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A-Level Biology > Genetic Information And Reltionships - Meiosis And Mutation > Flashcards

Genetic Information And Reltionships - Meiosis And Mutation Flashcards

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1
Q

Chromosome definition

A

An independent DNA molecule

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2
Q

Gene definition

A

A base sequence of DNA that codes for a polypeptide or functional RNA

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3
Q

Allele definition

A

Different forms of the same gene

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4
Q

Locus definition

A

The fixed position of a gene on a particular chromosome

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5
Q

Homologous chromosomes definition

A

A pair of chromosomes which have the same genes at thee same gene loci but may have different alleles

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6
Q

Haploid cell definition

A

A cell containing one of each type of chromosome (n) e.g. a gamete

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7
Q

Diploid cell definition

A

A cell containing two of each type of chromosome as pairs (2n) e.g normal body cell

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8
Q

(N) meaning

A

The number of types of chromosomes in a cell

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9
Q

(2n) meaning

A

The total number of chromosomes in a diploid cell

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10
Q

What is a mutation

A

A change in the sequence of DNA bases

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11
Q

How does a mutation arise

A

Mutations can arise spontaneously during DNA replication and and include base deletion and base substitution

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12
Q

What is a substitution mutation

A

One base is swapped with another different base

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13
Q

What is a deletion mutation

A

One base is removed from the sequence

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14
Q

What are the possible effects of a substitution mutation on a protein

A

Sometimes none because of the degenerate nature of the genetic code

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15
Q

What is the effect of a deletion mutation on a protein

A

There is always an effect because the election of a base will cause a frame shift in all the base triplets after it

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16
Q

Name some possible mutagenic agents

A

Ionising radiation, UV radiation, some viruses, some chemicals

17
Q

What is the role of mutagenic agents

A

Mutgenic agents increase the rate of chance of mutations

18
Q

What happens during crossing over

A
  • Homologous chromosomes come together as a pair formimg a bivalent
  • Non-sister chromatids cross over
  • The point of the cross is called chiasmata
  • Getenic information is swapped
19
Q

How does crossing over increase genetic variation

A

The resulting chromatids after crossing over contain the same genes but have a different combination of alleles

20
Q

What is crossing over

A

The swapping of genetic information between homologous pairs of chromosomes

21
Q

What is independent segregation

A

The random positioning of homologous pairs

22
Q

What happens during independent segregation

A
  • Homologous pairs line up on the equator randomly
  • Once they separate in the 1st meiosis division it is completely random which chromosome from each pair ends up in which daughter cell
  • The same happens in the second meiosis division
23
Q

How does independent segregation increase genetic variation

A

at the end of meiosis there are different combinations of parental chromosomes in the 4 daughter cells

24
Q

Compare and contrast mitosis and meiosis in terms of number of divisions

A

Mitosis has one division whereas meiosis has a total of 2 divisions

25
Q

Compare and contrast mitosis and meiosis in terms of number of daughter cells produced

A

In mitosis 2 daughter cells are produced whereas in meiosis 4 daughter cells are produced

26
Q

Compare and contrast mitosis and meiosis in terms of whether daughter cells are haploid or diploid

A

Mitosis results in diploid daughter cells whereas meiosis results in haploid daughter cells

27
Q

Compare and contrast mitosis and meiosis in terms of whether daughter cells are genetically identical or different

A

In mitosis genetically identical daughter cells are produced whereas in meiosis genetically different daughter cells are produced

28
Q

Compare and contrast mitosis and meiosis in terms of whether chromosomes cross over

A

In mitosis crossing over does not occur whereas in meiosis crossing over of chromosomes does occur

29
Q

What is chromosome non-disjunction

A
  • A type of chromosome mutation
  • Homologous pairs do not separate in meiosis
  • Gamete has 2 copies of a chromosome instead of 4
  • Fertilisation leads to cells having 3 copies of a particular chromosome
30
Q

What are the possible consequences of a non-disjunction event in organisms

A

Can lead to inherited conditions because there are the wrong number of chromosomes in the resulting gametes such as Down’s syndrome

31
Q

How do you calculate number of possible chromosome combinations following meiosis

A

2^n

32
Q

How do you calculate number of posssible chromosome combinations following random fertilisation

A

(2^n)^2

A-Level Biology (23 decks)

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