Meoisis

Question 1

What number of chromosomes do normal body cells have

Answer 1

Haploid
2 of each chromosome
1 maternal and 1 paternal

Question 2

What number of chromosomes do gametes have

Answer 2

Diploid

1 copy of each chromosome

Question 3

How does random fertilisation help genetic diversity

Answer 3

Produces zygotes with different combinations of chromosomes from both parents

Question 4

Where does meiosis happen

Answer 4

Reproductive organs

Question 5

What happens before meiosis

Answer 5

DNA unravels and replicates and condenses
Forming 2 copies of each chromosome = chromatids
The sister chromatids join by a centromere

Question 6

What happens in meiosis 1

Answer 6

Chromosomes arrange in homologous pairs
Homologous pairs are separated
Halving the number of number of chromosomes

Question 7

What happens in meiosis 2

Answer 7

The pairs of sister chromatids are separated

As the centromere divides

Question 8

What is the product if Meiosis

Answer 8

4 genetically different haploid cells

Question 9

How is genetic diversity created In meiosis 1

Answer 9

Crossing over
And
Independent segregation

Question 10

Explain crossing over

Answer 10

In meiosis 1
Homologous pairs pair up 
The chromatids twist around each other 
Exchanging alleles 
So the chromatids have different alleles

Question 11

Explain independent segregation

Answer 11

In meiosis 1
Random as to what cells receive the maternal or paternal chromosome
So the 4 daughter cells have different combinations of maternal and paternal chromosomes

Question 12

Difference between mitosis and meiosis

Answer 12

Mitosis = daughter cells have same number of chromosomes as parent cell. The daughter and parent cells are all genetically identical. Produces 2 daughter cells 
Meiosis = daughter cells have half the number of chromosomes as the parent cell. All daughter cells and parent cells are genetically different. Produces 4 daughter cells

Question 13

What is chromosome mutations

Answer 13

Daughter cells have variations in the number of whole or parts of chromosomes

Question 14

Why do chromosome mutations lead to inherited disorders

Answer 14

The errors are present in the gametes

Question 15

What is non disjunction

Answer 15

The failure of chromosomes to separate

Question 16

What causes Down’s syndrome

Answer 16

The non disjunction of chromosome 21
So 1 cell has an extra copy of c21 and 1 cell has no copy
When the gametes fuse the zygote has an extra chromosome

Question 17

What is gene mutations

Answer 17

Change in the dna base sequence

Question 18

What is substitution mutation

Answer 18

A base is substituted

Question 19

What is a deletion mutation

Answer 19

A base is deleted

Question 20

How do mutation affect cell function

Answer 20

The order of dna bases determines the order of amino acid they code for
If a mutation happens the sequence of amino acids changes
Changing the primary and tertiary structure of the protein
Hanging its shape and function

Question 21

How is dna degenerate

Answer 21

1 amino acid is coded for by different dna triplets

Question 22

Why does not all mutations result in a change in amino acid sequences

Answer 22

Dna is degenerate
So the mutation still coded for the same amino acid
It was a substitution mutation

Question 23

Why do deletion mutations always result in a mutation

Answer 23

Change the number of bases present
Causing a frame shift in the bases after it
So more than 1 amino acid will change

Question 24

How do mutations happen

Answer 24

Spontaneously by a mistake in dna replication

Question 25

Give 4 examples of mutagenic agents

Answer 25

UV radiation
Ionising radiation
Toxic chemicals
Viruses