MEIOSIS L11

Question 1

heredity

Answer 1

• transmission of traits from one generation to the next

Question 2

variation

Answer 2

• differences between individuals

Question 3

genetics

Answer 3

• the study of heredity and hereditary variation

Question 4

gametes

Answer 4

• reproductive cells that transmit genes from one generation to the next

Question 5

advantages of asexual

Answer 5

• fast
• low E required
• safe
• lots of offspring

Question 6

advantages of sexual

Answer 6

• genetic variation
• offspring represent novel combinations of parents genes
• better able to respond to change or stress

Question 7

why meiosis is good

Answer 7

• cell divides twice
• 1 diploid – 4 haploid
• if gametes have same chromosome number as parents, chromosome number doubles when the fuse

Question 8

karyotype

Answer 8

• orderly display of chromosomes

Question 9

life cycles

Answer 9

• sequence of stages from generation to generation

Question 10

what do fertilization and meiosis have in common

Answer 10

• occur in all sexual life cycles
• alternate
• timing varies

Question 11

human life cycle

Answer 11

• meiosis – haploid gametes – fertilization – diploid zygote – mitosis

Question 12

what cells can undergo mitosis

Answer 12

• n

- 2n

Question 13

what cells can undergo meiosis

Answer 13

• 2n

Question 14

meiosis

Answer 14

• reduction division
• 4 stages
• 2 cell divisions
• interphase
• meiosis 1
• interkinesis
• meiosis 2

Question 15

interphase

Answer 15

• like before mitosis
• chromosomes and centrioles duplicate
• each chromosome is now 2 sister chromatids

Question 16

meiosis 1

Answer 16

• prophase 1
• metaphase 1
• anaphase 1
• telophase 1

Question 17

prophase 1

Answer 17

• crossing over
• genes in chromosomes align
• synaptonemal complex forms - protein structure
• results in tetrad: 2 homologous chromosomes (4 chromatids) held together
• chromatin condenses
• centromeres and kinetochores of homologous chromosomes separate
• sister chromatids still attached
• chiasmata form
• nuclear envelope breaks down, spindle forms

Question 18

metaphase 1

Answer 18

• tetrads align at metaphase plate
• homologous chromosomes orient towards opposite poles
• both sister kinetochores of one chromosome – spindle for same pole
• kinetochores of homologous chromosomes – spindle for opposite pole

Question 19

anaphase 1

Answer 19

• sister chromatids still connected
• chromosomes act independently
• direction depends on orientation of tetrad

Question 20

telophase 1

Answer 20

• chromosomes may decondense
• nuclear envelope reforms
• cytokinesis occurs
• results in 2 haploid cells

Question 21

meiosis 1 summary

Answer 21

• start: 1 cell, 2n, duplicated chromosomes
• end: 2 cells, n, duplicated chromosomes
• diploid – haploid
• homologous pairs line up at metaphase plate

Question 22

interkinesis

Answer 22

• time between 1st and 2nd meiotic divisions
• no S phase
• no DNA synthesis

Question 23

meiosis 2

Answer 23

• prophase 2
• metaphase 2
• anaphase 2
• telophase 2
• similar to mitosis
• chromatids separate in daughter cells

Question 24

meiosis 2 summary

Answer 24

• start: 2 cells, n, duplicated chromosomes
• end: 4 cells, n, unduplicated chromosomes
• each daughter cell is genetically unique
• no crossing over
• amount of DNA per cell is reduced
• ploidy does not change