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Biology OCR > Cell Division Diversity And Organisation > Flashcards

Cell Division Diversity And Organisation Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What’s a gene mutation

A

A change in the base sequence of chromosomes

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2
Q

Why do gene mutations occur

A

Proof reading errors where they mistakenly add or remove a base

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3
Q

What’s a point mutation

A

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

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4
Q

What are base pair deletions

A

One or more bases being incorrectly deleted from the sequence

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5
Q

What’s a base pair substitution

A

One or more bases being incorrectly replaced with another base

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6
Q

What is base pair insertion/addition

A

One or more bases are incorrectly added to the sequence

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7
Q

What are frameshift mutations

A

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

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8
Q

What are sense and non sense mutations (substitutions)

A

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

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9
Q

What’s a sense mutation

A

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

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10
Q

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

A

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

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11
Q

What are non sense mutations

A

A stop codon is coded for producing a shortened protein

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12
Q

Why are non sense mutations so severe

A

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

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13
Q

What are some beneficial aspects of mutations

A

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

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14
Q

What are mutagenic agents

A

They increase the rate of gene mutations

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15
Q

What are some examples of mutagenic agents

A

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

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16
Q

What are chromosomal mutations

A

Mutations that occur in entire chromosomes

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17
Q

Why do chromosomal mutations occur

A

Improper separation of chromosomes during division or improper chromosome recombination

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18
Q

What can breakage of chromosomes result in

A

Deletion, translocation, inversion, duplication

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19
Q

What is deletion

A

When an entire region of a chromosome is accidentally deleted

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20
Q

What is translocation

A

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

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21
Q

What’s inversion

A

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

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22
Q

What is duplication

A

When regions in a chromosome become duplicated

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23
Q

What are the sources of genetic diversity in meiosis

A

Crossing over and independent assortment

24
Q

What is crossing over

A

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

25
Q

What do homologous chromosomes come together to from

A

Bivalents

26
Q

How do chiasmata form

A

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

27
Q

What happens with recombination occurs

A

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

28
Q

What is independent assortment

A

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

29
Q

What happens in meiosis II

A

Each pair of homologous chromosomes is split up

30
Q

How can you measure genetic diversity resulting from meiosis

A

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)

31
Q

An example of measuring genetic diversity from meiosis

A

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

32
Q

What are the differences between mitosis and meiosis

A

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

33
Q

Why is meiosis important for producing variation

A

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

34
Q

What are the two phases of interphase in meiosis

A

S phase
Growth phase (G1+G2)

35
Q

What’s the S phase

A

DNA replication

36
Q

What’s the growth phase G1+G2

A

New proteins and organelles are made

37
Q

What does meiosis I result in

A

2 diploid daughter cells

38
Q

What does meiosis II result in

A

Four haploid cells each with a single copy of every chromosome

39
Q

What’s the difference between meiosis I and meiosis II

A

Meiosis I produces 2 daughter cells whereas meiosis II produces 4

40
Q

What is meiosis

A

The process of cell division which gives rise to gametes

41
Q

Why is meiosis important

A

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

42
Q

What are the benefits of having genetically diverse offspring’s

A

Increases the chances of survival in changing environments

43
Q

How does meiosis help prevent genetic disorders

A

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

44
Q

What does the xylem tissue enable a plant to do

A

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

45
Q

Where are the xylem and phloem located

A

In vascular bundles

46
Q

What are vascular bundles

A

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

47
Q

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

A

To ensure the plant can withstand various mechanical forces

48
Q

Why is the x shaped arrangement surrounded by an endodermis

A

So the xylem vessels are supplied with water

49
Q

What are the inner layer of xylem cells

A

The meristem (pericycle)

50
Q

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

A

They provide support and flexibility

51
Q

What’s the cambium

A

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

52
Q

What do vascular bundles in the leaf form

A

The midrib and veins

53
Q

What do monocotyledonous and dicotyledonous leaves aid in

A

The process of transport and support of xylem and phloem tissue

54
Q

What are xylem cells made up of

A

Dead cells with no end walls so a continuous tube forms

55
Q

Why do xylem vessels have pits

A

To allow water to move sideways between the vessels

56
Q

What is lignin

A

A substance that thickens the vessels

57
Q

Why is lignin deposited in a spiral shape

A

To allow the vessels to remain flexible

Biology OCR (12 decks)

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