Ch 2

Question 1

Cell cycle

Answer 1

Division of one cell into another
G1 - active growth
S - DNA synthesis
G2 - preparation for devision
Mitosis - devision
Cytokinesis - final separation into two cells

Question 2

Mitosis interphase

Answer 2

Chromosomes not visible
Centriole are visible
Chromatin becomes shorted and thicker

Question 3

Mitosis prophase

Answer 3

Chromatin condenses more forming 2 chromatids held at a centromere
Spindle fibers form
Nucleolus disappears
Nuclear membrane breaks down

Question 4

Mitosis metaphase

Answer 4

Spindle fibers move chromatids to metaphase plate

Question 5

Mitosis anaphase

Answer 5

Spindle fibers pull chromatids apart (become chromosomes) at Centromere to opposing poles

Question 6

Mitosis telophase

Answer 6

Chromosomes decondense and become less visible
New nuclear envelope forms
Nucleoli reforms
Spindle disassembles

Question 7

Cytokinesis in animal cells

Answer 7

Division of cytoplasm after mitosis
Membrane pinches in the middle forming a cleavage furrow

Question 8

Cytokinesis in plant cells

Answer 8

Division of cytoplasm after mitosis
Vesicles accumulate at cell plate and fuse which ceperates cytoplasm by creating a new cell wall

Question 9

Binary fission

Answer 9

Reproduction of cells in prokaryotes
Produces 2 identical daughter cells

Question 10

Allele

Answer 10

The alternative versions of the same gene
Eg blue eyes and brown eyes

Question 11

Karyotype

Answer 11

The standard graphical image used to display and analyse chromosomes

Question 12

What is synapsis

Answer 12

Pairing of homologous chromosomes during prophase

Question 13

What’s a tetrad

Answer 13

4 sister chromatids consisting of 2 homologous pairs
l l l l
X X

Question 14

What happens during crossing over

Answer 14

DNA which has gone through crossing over during prophase 1 where alleles swap in homologous chromosomes (when they have formed a tetrad)

Question 15

Define binary fission

Answer 15

The process of asexual reproduction where prokaryotic cells divide into two identical daughter cells

Question 16

What are the stages of mitosis

Answer 16

interphases
prophase
metaphase
anaphase
telophase

Question 17

what’s a centromeres purpose in mitosis

Answer 17

the position on chromosomes where spindle fibres attach

Question 18

what are the 4 ways to describe the position of a centromere on a chromosome

Answer 18

metacentric – in the middle
submetacentric – between the middle and the ends
acrocentric – closer to the ends
telocentric - at the end

Question 19

What are the steps of meiosis

Answer 19

Meiosis I
- Prophase I
- Metaphase I
- Anophase I
- Telophase I
Cytokinisis
Metaphase II
- Prophase II
- Metaphase II
- Anophase II
- Telophase II
Cytokinesis

Question 20

what does meiosis produce

Answer 20

4 daughter cells/gametes

Question 21

Prophase II

Answer 21

spindle forms at right angles to the first one

Question 22

Anaphase II

Answer 22

chromatids separate & move to poles

Question 23

Metaphase II

Answer 23

chromosomes move to equator

Question 24

Telophase II

Answer 24

spindle fibers disappear, chromosomes de-condense, nuclear envelope & nucleoli form

Question 25

Apoptosis

Answer 25

the programming of cells to self-destruct
e.g. skin cells are 3 weeks

Question 26

what can an organism do to remove muted or damaged cells?

Answer 26

Activate apoptosis

Question 27

what’s the process called where a cells nucleus is dismantled and its membrane blebs

Answer 27

apoptosis

Question 28

what can happen if apoptosis fails

Answer 28

Cancer:
some tumour cells don’t have the suicide gene, and grow & divide uncontrollably

Question 29

what happens during fertilisation

Answer 29

haploid egg (n) & sperm (n) fuse to produce a diploid zygote (2n)
23 chromosomes + 23 chromosomes = 46 chromosomes