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Biology- Porteous > 3.4.3 Gentic Diversity can arise as a result of mutation or during meiosis > Flashcards

3.4.3 Gentic Diversity can arise as a result of mutation or during meiosis Flashcards

1
Q

Define mutation.

A

Any change to the DNA of an organism

Either the quantity of DNA or the base sequence

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2
Q

When do most mutations occur?

A

DNA replication

Cell division

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3
Q

Define gene mutation.

A

A change in the base sequence of the DNA of an organism

Arise through mistake in DNA replication

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4
Q

Define chromosome mutation.

A

A change in the number or structure of whole chromosomes

Arise during cell division

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5
Q

If mutation occurs in a body cell will it be passed onto the offspring of that individual?

A

No
Only passed on from faulty gametes
In which case all the offsprings cells would mutate

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6
Q

When does mutation of gametes occur?

A

Meiosis

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7
Q

How does a change in base sequence effect the protein made?

A

Causes change in mRNA base sequence
Changes amino acid sequence
This causes changes in potentially any bond
This changes the tertiary structure of the proteins
It is entirely different now

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8
Q

Define substitution mutation.

A

Where a nucleotide in a DNA molecule is replaced by another nucleotide that has a different base

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9
Q

Define addition mutation.

A

The insertion of an extra base

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10
Q

Define deletion mutation.

A

The removal of one base

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11
Q

Define duplication mutation. (not on spec)

A

Addition of a complete codon

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12
Q

Define inversion mutation. (not on spec)

A

Where the code is read backwards

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13
Q

Define frame shift.

A

Where all subsequent codons are altered

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14
Q

When does frame shift have the biggest effect?

A

The close to the start of a gene it occurs

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15
Q

Define non-sense mutation.

A

Results in a stop codon

Poly-peptide production stops prematurely

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16
Q

What is a mis-sense mutation?

A

Different amino acid is coded for

Effect is dependant of the function of the amino acid

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17
Q

How would a mis-sense mutation effect an enzymes function?

A

The active site would no longer be complementary

Can’t form enzyme-substrate complexes

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18
Q

What is a silent mutation?

A

The substitutes base still codes for the same amino acid

No effect

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19
Q

Name some key causes of mutations?

A 
Ionising radiation
Inherited genetic disorders
Random
Increased likelihood with age
Carcinogens (tar in cigs)
Alcohol
Infections (HVB)
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20
Q

What is product of meiosis?

A

4 genetically variable daughter cells

21
Q

Simply describe meiosis.

A

Parent cell (diploid)
DNA replicates
Homologous pairs separate (meiosis 1)
Chromatids separate to form 4 daughter cells
Each contains half the number of chromosomes of the parent cell

22
Q

How many chromosomes does a daughter cell of meiosis contain?

A

Half that of the parent

23
Q

What must occur in the parent cell before meiosis 1 can occur?

A

DNA replication

24
Q

Why is it important that the chromosome number is halved in meiosis?

A

The diploid number is restored at fertilisation

If gametes weren’t haploid, the chromosome number would double with each new generation

25
Q

List all the ways in which meiosis and sexual reproduction lead to variation.

A

Crossing over
Independent segregation of homologous chromosomes
Independent segregation of chromatids
Random fusion of gametes (only sexual reproduction)

26
Q

What process could cause blocks of genes to swap between chromosomes?

A

Crossing over

27
Q

What stage of meiosis does crossing over take place in?

A

Metaphase of meiosis 1

28
Q

Explain how crossing over occurs?

A

Homologous chromosomes line up on the equator in metaphase of meiosis 1
They sometimes get tangled
The chromosomes are pulled apart in anaphase of meiosis 1
Blocks of genes may get swapped between chromosomes

29
Q

What are the basic stages that meiosis and mitosis share?

A

Doubling of DNA
Assembly in centre of cell
Separation of chromosomes
Cell division

30
Q

How many divisions occur in meiosis?

A

2

31
Q

How many divisions occur in mitosis?

A

1

32
Q

How many daughter cells are produced in meiosis?

A

4

33
Q

How many daughter cells are produced by mitosis?

A

2

34
Q

Is there variation in the daughter cells produced by meiosis?

A

Yes
Genetically variable
Daughters have half the number of chromosomes (haploid)

35
Q

Is there variation in the daughter cells produced by mitosis?

A

No
Genetically identical
Full set of chromosomes (diploid)

36
Q

List the phases of Meiosis.

A 
Interphase 1
Prophase 1
Metaphase 1
Anaphase 1
Telophase and cytokinesis
Prophase 2 
Metaphase 2
Anaphase 2
Telophase 2
37
Q

What occurs in interphase 1?

A

Growth
Synthesis of organelles
DNA replication

38
Q

What occurs in prophase 1?

A 
Condensing chromosomes
Homologous pairs forming
Crossing over
Nuclear membrane disintegrates
Spindle formation
39
Q

What happens at metaphase 1?

A

Homologous chromosomes line up on the equator
Spindle fibres starch to each centromere
Independent assortment

40
Q

What happens in anaphase 1?

A 
Spindle fibres contract (which leads to..)
Separation of homologous chromosomes
2 sister chromatids
Independent segregation 
Chromosome number halved
41
Q

What happens at telophase 1?

A

Half the number of chromosomes at each pole
Sometimes chromosomes unravel
2 haploid daughter cells

42
Q

What happens at prophase 2?

A

Spindle fibres form

Cell membrane disintegrates

43
Q

What happens at metaphase 2?

A

Chromosomes line up on equator

Spindle fibres join at the equator

44
Q

What happens at anaphase 2?

A

Spindle fibres contract at the poles

Sister chromatids move towards poles

45
Q

What happens at telophase 2?

A

4 daughter cells containing two chromatids

46
Q

What does non-disjunction mean?

A

The failure of chromatids to separate at anaphase of meiosis 2
Results in one too many/one too few chromosomes

47
Q

What condition would having an extra chromosome 21 result in?

A

Down’s syndrome

48
Q

What is a tetrad?

A

Two homologous chromosomes together

Biology- Porteous (14 decks)

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