Genetics 1 and 2

Question 1

Describe an acrocentric chromosome

Answer 1

chromo with centromere near telomere

Question 2

What is Rob translocation

Answer 2

Occurs when a piece of a chromosome becomes attached to a nonhomologous chromosome.

The two pieces are exchanged equally

• short arm of one acrocentric chromsomes exchanged with long arm of another- metacentric chromosome
• only between acrocentric chromosomes
• Trivalent formation

Question 3

What is reciprocal translocation?

Answer 3

If two nonhomologous chromosomes synapse and undergo crossing over during meiosis I

when two chromosomes exchange terminal pieces of genetic material

Quadrivalent formation

Question 4

a balanced reciprocal translocation involving 2 different chromosomes can lead to what?

Answer 4

the formation of a quadrivalent.

to main homologous pairing

Question 5

What causes translocation Downs?

Answer 5

Robertsonion translocation of chromosomes 14 and 21 whereby there is fusion of the long arms of chr 14 and chr 21

Question 6

What is an isochromosome?

Answer 6

• chromosome with 2 identical arms (2 p arms, 2 q arms)
• Due to centromere fission
• Always unbalanced genetic material
• Always leads to partial trisomy or partial monosomy

Question 7

What is a ring chromsome?

Answer 7

• When chromosome break in 2 places
• Ends of chromosome arm fuse together to form circular structure
• Deleted genetic material nears ends of chromosome is lost

Question 8

What is genetic mosaicism?

Answer 8

2 or more cell populations with distinct karyotypes or genotypes in one individual

Question 9

What is the karyotype for Mosaic Down Syndrome?

Answer 9

46,N/47 +21

Question 10

Describe a sub-metacentric chromosome

Answer 10

closer to one telemore

Question 11

Describe a metacentric chromosome

Answer 11

centromere in the middle

Question 12

How does aneuploidy occur?

Answer 12

• aneuploid gametes can be generated by meiotic nondisjunction
• nondisjunction during maternal meiosis I is the most common cause of aneuploidy