Cell Division

Question 1

What is interphase?

Answer 1

Chromatin into chromosomes, DNA replication, centriole replication

Question 2

What is a centriole and spindle fibres and where is it found?

Answer 2

Located at the two poles of the cell, uses spindle fibres to pull chromosomes around
Only in animal cell, not plant
Spindle fibres attached to the kineticore of the centromere of the chromosome and the centriole at two poles of the cell, used to move the chromosomes

Question 3

What are sister chromatids?

Answer 3

Genetically identical DNA parts of a chromosome (one line of an X)

Question 4

What are homologous chromosomes?

Answer 4

Contain the same genes but different alleles (one maternal one paternal)

Question 5

What are somatic cells?

Answer 5

Non-reproductive cells

Question 6

Define mitosis

Answer 6

A nucleus division that produces 2 genetically identical daughter nuclei with the same number of chromosomes

Question 7

Describe mitosis and all its stages

Answer 7

Prophase: chromatin condenses and shortens to form chromosomes, spindle fibres form and attach to the centrioles and the kineticore in the centromere
Metaphase: the chromosomes line up along the equator
Anaphase: pulled apart to the two different poles of the equator
Telephase: spindle fibres break down, nuclear envelope reforms, chromosomes uncoil to form chromatin, cytokinesis also occurs (cleavage furrow for animals, cell plate for plants)

Question 8

What is the importance of mitosis?

Answer 8

RAG: Repair (replace old worn cells), asexual reproduction (genetically identical offspring), growth (increase in cell numbers)

Question 9

What is cytokinesis? In animal and plant cells

Answer 9

The cytoplasm of the cells splits, happens with telophase

Animal: cleavage furrow forms
Plant: cell plate forms

Question 10

Define meiosis

Answer 10

Nuclear division that produces 4 daughter nuclei that are genetically dissimilar and have half the number of chromosomes as the parent nuclei

Question 11

What does meiosis form/create?

Answer 11

Gamates (sex cells)

Question 12

What are haploid and diploid numbers?

Answer 12

Haploid: number of chromosomes in daughter (n)
Diploid: number of chromosomes in parent (2n)

Question 13

Importance of meiosis

Answer 13

Gamate fertilisation restores diploid number (2n) in zygote, prevents doubling of chromosome number during fertilisation
Ensures genetic variation

Question 14

Genetic variation in meiosis

Answer 14

VIRGo: Variation— Independent assortment, random fertilisation, genetic recombination
Random fertilisation: each gamate has a unique set of maternal and paternal chromosomes
Genetic recombination crossing over: prophase 1, when they pair up homologous chromosomes and genetic recombination occurs, abit of gene exchange
Independent assortment during metaphase 1: random lining up, gamates with random mix of paternal and maternal chromosomes

Question 15

Functions of each of the 2 meiosis divisions

Answer 15

Meiosis 1: separate homologous chromosomes

Meiosis 2: separate sister chromatids

Question 16

What is synapsis?

Answer 16

When homologous chromosomes pair up in prophase 1

Question 17

What is another name for the equator of the cell?

Answer 17

The metaphase plate

Question 18

Chromatin or chromosomes during interphase?

Answer 18

Chromatin, so DNA polymerase has more surface area to work on to make more DNA

Question 19

What is nondisjunction?

Answer 19

Failure of sister chromatids to separate during anaphase 2, one more/less chromosome in each cell

Question 20

Describe the features of homologous chromosomes

Answer 20

Same size
Same position of centromere
Same genes at the same positions
One maternal, one paternal

Question 21

What is the kinetichore?

Answer 21

The part of the centromere where spindle fibres attach to the chromosomes

Question 22

What happens during prophase?

Answer 22

Chromatin condenses and shortens to form chromosomes
Nuclear envelope breaks down
Spindle fibres form, connecting kinetochore of centromere of each chromosome (to centriole in animal cells)

Question 23

What happens during metaphase?

Answer 23

Chromosomes line up along the equator (metaphase plate)

Question 24

What happens during anaphase?

Answer 24

Spindle fibres shorten, pulling chromatids apart to opposite ends of the cell

Question 25

What happens during telophase / cytokinesis?

Answer 25

Spindle fibres break down
Chromosomes uncoil to form chromatic
Nuclear envelope reforms around chromosomes
Cytoplasm divided into half, by cleavage furrow in animal cells and cell plate in plant cells