12-Cell Devision

Question 1

cell continuity

Answer 1

all cells develop from pre-existing cells

Question 2

chromosome

Answer 2

coiled threads of DNA and protein that become visible in the nucleus at cell division

Question 3

gene

Answer 3

section of DNA that contains the instructions for the formation of protein

Question 4

haploid cell

Answer 4

one set of chromosomes

Question 5

diploid cells

Answer 5

two sets of chromosomes

Question 6

homologous pair

Answer 6

two chromosomes of similar size with same sequence of genes

Question 7

cell cycle

Answer 7

changes that take place in a cell during the period between one cell division and the next

Question 8

interphase

Answer 8

cell not dividing
chromosomes appear as chromatin
cell very active-produces new organelles and forms chemicals

Question 9

mitosis

Answer 9

a form of nuclear division in which one nucleus divides to form two nuclei,each containing the same number of chromosomes with identical genes

Question 10

Prophase

Answer 10

chromosomes contract-become visible in nucleus as short,thickened strands
fibres begin to appear in the cytoplasm
nuclear membrane starts to break down

Question 11

Metaphase

Answer 11

nuclear membrane fully broken down
chromosomes line up at equator
two fibres attach to each chromosomes

Question 12

Anaphase

Answer 12

fibres contract-each chromosome pulled apart
two strands pulled to opposite ends of the cell
each strand has identical genes-identical genes have been pulled to either side of the cell

Question 13

Telephase

Answer 13

nuclear membrane forms around each set of chromosomes

chromosomes elongate-chromatin

Question 14

function of mitosis in unicellular organisms

Answer 14

reproduction e.g. amoeba

Question 15

function of mitosis in multicellular organisms

Answer 15

growth of repair and cells

e.g. develops zygote into embryo

Question 16

cancer

Answer 16

group of disorders in which certain cells lose their ability to control both the rate of mitosis and the number of times mitosis takes place

Question 17

benign tumours

Answer 17

kind
cells stop dividing after some time
not life threatening
e.g. warts

Question 18

malignant tumours

Answer 18

abnormal cells

can invade other cells (metastasis)

Question 19

causes of cancer

Answer 19

normal genes are altered to form cancer causing genes (oncogenes)
brought about by carcinogens-cigarette smoke,UV

Question 20

treatment of cancer

Answer 20

surgery
radiation
chemotherapy

Question 21

meiosis

Answer 21

form of nuclear division in which the four daughter nuclei contain half the chromosome number of the parent nucleus

Question 22

functions of meiosis

Answer 22

sexual reproduction

new combinations of genes-variation

Question 23

meiosis-sexual reproduction

Answer 23

two haploid cells join together to form a diploid zygote

meiosis essential-halves chromosome numbers

Question 24

meiosis-variation

Answer 24

genes vary due to exchange of genetic material

Question 25

differences between mitosis and meiosis

Answer 25

mitosis:daughter cells have same number of chromosomes as parents
daughter cells have identical genes
two cells formed

meiosis:daughter cells have half the number of chromosomes as parents
different genes
four cells formed

Question 26

stages of mitosis

Answer 26

1. prophase
2. metaphase
3. anaphase
4. telephase

Question 27

centromere

Answer 27

point at which the chromosomes are attached in a double-stranded chromosome

Question 28

cell division in animal cells

Answer 28

cleavage-cleavage furrow appears around cell

becomes deeper until it eventually divides cytoplasm and splits cell in 2

Question 29

cell division in plant cells

Answer 29

rigid cell wall prevents cleavage furrow
vesicles gather in area between two nuclei
form cell plate