Genetic Information And Reltionships - Meiosis And Mutation

Question 1

Chromosome definition

Answer 1

An independent DNA molecule

Question 2

Gene definition

Answer 2

A base sequence of DNA that codes for a polypeptide or functional RNA

Question 3

Allele definition

Answer 3

Different forms of the same gene

Question 4

Locus definition

Answer 4

The fixed position of a gene on a particular chromosome

Question 5

Homologous chromosomes definition

Answer 5

A pair of chromosomes which have the same genes at thee same gene loci but may have different alleles

Question 6

Haploid cell definition

Answer 6

A cell containing one of each type of chromosome (n) e.g. a gamete

Question 7

Diploid cell definition

Answer 7

A cell containing two of each type of chromosome as pairs (2n) e.g normal body cell

Question 8

(N) meaning

Answer 8

The number of types of chromosomes in a cell

Question 9

(2n) meaning

Answer 9

The total number of chromosomes in a diploid cell

Question 10

What is a mutation

Answer 10

A change in the sequence of DNA bases

Question 11

How does a mutation arise

Answer 11

Mutations can arise spontaneously during DNA replication and and include base deletion and base substitution

Question 12

What is a substitution mutation

Answer 12

One base is swapped with another different base

Question 13

What is a deletion mutation

Answer 13

One base is removed from the sequence

Question 14

What are the possible effects of a substitution mutation on a protein

Answer 14

Sometimes none because of the degenerate nature of the genetic code

Question 15

What is the effect of a deletion mutation on a protein

Answer 15

There is always an effect because the election of a base will cause a frame shift in all the base triplets after it

Question 16

Name some possible mutagenic agents

Answer 16

Ionising radiation, UV radiation, some viruses, some chemicals

Question 17

What is the role of mutagenic agents

Answer 17

Mutgenic agents increase the rate of chance of mutations

Question 18

What happens during crossing over

Answer 18

• Homologous chromosomes come together as a pair formimg a bivalent
• Non-sister chromatids cross over
• The point of the cross is called chiasmata
• Getenic information is swapped

Question 19

How does crossing over increase genetic variation

Answer 19

The resulting chromatids after crossing over contain the same genes but have a different combination of alleles

Question 20

What is crossing over

Answer 20

The swapping of genetic information between homologous pairs of chromosomes

Question 21

What is independent segregation

Answer 21

The random positioning of homologous pairs

Question 22

What happens during independent segregation

Answer 22

• Homologous pairs line up on the equator randomly
• Once they separate in the 1st meiosis division it is completely random which chromosome from each pair ends up in which daughter cell
• The same happens in the second meiosis division

Question 23

How does independent segregation increase genetic variation

Answer 23

at the end of meiosis there are different combinations of parental chromosomes in the 4 daughter cells

Question 24

Compare and contrast mitosis and meiosis in terms of number of divisions

Answer 24

Mitosis has one division whereas meiosis has a total of 2 divisions

Question 25

Compare and contrast mitosis and meiosis in terms of number of daughter cells produced

Answer 25

In mitosis 2 daughter cells are produced whereas in meiosis 4 daughter cells are produced

Question 26

Compare and contrast mitosis and meiosis in terms of whether daughter cells are haploid or diploid

Answer 26

Mitosis results in diploid daughter cells whereas meiosis results in haploid daughter cells

Question 27

Compare and contrast mitosis and meiosis in terms of whether daughter cells are genetically identical or different

Answer 27

In mitosis genetically identical daughter cells are produced whereas in meiosis genetically different daughter cells are produced

Question 28

Compare and contrast mitosis and meiosis in terms of whether chromosomes cross over

Answer 28

In mitosis crossing over does not occur whereas in meiosis crossing over of chromosomes does occur

Question 29

What is chromosome non-disjunction

Answer 29

- A type of chromosome mutation - Homologous pairs do not separate in meiosis - Gamete has 2 copies of a chromosome instead of 4 - Fertilisation leads to cells having 3 copies of a particular chromosome

Question 30

What are the possible consequences of a non-disjunction event in organisms

Answer 30

Can lead to inherited conditions because there are the wrong number of chromosomes in the resulting gametes such as Down’s syndrome

Question 31

How do you calculate number of possible chromosome combinations following meiosis

Answer 31

2^n

Question 32

How do you calculate number of posssible chromosome combinations following random fertilisation

Answer 32

(2^n)^2