test 2: lecture 9 - meiosis

Question 1

what advantage does sex provide?

Answer 1

genetic variation (caused by egg and sperm) = variation is survival

Question 2

internal fertilization

Answer 2

• enables egg to meet sperm in dry environment
• independence from water
• more efficient

Question 3

what type of cells can divide by meiosis?

Answer 3

diploid

Question 4

diploid

Answer 4

cell has full set of chromosomes

Question 5

haploid

Answer 5

half a set of chromosomes

Question 6

what is the result of meiosis?

Answer 6

4 daughter cells

Question 7

phases of meosis I

Answer 7

interphase, prophase I, metaphase I, anaphase I, telophase I

Question 8

prophase I

Answer 8

• chromosomes condense and homologous pair up
• centrioles migrate to poles
• nuclear membrane breaks down
• synapsis occurs (trading mum/dad genes)
• tetrads form
• non-sister chromatids cross over exchanging genetic infor (chiasmata)

Question 9

metaphase I

Answer 9

• homologous chromosomes arranged in pairs

- kinetochore microtubules are attached to one chromosome from each tetrad (opposite poles)

Question 10

1st source of variation?

Answer 10

random assortment of alleles along linkage group (3 times in each chromosome)

Question 11

linkage group

Answer 11

sequence of groups along a chromosome

Question 12

2nd source of variation

Answer 12

independent assortment (random assortment of whole linkage groups)

Question 13

anaphase I

Answer 13

• disjunction: spindle guides whole chromosomes to poles
• sister chromatids move to same pole
• non-disjunction causes major illness: down syndrome, turner’s syndrome

Question 14

telophase I

Answer 14

• pairs of homologous chromosomes reach poles
• each pole has haploid set
• cytokinesis occurs
• cleavage furrow forms
• no further replication

Question 15

prophase II

Answer 15

spindle reforms and chromosome move to metaphase II plate

Question 16

metaphase II

Answer 16

chromosomes are lined up along plate

Question 17

anaphase II

Answer 17

• centromeres begin separation of sister chromatids
• sister chromatids become individual chromosomes
• chromosomes move towards opposite poles

Question 18

telophase II

Answer 18

• separation of cytoplasm (cells completely split)
• nuclei reform (spindle fibers break uo)
• 4 daughter cells that have independently assorted

Question 19

3rd source of variation

Answer 19

fertilization - egg/sperm used for offspring is random, all combinations are possible