Cell Division Diversity And Organisation

Question 1

What’s a gene mutation

Answer 1

A change in the base sequence of chromosomes

Question 2

Why do gene mutations occur

Answer 2

Proof reading errors where they mistakenly add or remove a base

Question 3

What’s a point mutation

Answer 3

Mutations in a single base of DNA or a gain of a single incorrect base

Question 4

What are base pair deletions

Answer 4

One or more bases being incorrectly deleted from the sequence

Question 5

What’s a base pair substitution

Answer 5

One or more bases being incorrectly replaced with another base

Question 6

What is base pair insertion/addition

Answer 6

One or more bases are incorrectly added to the sequence

Question 7

What are frameshift mutations

Answer 7

Adding/removing a base from a sequence cause the bases to move up/down changing how the gene is read

Question 8

What are sense and non sense mutations (substitutions)

Answer 8

Affects a sequence of a single codon, the rest of the sequence remains unaffected

Question 9

What’s a sense mutation

Answer 9

A codon changing but an amino acid is still produced, the amino acid can be the same or different

Question 10

Why may mutations in the third base of a codon have little effect

Answer 10

The third base of a codon usually doesn’t change the amino acid due to the degenerate nature of codons

Question 11

What are non sense mutations

Answer 11

A stop codon is coded for producing a shortened protein

Question 12

Why are non sense mutations so severe

Answer 12

They can result in a dysfunctional proteins which can have adverse effects on cells or be lethal

Question 13

What are some beneficial aspects of mutations

Answer 13

They can lead to the development of new alleles which can contribute to genetic diversity in a gene pool, and help natural selection

Question 14

What are mutagenic agents

Answer 14

They increase the rate of gene mutations

Question 15

What are some examples of mutagenic agents

Answer 15

Ionising radiation (x-rays and gamma rays)
HPV, Formaldehyde and benzene

Question 16

What are chromosomal mutations

Answer 16

Mutations that occur in entire chromosomes

Question 17

Why do chromosomal mutations occur

Answer 17

Improper separation of chromosomes during division or improper chromosome recombination

Question 18

What can breakage of chromosomes result in

Answer 18

Deletion, translocation, inversion, duplication

Question 19

What is deletion

Answer 19

When an entire region of a chromosome is accidentally deleted

Question 20

What is translocation

Answer 20

When a portion of one chromosome is accidentally switched with a separate non homologous chromosome

Question 21

What’s inversion

Answer 21

When a portion of a chromosome can break and rejoin into the original chromosome but after inverting itself resulting in a change in sequence

Question 22

What is duplication

Answer 22

When regions in a chromosome become duplicated

Question 23

What are the sources of genetic diversity in meiosis

Answer 23

Crossing over and independent assortment

Question 24

What is crossing over

Answer 24

When two homologous chromosomes come together and align and then recombine and swap parts with each other

Question 25

What do homologous chromosomes come together to from

Answer 25

Bivalents

Question 26

How do chiasmata form

Answer 26

Non sister chromatids wrap around each other joining up at certain points

Question 27

What happens with recombination occurs

Answer 27

The chromatids still have the same genes but may have different alleles

Question 28

What is independent assortment

Answer 28

Each chromosome is inherited randomly and independently of other chromosomes (one chromosome does not effect the inheritance of another)

Question 29

What happens in meiosis II

Answer 29

Each pair of homologous chromosomes is split up

Question 30

How can you measure genetic diversity resulting from meiosis

Answer 30

n= number of homologous pairs (Due to splitting in meiosis combos of chromosomes in gametes are 2n, due to independent assortment each chromosome can undergo further randomisation (2n)2)

Question 31

An example of measuring genetic diversity from meiosis

Answer 31

Humans have 23 pairs of chromosomes (n=23) 2n=46 (2n)2=2116 2116 different possible combos of chromosomes which can be inherited

Question 32

What are the differences between mitosis and meiosis

Answer 32

Mitosis: 2 daughter cells, genetically identical daughter cells, daughter cells genetically identical to parent cell, daughter cells are diploid, stages: prophase I metaphase I anaphase I Telophase I, no crossing over, homologous pairs not separated Meiosis: 4 daughter cells, genetically different daughter cells, daughter cells genetically different to parent cell, crossing over yes, homologous pairs separated in anaphase II, stages: prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II, telophase II

Question 33

Why is meiosis important for producing variation

Answer 33

It shuffles genetic material in a way that leads to formation of new combinations of alleles

Question 34

What are the two phases of interphase in meiosis

Answer 34

S phase Growth phase (G1+G2)

Question 35

What’s the S phase

Answer 35

DNA replication

Question 36

What’s the growth phase G1+G2

Answer 36

New proteins and organelles are made

Question 37

What does meiosis I result in

Answer 37

2 diploid daughter cells

Question 38

What does meiosis II result in

Answer 38

Four haploid cells each with a single copy of every chromosome

Question 39

What’s the difference between meiosis I and meiosis II

Answer 39

Meiosis I produces 2 daughter cells whereas meiosis II produces 4

Question 40

What is meiosis

Answer 40

The process of cell division which gives rise to gametes

Question 41

Why is meiosis important

Answer 41

Required for sexual reproduction, there’s no sex cells without mitosis (ensures cells are haploid) Meiosis produces genetic diversity as the 4 daughter cells aren’t identical

Question 42

What are the benefits of having genetically diverse offspring’s

Answer 42

Increases the chances of survival in changing environments

Question 43

How does meiosis help prevent genetic disorders

Answer 43

Ensures genetic material is divided + distributed accurately avoiding errors Crossing over can repair damaged DNA

Question 44

What does the xylem tissue enable a plant to do

Answer 44

Enables water and dissolved minerals to travel up the plant in the passive process of transpiration

Question 45

Where are the xylem and phloem located

Answer 45

In vascular bundles

Question 46

What are vascular bundles

Answer 46

Strands of vascular tissue containing the xylem and phloem vessels that distribute water and organic substances around the plant and serve as structural support

Question 47

Why is there an x shaped arrangement in the centre of vascular bundles

Answer 47

To ensure the plant can withstand various mechanical forces

Question 48

Why is the x shaped arrangement surrounded by an endodermis

Answer 48

So the xylem vessels are supplied with water

Question 49

What are the inner layer of xylem cells

Answer 49

The meristem (pericycle)

Question 50

Why is the placement of the xylem cell beneficial in non wooden plants

Answer 50

They provide support and flexibility

Question 51

What’s the cambium

Answer 51

Meristem cells which aid the production of new xylem and phloem tissue

Question 52

What do vascular bundles in the leaf form

Answer 52

The midrib and veins

Question 53

What do monocotyledonous and dicotyledonous leaves aid in

Answer 53

The process of transport and support of xylem and phloem tissue

Question 54

What are xylem cells made up of

Answer 54

Dead cells with no end walls so a continuous tube forms

Question 55

Why do xylem vessels have pits

Answer 55

To allow water to move sideways between the vessels

Question 56

What is lignin

Answer 56

A substance that thickens the vessels

Question 57

Why is lignin deposited in a spiral shape

Answer 57

To allow the vessels to remain flexible