B5 Flashcards

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1
Q

Cells divide by two processes which are?

A

Mitosis and Meiosis

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2
Q

What do similar cells form?

A

Tissue

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3
Q

What do groups of tissues form?

A

Organ

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4
Q

What do groups of organs do?

A

Make up systems within the whole organism

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5
Q

List three reasons why Mitosis occurs?

A

For growth, repair and to replace old tissues

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6
Q

After Mitosis occurs, what does each new cell have?

A

Identical sets of chromosomes as the parent cell and the same number of chromosomes as the parent cell and the same genes as the parent cell

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7
Q

To enable Mitosis to take place, what do cells have to go through?

A

A cycle of growth and then division

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8
Q

What happens when the cell enters the growth phase of the cycle during Mitosis?

A

The number of organelles increase and the chromosomes are copied - the two strands of each DNA molecule separate and new strands form alongside

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9
Q

What two places does Meiosis only take place in?

A

Testes and ovaries

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10
Q

What does Meiosis produce?

A

Gametes for sexual reproduction

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11
Q

How many chromosomes do gametes contain?

A

Half the number of chromosomes as the parent cell

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12
Q

What happens during fertilisation?

A

A male gamete and a female gamete fuse together to produce a single boy cell, called a zygote

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13
Q

How many chromosomes does the zygote have?

A

One whole set of chromosomes because gametes only contain half the number of parent cells, so when both form together it creates a full set

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14
Q

In each new chromosome, how many chromosome come from each parent?

A

One chromosome from the father and one chromosome from the mother

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15
Q

When the zygote divides, what does it produce?

A

A cluster of cells called an embryo

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16
Q

Genes are present in the chromosomes in each cell nucleus. What do the genes control?

A

Growth and development in organisms and the development of characteristics

17
Q

How do genes control characteristics?

A

By providing instructions for the production of proteins

18
Q

The instructions used to help create characteristics are in the form of a code which is made up of four bases. These bases always pair up in what way?

A

Adenine (A) pairs with thymine (TY) and cytosine (C) pairs with guanine (G)

19
Q

DNA is too large to leave the nucleus meaning it has to stay inside. The production of proteins takes place outside the nucleus in the cytoplasm. How does this work?

A

Information stored in the genes has to be transferred into the cytoplasm

20
Q

How is information in the genes transferred to the cytoplasm?

A

1- The relevant section of DNA is unzipped
2- Instructions are copied onto smaller molecules called mRNA
3- These molecules leave the nucleus and carry instructions to the ribosomes
4- The ribosomes follow the instructions to make the relevant protein

21
Q

A group of three base pairs codes for one amino acid in a protein chain, called what?

A

A triplet code

22
Q

The structure of the protein depends on what?

A

The amino acids which make it up

23
Q

Up to the eight cell stage, all cells in a human embryo…?

A

Are unspecialised

Can have any gene switched on to form any kind of specialised cell

24
Q

After the eight cell stage, the cells in an embryo…?

A

Become specialised

Form different types of tissue

25
Q

Stem cells could potentially be used to…?

A

Help treat diseases and disorders

Repair damage to various tissues

26
Q

What are the three sources of stem cells?

A

1- Embryos
2- Blood from the umbilical chord
3- Adult stem cells from bone marrow

27
Q

What process do plant cells divide by?

A

Mitosis

28
Q

New cells in plants specialise into the cells of…?

A

Roots
Leaves
Flowers

29
Q

Which area of the plant does plant growth occur in?

A

Meristems - sites where unspecialised cells are dividing by mitosis

30
Q

What are the two types of meristem?

A

Lateral, which leads to increased girth

Apical, which leads to increased height in longer roots

31
Q

If the hormonal conditions in their environment are changed, the unspecialised plant cells can develop into other…?

A

Tissues - e.g xylem and phloem

Organs - e.g leaves, roots and flowers

32
Q

Xylem tubes are used by the plant to…?

A

Transport water and soluble mineral salts from the roots to the stem and leaves
Replace water lost during transpiration and photosynthesis

33
Q

What are phloem tubes used by the plant for?

A

To transport dissolved food to the whole pant for respiration or storage

34
Q

What is one way plants can be reproduced?

A

1 - Cuttings are taken from the plant
2 - The cuttings are put into a rooting hormone
3 - Roots start to form and the new plants develop

35
Q

When plants respond to light, they change direction in which they grow. What is this called?

A

Phototropism