National 5 Biology | Unit 2 | Key Area 1: Producing New Cells

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What is growth? (2)

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Biology

10th

30 Terms

1

What is growth? (2)

-Increase in size (of individual cells or whole organisms)

-Increase in cell number (as a result of cell division)

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2

What is cell division vital for? (4)

-In multicellular organisms, it allows an individual to increase the number of its cells (ie. growth)

-In multicellular organisms, it allows an individual to replace dead cells

-In some unicellular organisms, it is a method for asexual reproduction

-The process of meiosis (production of sex cells, ie. sexual reproduction)

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3

Cell division consists of two stages:

  1. The nucleus divides (mitosis)

  2. The cytoplasm divides

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4

The stages of mitosis are:

Prophase, metaphase, anaphase, telophase

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5

Describe stage 1 of mitosis:

  1. Chromosomes in the parent cell replicate and form two chromatids joined by a centromere

  2. The nucleus becomes larger

  3. Chromosomes shorten and thicken (condense) and become visible for a short time

  4. The nuclear membrane breaks down and disappears

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6

Describe stage 2 of mitosis:

  1. A spindle appears inside the nucleus (fibres of protein)

  2. The chromosomes are lined up across the equator of the cell

  3. The chromosomes become attached to the spindle by their centromeres

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7

Describe stage 3 of mitosis:

  1. The centromeres of the chromosomes divide, and the half-centromeres repel each other

  2. The spindle fibres contract and pull the chromatids of each chromosome apart towards the poles

(Chromatids become chromosomes after they separate)

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8

Describe stage 4 of mitosis:

  1. The spindle breaks down

  2. The separated chromosomes gather at each pole and new nuclear membrane forms around them

  3. The chromosomes uncoil and become invisible again

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9

After mitosis, the cytoplasm _____ by forming new _____ _____ between the separated nuclei.

Divides; cell membrane

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10

After mitosis, why is DNA copied?

It allows one chromosome to consist of two chromatids, so that cell division can occur again. It ensures that each daughter cell receives one identical copy of the genetic information.

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11

Human cells contain _____ chromosomes made up of _____ pairs. Cells which contain 2 sets of each chromosome like this are said to be _____.

46; 23; diploid

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12

Sex chromosomes

One of the chromosome pairs that determine the sex of an individual.

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13

In females, the sex chromosomes are:

XX

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14

In males, the sex chromosomes are:

XY

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15

Haploid cells

Cells that only have one set of chromosomes from each pair of chromosomes, such as gametes (sex cells, eg. sperm and ova)

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16

Diploid cells

Cells that have two matching sets of chromosomes. In humans, there are 23 types of chromosome, and since human cells (apart from gametes) are diploid, we have 46 chromosomes in each cell.

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17

Diploid cell compliment

The total number of chromosomes in two complete sets.

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18

Stem cells

Unspecialised cells which can divide to produce new stem cells. They are involved in the growth and repair of the body.

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19

Explain the self-renewal aspect of a stem cell:

Stem cells can undergo repeated divisions, thus maintaining a pool of unspecialised cells.

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20

Explain the differentiation aspect of stem cells:

Stem cells have the potential to specialise, ie. differentiate into any type of specialised cell in the body.

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21

Embryonic stem cells

Stem cells present in the blastocyst (formed after a zygote divides to form a clump of cells). Their function is to produce every cell type needed to make up the human body.

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22

Adult stem cells

Stem cells found in nearly all tissue types in the human body. Their function is to replace damaged cells and repair damaged tissues.

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23

Unlike embryonic stem cells, adult stem cells can only _____ into a _____ number of specialised cells. These are normally only the cell types that make up the tissue in which they are found.

Differentiate; limited

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24

_____ _____ contains the highest number of stem cells. There are very few stem cells found in the _____ and _____. The spinal cord is unable to regenerate due to the lack of stem cells.

Bone marrow; brain; heart

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25

If tissue is healthy, adult stem cells will remain _____ and do not _____. Self-renewal is triggered when tissues are damaged by injury or disease.

Inactive; divide

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26

Tissue

A group of specialised cells

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27

Organ

A group of tissues

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28

System

A group of organs working together

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29

Organism

A group of systems working together

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30

The hierarchy of organ systems are (smallest-largest):

Cells, tissues, organs, systems, organisms

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