3.4.2 Genetic Diversity Flashcards

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1
Q

How can a gene mutation result in a protein not being synthesised?

A

Mutation changes sequence of bases, A premature stop codon or frame shift is changed by the mutation. Transcription/translation does not occur

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2
Q

What are gametes?

A

The male and female sex cells found in all organisms that reproduce sexually

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3
Q

Why is it important that gametes only have one set of chromosomes ?

A

So that the diploid number of chromosomes can be restored after fertilisation

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4
Q

Describe a haploid nucleus

A

One set of chromosomes, half the number of chromosomes found in a normal body cell. Contains one chromosome from each homologous pair, type of nucleus found in gametes

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5
Q

Describe a diploid nucleus

A

Two sets of chromosomes

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6
Q

Describe meiosis

A

Type of cell division that produces gametes, 4 haploid daughter cells are produced

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7
Q

Define genetic variation

A

Differences that exist between individual’s genetic material

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8
Q

How does meiosis produce cells that are genetically different ?

A

Through crossing over of chromatids and independent assortment of chromosomes

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9
Q

Explain the crossing over process

A

During first division in meiosis, the homologous pairs of chromosomes come together and pair up. Two of the chromatids in each homologous pair twist around each other. the twisted bits break off their original chromatid and rejoin on the other chromatid, recombining their genetic material, exchanging sections of DNA.

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10
Q

How does crossing over increase genetic variation ?

A

Each four new cells formed from meiosis contains chromatids with different combinations of alleles

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11
Q

Describe independent assortment

A

The random distribution of different chromosomes in the gametes. When gametes are produced, different combinations of the maternal and paternal chromosomes go into each cell. Only one chromosome from each pair ends up in each gamete

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12
Q

Explain the importance of meiosis in gametes production

A

To half the chromosome number producing a haploid nucleus, so at fertilisation the diploid number of chromosomes is restored. It allows genetic variation through independent assortment and crossing over.

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13
Q

Why does asexual reproduction lead to low genetic diversity ?

A

Low genetic diversity means there are few different alleles in the gene pool. Asexual reproduction leads to all offspring being genetically identical. No meiosis.

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14
Q

What is a mutation?

A

Change to the base sequence of DNA. Caused by errors during DNA replication

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15
Q

What is a substitution mutation?

A

When one base is substituted with another

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16
Q

What is a deletion mutation?

A

When one base is deleted

17
Q

What is an insertion mutation?

A

When an extra base is added

18
Q

What is an duplication mutation?

A

Duplication - one or more bases are repeated

19
Q

What is a point mutation?

A

Point mutation - a change in a single nucleotide

20
Q

What is a frame shift mutation?

A

Frame shift mutation - the reading frame changes and this results in a different protein structure

21
Q

What’s the difference between a DNA mutation and a chromosome mutation?

A

Mutation = change in the DNA. Chromosome mutation = changes in the structyre or number of whole chromosomes. E.g. an organism having an extra chromosome

22
Q

Define ‘allele frequency’

A

The frequency of a particular allele in a gene pool

23
Q

Distinguish between stabilising selection and directional selection

A

Directional selection causes changes in the allele frequency so the norm curve shifts in one direction. Stabilising selection favours the organisms closest to the mean and selects against those at the extremes so the norm curve becomes ‘squashed’

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25
Q
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