Exam B6

Question 1

DNA

Answer 1

double helix found in chromosomes.

Question 2

Gene

Answer 2

small section of DNA that codes for a protein

Question 3

Inheritance

Answer 3

Humans have 23 pairs of chromosomes.

Question 4

Allele

Answer 4

different versions of the same gene.

One from mum, one from dad.

Question 5

Dominant

Answer 5

always shows (B)

Question 6

Recessive

Answer 6

only shows if both alleles are recessive (b)

Question 7

Cystic fibrosis: caused by a

Answer 7

recessive allele

Question 8

Polydactyly extra fingers caused by a

Answer 8

dominant allele

Question 9

Genetic Diagrams (Punnett Squares)

Answer 9

Question 10

Cystic fibrosis

Answer 10

recessive

Question 11

Polydactyly extra fingers caused by a

Answer 11

dominant allele

Question 12

Genetic Diagrams (Punnett Squares)

Answer 12

Question 13

Fossils don’t form in

Answer 13

Soft tissue

Question 14

GM crops can increase

Answer 14

yield and resist disease

Question 15

What is Reproduction?

Answer 15

Reproduction is the process of making new organisms (offspring).

Question 16

Asexual Reproduction

Answer 16

• Only 1 parent
• No fusion of gametes
• No variation – all offspring are genetically identical (clones)
• Happens by mitosis

Question 17

Example of Asexual Reproduction

Answer 17

• Bacteria
• Strawberry runners
• Some fungi (like mould)

Question 18

Sexual Reproduction

Answer 18

• 2 parents
• Involves fusion of male and female gametes (e.g. sperm + egg)
• Offspring show variation
• Uses meiosis to make gametes

Question 19

What is the two types of Reproduction?

Answer 19

Asexual Reproduction
Sexual Reproduction

Question 20

Gametes and Fertilisation

Answer 20

Flowers

Question 21

What is Fertilisation

Answer 21

when the nuclei of two gametes join to form a zygote (fertilised egg)

Question 22

Meiosis (Only in Sexual Reproduction)

Answer 22

• Makes gametes (sperm, egg, etc.)
• Chromosome number halves
• Introduces genetic variation

Question 23

Steps of Fertilisation

Answer 23

Zygote → embryo → baby

Question 24

Sexual Reproduction example

Answer 24

• Humans and animals
• Flowering plants (egg + pollen)

Question 25

Human cells:

Answer 25

• Normal cells = 46 chromosomes (23 pairs) • Gametes = 23 chromosomes

Question 26

Advantages & Disadvantages Of asexual and sexual

Answer 26

Question 27

Asexual reproduction =

Answer 27

no variation (clones)

Question 28

Meiosis makes gametes with half….

Answer 28

half the chromosomes

Question 29

Sexual reproduction =

Answer 29

variation due to mixing of genes

Question 30

Dose Bacteria reproduce asexually or sexually

Answer 30

Bacteria reproduces asexually no sperm or egg involved

Question 31

What is asexual reproduction?

Answer 31

Reproduction with one parent and no gametes; offspring are clones.

Question 32

Fertilisation restores full number of chromosomes (back to 46 in humans)

Answer 32

Fertilisation restores full number of chromosomes (back to 46 in humans)

Question 33

Advantages & Disadvantages Of asexual and sexual

Answer 33

Question 34

What is sexual reproduction?

Answer 34

Reproduction involving two parents and the fusion of gametes.

Question 35

What is fertilisation?

Answer 35

When the nuclei of a sperm and egg fuse to form a zygote

Question 36

What is a gamete?

Answer 36

A sex cell (e.g. sperm, egg, pollen, ovule).

Question 37

How many chromosomes in a human gamete?

Answer 37

23

Question 38

What type of cell division makes gametes?

Answer 38

Meiosis

Question 39

Name two organisms that reproduce asexually

Answer 39

Bacteria and fungi

Question 40

What is Meiosis?

Answer 40

Meiosis is a type of cell division that: • Only happens in sexual reproduction • Produces gametes (sperm and egg cells) • Each gamete has half the number of chromosomes

Question 41

Where does it happen? Meiosis

Answer 41

• In the testes (to make sperm) • In the ovaries (to make eggs) • In flowers (to make pollen and ovules)

Question 42

Why is Meiosis important?

Answer 42

Meiosis: • Makes gametes • Each gamete has 23 chromosomes (instead of 46) • So that when fertilisation happens, the zygote ends up with 46 chromosomes

Question 43

What is Gametes

Answer 43

haploid (half the DNA)

Question 44

What is zygote

Answer 44

diploid (normal number)

Question 45

What happens during meiosis?

Answer 45

1. A cell with 46 chromosomes copies its DNA. 2. Then it divides twice to make 4 gametes. 3. Each gamete: • Is genetically different • Has 23 chromosomes

Question 46

Why does this cause variation?

Answer 46

Each gamete is genetically different — this causes genetic variation in offspring (a key advantage of sexual reproduction).

Question 47

Difference Between Mitosis and Meiosis

Answer 47

Question 48

Meiosis =

Answer 48

gametes made, not body cells

Question 49

Gametes have….

Answer 49

23 chromosomes, not 46

Question 50

Meiosis = 4 non or identical cells

Answer 50

4 non-identical cells ✅ Happens in testes and ovaries, not everywhere ✅ Leads to variation ✅ Meiosis = 2 divisions

Question 51

What is meiosis used for?

Answer 51

Making gametes (sex cells)

Question 52

How many divisions happen in meiosis?

Answer 52

Two

Question 53

How many cells are made in meiosis?

Answer 53

4

Question 54

Are the cells made by meiosis identical?

Answer 54

No — they are genetically different

Question 55

Meiosis look like

Answer 55

Question 56

Advantages & Disadvantages Of asexual and sexual

Answer 56

Question 57

Dose gametes contain a single chromosome

Answer 57

Yes they do

Question 58

In gametes are the chromosomes paired yes or no

Answer 58

They are not paired they single

Question 59

Meiosis steps free siencelessons

Answer 59

1. All of the chromosomes are copied 2.the cell now divides into two 3.now both of the cells divide one more time forming the gametes In the gametes the chromosomes are now single not paired

Question 60

Each gametes have different..

Answer 60

Alleles

Question 61

Meiosis halves the number of…

Answer 61

Chromosomes and produces gametes

Question 62

In sexual reproduction the gametes…

Answer 62

Join together Scientists call this fertilisation

Question 63

In fertilisation the full number of chromosomes is….

Answer 63

Restored

Question 64

What happened after fertilisation

Answer 64

Now the new cell divides by mitosis producing a clump of identical cells