Lecture 11

Question 1

How do allopolyploids arise?

Answer 1

Hybridisation of two closely related species with chromosome doubling

Question 2

How can allopolyploidy be useful in agriculture?

Answer 2

Can be used to rapidly develop new types of crops

Question 3

How can aneuploidy arise?

Answer 3

A chromosome can be lost in mitosis or meiosis if its centromere is deleted
Small chromosomes produced through translocations are often lost
Aneuploid gametes arise through non-disjunction in meiosis and mitosis

Question 4

What is nullisomy?

Answer 4

Loss of both homologous pairs

Question 5

What is tetrasomy?

Answer 5

gain of two homologous chromosomes

Question 6

What is the most common cause of aneuploidy?

Answer 6

Non-disjunction, which can occur at meiosis or mitosis but is more common in meiosis, specifcally meisosis I
Non-disjunction increases if there is no crossing over as this is necessary for normal chromosome pairing

Question 7

What are the effects of aneuploidy?

Answer 7

Dramatic alterations of phenotype as the dosage of some genes is altered, causing a corresponding change in relative concentrations of gene products
therefore aneuploid mutations are frequently lethal in both pants and animals, with the exception of the the mammalian sex chromosomes

Question 8

What is kllinefelter syndrome?

Answer 8

A condition where the individual is XXY

Question 9

What is the theory behind the increased incidence of downs syndrome with increased maternal age?

Answer 9

Female mammals are born with primary oocytes which are suspended in the diplotene substage of prophase I of meiosis, components of the spindle may break down over time leading to more regular nondisjunction events at later ages