4.3 Flashcards

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1
Q

gene mutation

A

change in dna base sequence
can arise spontaneously during dna replication

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2
Q

mutagenic agent

A

increase rate of gene mutation eg uv

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3
Q

Mutation leading to non functional protiens

A

Change sequence of base triplets I’m dna so changes sequence codons in mRNA
Change AA seq in polypeptides
Change position of bonds
Changes tertiary structure
Enzyme active site changes shape So substrate can’t bind so ES can’t form

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4
Q

Substitution effects

A

Base in dna replaced by another base
Change some triplet so changes one mRNA codon
So one AA in polypeptide changes
Tertiary structure may change if bond position changes
Or AA doesn’t change as degenerate or mutation in introns

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5
Q

Deletion mutation

A

One base removed from DNA sequence
Change sequence of dna triplets from point of mutation
Changes sequence of mRNA codons after point of mutation
So AA seq in primary structure of polypeptide changes
Bond position changes so tertiary structure and shape of protein changes

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6
Q

Homologous chromosome features

A

Same length and same genes but different alleles

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7
Q

Diploid

A

2 complete sets of chromosomes 2N

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8
Q

Haploid

A

Single set of unpaired chromosomes represented as n

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9
Q

Cell division by meiosis

A

Meiosis 1 separates homologous chromosome chromosomes sp chromosomes arrange into homologous pairs
Crossing over and independent segregation
Meiosis 2 separates chromatids

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10
Q

How does crossing over create genetic variation

A

Homologous pairs of chromosomes form bivalent
Chiasmata form
Alelles exchanged between chromosomes
Create new combo of maternal paternal alleles on chromosome

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11
Q

Independent segregation and genetic variation

A

Homologous pairs randomly align at equator so random which chromosome from each pair goes to daughter cell
Creates dif combos of maternal and paternal alleles on chromosomes

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12
Q

What else causes genetic variation

A

Random fertilisation

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13
Q

Mitosis vs meiosis

A

Mitosis 2 daughter cells but meiosis 4 as 2 divisions
Mitosis genetically identical but meiosis genetically varied as crossing over and independent segregation
Mitosis maintains chromosome number but meiosis halves chromosomes number

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14
Q

Importance of meiosis

A

2 division create haploid gametes halving the number of chromosomes
So diploid number is restored at fertilisation so chromosome number maintained between generations
Independent segregation and crossing over creates genetic variation

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15
Q

How can you recognise where meiosis and mitosis occur in a life cycle?

A

Mitosis occurs between stages where chromosome number is maintained
Meiosis occurs between stages where chromosome number halves

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16
Q

Describe how mutations in the number of chromosomes arise

A

● Spontaneously by chromosome non-disjunction during meiosis
● Homologous chromosomes (meiosis I) or sister chromatids (meiosis II) fail to separate during meiosis
● So some gametes have an extra copy (n+1) of a particular chromosome and others have none (n-1)