3.4.4 MUTATIONS + MEIOSIS

Question 1

Gene mutations involve…

Answer 1

a change in the base sequence of chromosomes

Question 2

Gene mutations can arise..

Answer 2

Spontaneously

Question 3

Gene mutations occur during…

Answer 3

DNA replication and can involve deletion and substitution

Question 4

Due to the ………. nature of the genetic code, not all base ………… cause a change in the sequence of amino acids:

Answer 4

• degenerate
• substitutions

Question 5

What increase the rate of a gene mutation?

Answer 5

Mutagenic agents

Question 6

How do mutations in chromosomes occur?

Answer 6

• spontaneously
• by chromosome non- disjunction
• during meiosis

Question 7

Materials which may increase the risk of a mutation:

Answer 7

• ultraviolet/ ionising radiation
• chemicals
• viruses

Question 8

What happens in substitution?

Answer 8

One base is replaced by another

Question 9

What happens in deletion?

Answer 9

One base is removed from the sequence

Question 10

What happens in insertion?

Answer 10

One base is added into the sequence

Question 11

Will substitution result in a change to the amino acid sequence of a protein?

Answer 11

Not always- may still code for the same amino acid

Question 12

Will deletion result in a change to the amino acid sequence?

Answer 12

Yes, they are more likely to change the amino acid sequence because they cause a frame shift- this changes all the triplets after the deletion and so also changes the amino acid sequence

Question 13

Will insertion cause a change to the amino acid sequence?

Answer 13

More likely to because they cause a frame shift

Question 14

What is a polyploidy chromosome mutation?

Answer 14

When organisms have more than two sets of chromosomes- mostly seen in plants

Question 15

How many daughter cells does meiosis produce?

Answer 15

4

Question 16

Are the daughter cells from meiosis genetically different or the same as one another?

Answer 16

Different

Question 17

Are the daughter cells produced in meiosis haploid or diploid?

Answer 17

Haploid

Question 18

How many divisions occur in meiosis?

Answer 18

2

Question 19

What are genetically different daughter cells a result of in meiosis?

Answer 19

Independent segregation of homogolous chromosomes

Question 20

Crossing over of homologous chromosomes results in…

Answer 20

Further genetic variation among daughter cells

Question 21

What is independent segregation of homologous chromosomes?

Answer 21

During meiosis I, each chromosome lines up alongside its homologous partner randomly, since the pairs line up randomly, the combination of chromosomes of maternal and paternal origin that go into the daughter cell at meiosis I is also a matter of chance

Question 22

Variety from new genetic combinations:

Answer 22

Each member of a homologous pair of chromosomes has exactly the same genes and therefore determines the same characteristics (tongue rolling), however the alleles of these genes may differ (they may code for rollers or non rollers), the independent assortment of these chromosomes may produce new, genetic combinations

Question 23

What is a gene?

Answer 23

A length of DNA that codes for a polypeptide

Question 24

What is an allele?

Answer 24

One of the different forms of a particular gene

Question 25

What is a locus?

Answer 25

The position of a gene on a chromosome or DNA molecule

Question 26

What are homologous chromosomes?

Answer 26

A pair of chromosomes, one maternal and one paternal, that have the same gene loci

Question 27

Genetic recombination by crossing over:

Answer 27

- during meiosis 1, each chromosome lines up alongside its homologous partner randomly, the following then takes place: * the chromatids of each pair become twisted around one another * during this twisting process tensions are created and portions of the chromatids break off * these broken portions might then rejoin with the chromatids of its homologous partner * usually it is the equivalent portions of homologous chromosomes that are exchanged * in this way new genetic combinations of maternal and paternal alleles are produced

Question 28

The chromatids cross over one another many times..

Answer 28

Process known as crossing over

Question 29

What is recombination?

Answer 29

- broad term which refers to the exchange of genetic material between different molecules of DNA - results in new combinations of genetic information - can occur during meiosis and mitosis

Question 30

What kind of division is meiosis?

Answer 30

Reduction- diploid to haploid

Question 31

What happens before meiosis starts?

Answer 31

DNA is replicated during interphase so that each chromosome contains two chromatids

Question 32

2n =

Answer 32

Diploid

Question 33

N=

Answer 33

Haploid

Question 34

What happens in meiosis 1?

Answer 34

Homologous chromosomes are separated

Question 35

What happens in meiosis 11?

Answer 35

Chromatids are separated

Question 36

What happens in prophase 1?

Answer 36

- chromosomes condense and homologous chromosomes pair up - centrioles migrate to opposite poles of the cell where they each start to form spindle fibres - the nucleolus disappears and the nuclear envelope starts to break down, leaving chromosomes free in the cytoplasm

Question 37

What happens in metaphase 1?

Answer 37

- chromosomes line up along the equator of the cells in their homologous pairs - each chromosome attaches to the spindle by their centromere

Question 38

What happens in anaphase 1?

Answer 38

- homologous chromosome pairs are separated and pulled to opposite poles of the cell by spindle fibres - chromatids stay joined together

Question 39

What happens in telophase 1?

Answer 39

- the chromosomes reach opposite poles of the cell where they uncoil - a nuclear envelope firms around each set of chromosomes and the nucleolus starts to reform - the cytoplasm divides to form two cells in cytokenesis

Question 40

What happens in prophase 2?

Answer 40

Same as prophase 1 except chromosomes are now visible under a microscope

Question 41

What happens in metaphase 2?

Answer 41

Same as metaphase 1

Question 42

What happens in anaphase 2?

Answer 42

- centromeres divide and separate each pair of chromatids - spindle fibres contract and shorten to pull the chromatids to opposite poles of the cell

Question 43

What happens in telophase 2?

Answer 43

- the chromatids reach opposite poles of the cell where they uncoil to become long + thin again - a nuclear envelope forms around each set of chromosomes to form two nuclei and the nucleolus starts to reform - cytoplasm divides in cytokenesis - 4 daughter cells produced

Question 44

Function: mitosis vs meiosis

Answer 44

Growth and repair VS production of gametes

Question 45

Type of reproduction: mitosis VS meiosis

Answer 45

Asexual VS sexual

Question 46

Diploid or haploid?: mitosis VS meiosis

Answer 46

Diploid VS haploid

Question 47

Amount of daughter cells: mitosis VS meiosis

Answer 47

2 VS 4

Question 48

Number of cell divisions: mitosis VS meiosis

Answer 48

1 VS 2

Question 49

Creates genetic variation?: mitosis VS meiosis

Answer 49

No VS yes

Question 50

Separates homologous chromosomes?: mitosis VS meiosis

Answer 50

No VS yes in anaphase 1