosomal mutation resulting in the doubling of a section of the chromosome

what is a duplication 

tandem, reverse tandem, terminal tandem

what are the three types of duplications

normal; abc → abcbc

what is a tandem duplication

duplicated part is reversed, abc →abccb

what is a reverse tandem duplication 

abc → ababc

what is a terminal tandem duplication (idk how to describe this pattern so its just an example)

barr mutation in fruit flies on X chromosome

what is an example caused by a duplication

segment of the chromosome is excised, flipped, and reinserted

what are inversions

pericentric and paracentric

what are the two types of inversions

inversion that includes the centromere

what is pericentric inversion

inversion that does not include the centromere

what is paracentric inversion 

segments from one chromosome are detached and reattached to a different chromosome

what is translocation

interstitial and reciprocal

what are the two types of translocations

addition within one chromosome and deletion of the other (cut and paste)

what is interstitial translocation 

swapping of segments of nonhomologous chromosomes

what is reciprocal translocation