DNA and cells - MEIOSIS

Question 1

How many daughter cells does meiosis produce?

Answer 1

4

Question 2

Definition of a gene

Answer 2

A length of DNA that codes for a polypeptide

Question 3

Definition of locus

Answer 3

A position of a gene on a chromosome of DNA

Question 4

Definition of an allele

Answer 4

One of the different forms of a particular gene

Question 5

Definition of homologous chromosomes

Answer 5

A pair of chromosomes, one maternal and one paternal that have the same gene loci

Question 6

Definition of a chromosome

Answer 6

Linear structures made of DNA and proteins, containing specific genes

Question 7

Definition of a chromatid

Answer 7

One of the two strands of a chromosome that are joined together by a single centromere

Question 8

Definition of bivalent

Answer 8

Pair of homologous chromosomes, coiled around each other and joined at multiple points

Question 9

Definition of chiasmata

Answer 9

Points where non-sister chromatids of homologous chromosomes are joined

Question 10

What happens in the first meiotic division?

Answer 10

• Homologous chromosomes pair up and their chromatids wrap around each other
• Portions of chromatids may be exchanged (crossing over)

Question 11

What happens in the second meiotic division?

Answer 11

Chromatids move apart

Question 12

What occurs during prophase I?

Answer 12

• Chromosomes condense
• Nuclear membrane breaks down
• Spindle fibres form

Question 13

What occurs during metaphase I?

Answer 13

• Homologous chromosomes line up at the equator and bind to spindle fibres
• Independent segregation
• Crossing over

Question 14

What occurs during anaphase I?

Answer 14

Homologous chromosomes separate - they are pulled by centromeres

Question 15

What occurs during telophase I?

Answer 15

• Spindle fibres break down
• Nuclear envelope reforms
• Chromosomes partially unveil

Question 16

How many cells are produced after cytokinesis of meiosis I?

Answer 16

2 daughter cells

Question 17

What occurs during prophase II?

Answer 17

• Chromosomes condense
• Nuclear membrane breaks down
• Spindle fibres form

Question 18

What occurs during metaphase II?

Answer 18

• Chromosomes line up at equator
  Spindle fibres attach to centromere
• Sister chromatids split at centromere

Question 19

What occurs during anaphase II?

Answer 19

• Spindle fibres contract, pulling sister chromatids towards poles
• Now chromosomes again
• Centromere splits

Question 20

What occurs during telophase II?

Answer 20

• Spindle fibres break down
• Nuclear envelope reforms
• Chromosomes partially uncoil

Question 21

How many cells are produced after cytokinesis of meiosis II?

Answer 21

4 daughter cells
- Haploid number of chromosomes

Question 22

How does meiosis increase genetic variation?

Answer 22

• Independent segregation of homologous chromosomes
• New combinations of maternal and paternal alleles by crossing over (genetic recombination)

Question 23

What is non-disjunction?

Answer 23

• When the chromosomes fail to separate
• Gamete can have two of the same chromosome

Question 24

How does non-disjunction cause problems and can you give an example?

Answer 24

• During formation, the zygote may have 3 of the same chromosome instead of 2
• Eg. Trisomy of chromosome 21 results in Down Syndrome

Question 25

How would you describe homologous chromosomes?

Answer 25

Same genes
Same loci
Different variations of alleles