Cells

Question 1

organelle

Answer 1

a part of a cell with a specialized function

Question 2

labelled diagram of the cell

Answer 2

Question 3

algae

Answer 3

informal term for a large and diverse group of photosynthetic eukaryotic organisms

Question 4

Petri dish

Answer 4

is a shallow transparent lidded dish that biologists use to hold a growth medium in which cells can be cultured, originally, cells of bacteria, fungi and small mosses.

Question 5

trichocyst

Answer 5

organelle found in certain single-celled eukaryotes

Question 6

haemoglobin

Answer 6

protein that transports oxygen

Question 7

eukaryote

Answer 7

cell with a nucleus (and other organelles)

Question 8

meiosis

Answer 8

one diploid nucleus divides to produce four haploid (genetically different) nuclei; meiosis produces germ (sex) cells (eggs and sperm)

Question 9

mitosis

Answer 9

division of the nucleus into two genetically identical daughter nuclei, allows the cell to divide into two daughter cells with the same DNA

Question 10

diploid

Answer 10

having pairs of homologous chromosomes

Question 11

haploid

Answer 11

haveing only one chromosome of each pair

Question 12

Explain how the cell cycle is controlled

Answer 12

Question 13

cladogram

Answer 13

tree diagrams that show the most probable sequence of divergence in clades

Question 14

clade

Answer 14

group of organisms evolved from a common ancestor is called a clade

Question 15

Why are cladograms based on DNA sequences more reliable than cladograms based on protein sequences?

Answer 15

several different triplets of DNA can code for the same amino acid

Question 16

During part of the cell cycle is DNA replciated?

Answer 16

Interphase

Question 17

Stages of mitosis

Answer 17

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

Question 18

prophase

Answer 18

1. chromosomes become shorter and fatter by coiling
2. nucleolus breaks down
3. microtubules grow from microtubule organizing centres
4. nuclear membrane breaks down

Question 19

metaphase

Answer 19

1. microtubules continue to grow and attach to the centromeres
2. chromosomes align on metaphase plate
3. spindle fibres (one from each pole) attach to opposite sides of each centromere

Question 20

anaphase

Answer 20

1. each centromere divides
2. the pairs of sister chromatids separate
3. spindle microtubules pull them rapidly towards the poles of the cell
4. mitosis produces two genetically identical nuclei because sister chromatids are pulled to opposite poles

Question 21

telophase

Answer 21

1. chromatids have reached
   the poles (therefore now called
   chromosomes)
2. at each pole the
   chromosomes are pulled into a
   tight group
3. nuclear membrane reforms
   around them
4. chromosomes uncoil
5. nucleolus is formed

Question 22

cytokinesis

Answer 22

formation of new cell membranes around the daughter cells

Question 23

interphase

Answer 23

1. consists of three phases
   
   • G₁
   • S
   • G₂
2. replication of DNA during S phase
3. copied chromosomes are called sister chromatids and are bound together at centromere

Question 24

mitotic spindle

Answer 24

microtubles that connect to centromeres