7 - DNA, Genes and Chromosomes Flashcards Preview

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Flashcards in 7 - DNA, Genes and Chromosomes Deck (85)
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1

What does the nucleus contain?

Genetic information in the form of chromosomes

2

What are chromosomes?

Long lengths of DNA coiled up

3

What does diploid mean?

There are two copies of each chromosomes arranged in pairs
Human nucleus - 46 chromosomes, 23 pair
Human diploid number - 46

4

What is DNA?

- A long list of instructions on how to put an organism together and make it work
- A type of nucleic acid
- Each separate gene in a DNA molecule is a chemical instruction that codes for a particular protein
- Each molecule is two strands coiled together to make a double helix

5

Why are proteins important?

- Control most of the processes in the body
- Determined inherited characteristics

6

What are genes?

Chemical instructions that control proteins

7

What are alleles?

Different versions of the same gene

8

What are bases?

Chemicals that hold DNA together
A - Adenine
C - Cytosine
G - Guanine
T - Thymine
Paired complimentarily (A-T and C-G)

9

What is asexual reproduction?

Involves only one parent. The offspring have identical genes to the parent so there is no variation between parent and offspring
Done through Mitosis

10

What is mitosis?

When a cell reproduces itself by splitting to form two cells with identical sets of chromosomes
Used in asexual reproduction and growth and repair

11

Describe mitosis

- In a cell that is not dividing the DNA is spread out in long strings
- The cell gets a signal to divide and the duplicates its DNA so there is one copy for the new cells
- DNA forms x-shaped chromosomes
- Line up in the middle of the cell and are pulled apart by cell fibres
- Membranes form around each of the sets of chromosomes and become the new nuclei of the cells
- The cytoplasm divides
- There is now two identical cells

12

Describe mitosis

- In a cell that is not dividing the DNA is spread out in long strings
- The cell gets a signal to divide and the duplicates its DNA so there is one copy for the new cells
- DNA forms x-shaped chromosomes
- Line up in the middle of the cell and are pulled apart by cell fibres
- Membranes form around each of the sets of chromosomes and become the new nuclei of the cells
- The cytoplasm divides
- There is now two identical cells

13

What is sexual reproduction?

The fusion of male and female gametes. Because there are two parents the offspring contain a mixture of their genes

14

What are gametes?

Sperm and egg cells

15

What does haploid mean?

Only half the number of chromosomes
Each gamete has 23 chromosomes - so the haploid number is 23

16

What is fertilisation?

When a male gamete fuses with a female gamete to form a zygote (which has a full set of chromosomes)

17

What is a zygote?

The product of fertilisation which undergoes cell division by mitosis to form an embryo

18

What is meiosis?

Cell division which produces four haploid cells whose chromosomes are not identical

19

Describe meiosis

- The cell duplicates its DNA and lines up in the centre of the cell
- The pairs are pulled apart so each new cell has one copy of each chromosome
- Each new cell will have a mixture of the mother's and father's chromosomes which creates variation
- The cells line up in the centre again and are pulled apart
- Produces four haploid cells which has a single set of chromosomes and are genetically different

20

What is the stamen?

The male reproductive part of a plant
Consists of the anther and filament

21

What is the role of the anther?

Contains pollen grains which produce the male gametes (sperm)

22

What is the role of the filament?

The stalk that supports the anther

23

What is the carpel?

The female reproductive part of a plant
Consists of the stigma, style and ovary

24

What is the role of the stigma?

The end bit that pollen grains stick to

25

What is the role of the style?

The rod-like section that supports the stigma

26

What is the role of the ovary?

Contains the female gametes (eggs)

27

What is pollination?

The transfer of pollen from the anther to the stigma so the male gametes can fertilise the female gametes in sexual reproduction

28

What is cross-pollination?

A type of sexual reproduction where pollen is transferred from the anther of one plant to the stigma of another
Relies on wind and insects

29

What are adaptations for insect pollination?

- Bright colours
- Scented flowers and nectaries
- Big, sticky pollen grains to stick to insects
- Sticky stigma so pollen will stick to it

30

What are nectaries?

Glands that secrete nectar