MCBG - Mitosis And Meiosis

Question 1

True or false - one chromosome can be either one OR two DNA molecules?

Answer 1

True - a replicated chromosome is two DNA molecules rather than the usual one.

Question 2

What are the names given to the arms of chromosomes?

Answer 2

P (short) and Q (long) arms

Question 3

What are telomeres?

Answer 3

Repeated sequences at each end of a chromosome/chromatid.

Question 4

Where is a metacentric centromere placed on the chromosome?

Answer 4

In the middle.

Question 5

True or false - all of a human’s chromosomes have telocentric centromeres.

Answer 5

False - humans have none.

Question 6

Where is an acrocentric centromere placed?

Answer 6

Very close to the top of the centromere.

Question 7

What happens in prophase?

Answer 7

Spindle fibres appear and chromosomes condense

Question 8

Describe prometaphase.

Answer 8

Spindle fibres attach to chromosomes, chromosomes condense further.

Question 9

What happens in metaphase?

Answer 9

Chromosomes align down the equator.

Question 10

What happens in anaphase?

Answer 10

Centromeres divide and sister chromatids move to opposite poles.

Question 11

Describe telophase.

Answer 11

Nuclear membrane reforms, chromosomes decondense, spindle fibres disappear.

Question 12

What occurs in cytokinesis?

Answer 12

Cytoplasm divides

Question 13

True or false - sister chromatids have identical DNA and the same alleles?

Answer 13

True

Question 14

Can homologous chromosomes have different alleles?

Answer 14

Yes, they often do.

Question 15

What does meiosis produce?

Answer 15

Four non-identical cells with half of the chromosome content of the parental cell.

Question 16

By which process are eggs and sperm produced?

Answer 16

Meiosis

Question 17

What makes meiosis I different from meiosis II?

Answer 17

In meiosis I, homologous pairs of chromosomes line up and separate. In meiosis II, chromosomes line up and chromatids separate.

Question 18

What are the consequences of meiosis?

Answer 18

Maintains constant chromosome number from generation to generation, and generates genetic diversity (random assortment of chromosomes and crossing over of genetic material).

Question 19

How long does spermatogenesis take?

Answer 19

Around 60 days.

Question 20

How many spermatids are produced from one spermatocyte?

Answer 20

4

Question 21

How long does oogenesis take?

Answer 21

12-50 years

Question 22

How many mature ova are produced from one primary oocyte?

Answer 22

One, and three polar bodies.

Question 23

What is nondisjunction?

Answer 23

When both copies of the chromosome are pulled to one pole instead of splitting.

Question 24

In what stage of the cell cycle does nondisjunction occur?

Answer 24

Anaphase

Question 25

What is a “metaphase spread”?

Answer 25

A technique where stained metaphase chromosomes are spread over a glass slide for analysis.

Question 26

What does this karyotype show? 46,XX

Answer 26

Female with no genetic conditions

Question 27

What does this karyotype show? 47,XY,+21

Answer 27

Male with trisomy 21 (Downs syndrome)

Question 28

What is aneuploidy?

Answer 28

Having the wrong number of chromosomes

Question 29

What is mosaicism?

Answer 29

Presence of two or more cell lines in an individual, can be throughout the body or tissue limited.