Genes, chromosomes, cell division and variation

Question 1

What shape is DNA?

Answer 1

Double helix

Question 2

How many bases are there in DNA?

Answer 2

4

Question 3

Name the bases in DNA

Answer 3

Adenine, Cytosine, Guanine and Thymine

Question 4

Which bases pair with each other?

Answer 4

A with T, C with G (complimentary base paring)

Question 5

What is a gene?

Answer 5

A length of DNA which codes for a protein

Question 6

What do these proteins control?

Answer 6

Chemical reactions, growth, colouration and all inheritable characteristics

Question 7

What do chromosomes control?

Answer 7

a SET of characteristics e.g. eye colour, hair colour

Question 8

What is a chromosome?

Answer 8

Long strands of DNA wound up and compacted to make it smaller

Question 9

How many pairs of chromosomes do humans have?

Answer 9

23 pairs (46 chromosomes)

Question 10

What is the name of having two copies of a chromosome?

Answer 10

Diploid

Question 11

Some organisms contain one copy of each chromosome, what is this called?

Answer 11

Haploid

Question 12

XX = ??

Answer 12

Female

Question 13

XY = ??

Answer 13

Male

Question 14

Name 2 human haploid cells

Answer 14

Egg and sperm

Question 15

What are the two types of cell division?

Answer 15

Mitosis and meiosis

Question 16

Explain the process before cell division begins

Answer 16

Chromosomes replicate, making exact copy of themselves, doubles amount of DNA in cell

Question 17

What is mitosis used for?

Answer 17

Growth, repair and asexual reproduction

Question 18

What does mitosis produce?

Answer 18

Genetically identical (diploid) daughter cell

Question 19

What is meiosis used for?

Answer 19

ONLY used for producing gametes (sperm, eggs, pollen - not identical) for sexual reproduction

Question 20

What is meiosis?

Answer 20

Process by which we make genetically varied cells with half the number of chromosomes

Question 21

What is variation in offspring produced by?

Answer 21

1) genetic variation in gamete cells produced by meiosis

2) random fertilisation of ova by male gametes

Question 22

Mitosis vs meiosis: what they produce

Answer 22

• Mitosis: genetically identical daughter cells

- Meiosis: non-identical

Question 23

Mitosis vs meiosis: number of what they produce

Answer 23

• Mitosis: 2 cells

- Meiosis: 4 cells

Question 24

Mitosis vs meiosis: division

Answer 24

• Mitosis: 1 divison

- Meiosis: 2 divisions

Question 25

Mitosis vs meiosis: haploid or diploid in humans?

Answer 25

- Mitosis: diploid | - Meiosis: haploid

Question 26

Mitosis vs meiosis: number of chromosomes

Answer 26

- Mitosis: keeps same number | - Meiosis: halves number

Question 27

Mitosis vs meiosis: where it occurs in humans

Answer 27

- Mitosis: throughout human body | - Meiosis: in ovary and testis

Question 28

Mitosis vs meiosis: where it occurs in plants

Answer 28

- Mitosis: throughout plant | - Meiosis: ovary and anther

Question 29

Mitosis vs meiosis: sexual or asexual reproduction?

Answer 29

- Mitosis: asexual | - Meiosis: sexual

Question 30

What is variation?

Answer 30

The difference between individuals

Question 31

3 causes of variation

Answer 31

Genetic, environmental or combination of both

Question 32

What is a mutation?

Answer 32

A change in the DNA

Question 33

Chromosomal mutation?

Answer 33

When a cell gains an extra chromosome or one part of a chromosome is stuck onto another

Question 34

Sequence mutation?

Answer 34

A change in the sequence by replacing a single base pair with a different pair - changes sequence of amino acids in the encoded protein (effects protein shape)

Question 35

3 possible outcomes of mutations

Answer 35

Positive, negative and neutral

Question 36

What are mutagens?

Answer 36

Chemicals which cause more frequent mutations