D2.1 Cell & nuclear division

Question 1

Mitosis

Answer 1

Reproduction of the nucleus

Question 2

Cytokinesis

Answer 2

Division of the cytoplasm

Question 3

Diploid

Answer 3

Cells that have 2 sets of chromosomes (46)

Question 4

Haploid

Answer 4

Cells that have 1 set of chromosomes (23)

Question 5

Somatic cells

Answer 5

Cells that only undergo mitosis

Question 6

Binary fission

Answer 6

Division of one cell reproduces the entire organism

Question 7

The original cell before replication is also called…

Answer 7

Parent or mother cells

Question 8

What is the new cell replicated from the original cell called?

Answer 8

Daughter cells

Question 9

How does cell division work?

Answer 9

1. DNA replication
2. Mitosis — produce 2 genetically identical cells
3. Meiosis — Splits into 2 diploid cells

Question 10

What happens during interphase?

Answer 10

Produce RNA & synthesise proteins / enzymes
—> prepare for duplication

Question 11

What are the 4 phases of mitosis

Answer 11

Prophase
Metaphase
Anaphase
Telophase

Question 12

Mitosis

Answer 12

Dividing the cell’s DNA between 2 daughter nuclei

Question 13

What happens in prophase?

Answer 13

• Nuclear membrane disintegrates
• Doubled chromosomes condense & shorten
• BEGIN to move to the equator

Question 14

What happens during metaphase?

Answer 14

• Chromosomes align along middle of cells
• “Meta” = middle
• Spindle fibres coordinate movement — helps insure nucleus only receives 1 copy of each chromosome

Question 15

What happens during anaphase?

Answer 15

• Sister chromatids separate at kinetochores
• Move to opposite poles
• Pulled at centromeres
• Pulled by motor proteins “walking” along microtubules (actin, myosin)
• poles move farther apart

Question 16

What happens during telophase?

Answer 16

• Chromosomes arrive at opposite poles
• daughter nuclei form, nucleoli form, chromosomes disperse (no longer visible under light microscope)
• Spindle fibres disperse
• Cytokinesis begins (cell division)

Question 17

How does cytokinesis work in animals?

Answer 17

1. Constriction belt of actin microfilaments around equator of cell
2. Cleavage furrow forms
3. Splits cell in 2

Question 18

How does cytokinesis work in plants?

Answer 18

1. Cell plate forms
2. New cell wall laid down between membranes
3. New cell wall fuses with existing cell wall

Question 19

How does reproduction through mitosis work?

Answer 19

1. Budding — forms new organism from a small projection growing on the surface of the parent
2. Fragmentation — splitting of the parent into pieces that grow into a new organism
3. Vegetative reproduction — forms new plant from the modification of a stem or underground structure on the parent plant

Question 20

What is asymmetric cell division composed of?

Answer 20

Cell polarisation & Cytokinesis

Question 21

What role does asymmetric cell division have?

Answer 21

• Generate cell diversity during development
• Decision of stem cells to undergo self renewal

Question 22

How is sperm & egg produced?

Answer 22

Reduce 46 chromosomes
—> Half number of chromosomes

Question 23

Meiosis reduces chromosome number from ______ to ______ (humans)

Answer 23

Diploid to haploid (2n —> n)

Question 24

Fertilisation restores chromosome number from _____ to ____ (humans)

Answer 24

Haploid to diploid (n —> 2n)

Question 25

Describe the double division of meiosis

Answer 25

1. DNA replication 2. 1st division - separates homologous pairs 3. 2nd division - separates sister chromatids

Question 26

Difference in processes in meiosis 1 & 2

Answer 26

1. Interphase — Prophase 1 — Metaphase 1 — Anaphase 1 — Telophase 1 2. Prophase 2 — Metaphase 2 — Anaphase 2 — Telophase 2

Question 27

Why is meiosis valued?

Answer 27

introduces genetic variation

Question 28

Genetic variability in sexual reproduction is seen through…

Answer 28

1. Independent assortment — homologous chromosomes (meiosis 1) 2. Crossing over — homologous chromosomes (prophase 1) 3. Random fertilisation — random ovum & sperm

Question 29

Problems with meiosis spindle cause errors in…

Answer 29

Daughter cells

Question 30

Too many or too few chromosomes is called…

Answer 30

Aneuploidy (type of nondisjunction)

Question 31

What are the types of nondisjunction?

Answer 31

- Euploidy = correct number of chromosomes - Anueploidy = change in chromosome number due to nondisjunction in meiosis - Trisomy = cells have 3 copies of a chromosome - Monosomy = cells only have 1 copy of a chromosome

Question 32

Down syndrome is caused by…

Answer 32

3 copies of chromosome 21 (Trisomy 21)

Question 33

Down syndrome causes…

Answer 33

- Delayed mental & social skills - Decreased muscle tone at birth - Asymmetrical or odd shaped skull - Small skull - Broad, short hands - Increased risk of Leukaemia & Alzheimer’s (later in life)

Question 34

What is spermatogenesis?

Answer 34

Continuous & prolific process

Question 35

What is oogenesis?

Answer 35

Unequal cytokinesis