Errors In Meiosis + X-Inactivation

Question 1

Is an abnormal number of a particular chromosome

Answer 1

Aneuploidy

*aneu = abnormal

Question 2

Failure of chromosomes to separate properly during meiosis

Answer 2

Non-disjunction

Question 3

Klinefelter Syndrome commonly occurs in?

Answer 3

Males (because of XXY chromosome)

Question 4

XXY chromosomes; described by symptoms such as breast development/wide hips/small testicular size

Answer 4

Klinefelter syndrome

Question 5

Turner syndrome mostly occurs in? Why?

Answer 5

Females because it lacks another X chromosome

Question 6

Characterises the absence of a chromosome (so only one X chromosome present)

Answer 6

Turner syndrome

Question 7

What are Down Syndrome, Klinefelter and Turner Syndrome?

Answer 7

Aneuploidies *an abnormal number of chromosomes in their sex chromosome

Question 8

Chromosome of four resulting gametes during non disjunction at anaphase 1

Answer 8

(N+1)(N+1)(N-1)(N-1)

*remember normal number of chromosomes = 2

Question 9

Chromosome of four resulting gametes during non disjunction in anaphase 2:

Answer 9

(N+1)(N-1)(N)(N)

Question 10

This is the possession of multiple sets of chromosomes

Answer 10

Polyploidy

Question 11

How is polyploidy corrected?

Answer 11

Through self-fertilisation. That’s why most polyploidy occurs in plants

Question 12

The offspring produced after self-fertilisation.

Answer 12

Autopolyploid / zygote

Question 13

Why are the resulting gametes of polyploidy infertile?

Answer 13

Because there’s not enough chromosomes to line up and divide properly. Meiosis won’t work, thus genes cannot be passed on.

Question 14

This removes a chromosomal segment.

Answer 14

Deletion

Question 15

Reverses a segment within a chromosome

Answer 15

Inversion

Question 16

Repeats a segment

Answer 16

Duplication

Question 17

Moves a segment from one chromosome to a non-homologous (not the same) chromosome

Answer 17

Translocation

Question 18

This is the deletion of the tip of short arm of chromosome 5

Answer 18

Lejeune syndrome

Question 19

When the chromosomal segments of chromosome 9 are swapped with chromosome 22

Answer 19

Philadelphia Translocation

Question 20

When the genes in a cell are active all the time. The cell cycle is going at a constant rate.

Answer 20

Overexpression

Question 21

While it can produce standard gametes, there is also a chance that this can produce gametes with genes coding for Down Syndrome/lethal genes.

Answer 21

Familial Down Syndrome

Question 22

Familial Down syndrome is also known as what?

Answer 22

Robertsonian Translocation (between chromosome 14 & 21)

Question 23

has 47 chromosomes, trisomy 21

Answer 23

Standard Down Syndrome

Question 24

What is mosaic patterning?

Answer 24

The random inactivation of X chromosomes

• which means that in some parts of an organisms body, the X gene will be activated (because it is easily accessible by the machinery that will use it); whereas in some parts, the X gene will be inactivated because they are tucked away where they aren’t as accessible
• it creates a mosaic pattern
• each X chromosome codes for a phenotype