2.2 - cell division

Question 1

what is interphase

Answer 1

• longest stage of eukaryotic cell cycle
• cells grow + synthesise new organelles, proteins, + DAN in prep for mitosis

Question 2

what is mitosis

Answer 2

• form of cell division
• produces two genetically identical diploid daughter cells

Question 3

why is mitosis important

Answer 3

important for growth of tissue + repair and replacement of cells

Question 4

name the stages of mitosis

Answer 4

• prophase
• metaphase
• anaphase
• telophase

Question 5

summarise process of mitosis

Answer 5

prophase - nuclear envelope breaks down, chromosomes condense, centrioles move to opposite poles of cell
metaphase - sister chromosomes line up at equator, centromeres attach to spindle fibres
anaphase - sister chromatids separated + pulled apart to opposite poles
telophase - nuclear envelope reforms, spindle fibres break down, chromosomes uncoil

Question 6

what are sister chromatids

Answer 6

pair of identical chromatids formed by DNA replication, joined by centromere

Question 7

what is cytokinesis

Answer 7

division of cytoplasm at end of mitosis to produce 2 new daughter cells

Question 8

mitosis in plant cells

Answer 8

• occurs in meristematic cells only
• cell doesn’t change shape
• no centrioles involved
• no micro filaments involved
• some spindle fibres remain during cytokinesis

Question 9

mitosis in animal cell

Answer 9

• occurs in most tissues
• before mitosis, cell becomes rounded
• involves centrioles
• involves microfilaments
• spindle fibres disappear prior to cytokinesis

Question 10

what may unrestricted mitosis lead to

Answer 10

cancerous growths

Question 11

what is meiosis

Answer 11

• form of cell division
• produces 4 genetically different daughter cells (gametes) w/ haploid number of chromosomes
• involves 2 divisions

Question 12

significance of meiosis in reproduction

Answer 12

• gametes must be haploid so when combining in fertilisation, the full number of chromosomes is present within resulting zygote
• creates genetic variation

Question 13

what is meiosis I

Answer 13

• first stage of meiosis
• homologous chromosomes separated to from 2 haploid cells

Question 14

describe what happens in meiosis I

Answer 14

1. homologous chromosomes pair to form bivalents
2. crossing over occurs at chiasmata
3. cell divides in 2; independent segregation of homologous chromosomes, each cell contains either maternal or paternal copy

Question 15

what are homologous chromosomes

Answer 15

• pair of chromosomes w/ genes at same locus
• one maternal + one paternal
• some alleles may be same while others are different

Question 16

define crossing over

Answer 16

• process in meiosis I
• homologous chromosomes pair up, their chromatids wrap around one another + their alleles are exchanges at equivalent portions of chromatids
• creates genetic variation

Question 17

what is independent segregation

Answer 17

random separation of homologous chromosomes in meiosis I that produces genetic variation

Question 18

what is meiosis II

Answer 18

• second stage of meiosis
• sister chromatids separated to form 4 haploid gametes

Question 19

describe what happens in meiosis II

Answer 19

1. independent segregation of sister chromatids
2. each cell divides again, producing 4 haploid cells

Question 20

how does meiosis produce genetic variation

Answer 20

• crossing over during meiosis I
• independent assortment of homologous chromosomes + sister chromatids
• results in new combos of alleles