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AQA AS Biology > Genetic Diversity, Mutation and Meiosis > Flashcards

Genetic Diversity, Mutation and Meiosis Flashcards

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1
Q

What happens to the number of chromosomes in late interphase?

A

DNA has replicated so it doubles

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2
Q

What is a homologous pair?

A

Two chromosomes, one from each parent, which have the same gene but different alleles

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3
Q

If chromosomes were visible in early interphase, how would they look?

A

They would have only one chromatid

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4
Q

If chromosomes were visible in late interphase how would they look?

A

They would each have two genetically identical chromatids joined by a centromere

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5
Q

What is a gamete?

A

A haploid sex cell

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6
Q

What is haploid?

A

(n) a cell with a single set of unpaired chromosomes (one of each homologous pair)

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7
Q

What is diploid?

A

(2n) A cell with two complete sets of chromosomes (both homologous pairs, one from each parent)

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8
Q

What is fertilisation?

A

Fusion of two haploid gametes to form a zygote

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9
Q

What happens in meiosis?

A
  • Cell division to form gametes- 4 daughter cells- 2 divisions- All daughter cells are genetically different because of independent segregation and crossing over
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10
Q

What happens in mitosis?

A
  • Cell division for growth and repair- 1 division- 2 genetically identical daughter cells
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11
Q

What happens in Prophase 1

A
  • One 4n cell- Chromosomes condense- Nuclear membrane breaks down
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12
Q

What happens in Metaphase 1

A
  • One 4n- Homologous pairs line up - Spindle forms and attaches to the centromeres
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13
Q

What happens in Anaphase 1

A
  • One 4n- Homologous pairs are separated - Pulled apart to opposite poles
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14
Q

What happens in Telophase 1

A
  • Two 2n cells- Nuclei reform- Cell divides
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15
Q

What happens in Prophase 2

A
  • Two 2n cells- Nuclear membrane breaks down
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16
Q

What happens in Metaphase 2

A
  • Two 2n cells- Chromosomes line up on the equator- Spindle forms and attaches to centromeres
17
Q

What happens in Anaphase 2

A
  • Two 2n cells- Chromatids are separated and pulled apart to opposite poles
18
Q

What happens in Telophase 2

A
  • Four n cells- Nuclear membrane reforms - Cell divides
19
Q

What is crossing over?

A

A different combination of alleles

20
Q

When does crossing over take place?

A

During metaphase 1

21
Q

What happens during crossing over?

A

Chromatids of homologous pairs cross over and swap alleles

22
Q

What is independent segregation?

A

Different combinations of chromosomes, the homologous pairs can line up in two different ways which will lead to genetic variation

23
Q

What is a gene mutation?

A

A change to the base sequence of DNA during DNA replication

24
Q

What is a base substitution?

A

Swapping one base for a different base that may/may not code for the same amino acid

25
Q

What is a base deletion?

A

One base is removed causing a frame shift and therefore changing all of the following triplets/codons

26
Q

How can mutations cause a non-functional protein?

A

A change to the DNA code (deletion or substitution) causes a change in the mRNA codon and therefore the tRNA anticodon and a different amino acid will be added to the primary protein structure. Due to a change in the primary protein structure, bonding and folding in the secondary and tertiary protein structure will change and therefore the proteins specific shape will be changed so the protein can no longer carry out is function

27
Q

How can mutations cause a still functional protein?

A

Due to DNA being degenerate each amino acid can be coded for by multiple triplet codes therefore a substitution may have no effect on the primary structure so there will be no effect on the bonding in the tertiary structure so shape will remain the same and the protein will be functional

28
Q

What is a chromosome non-disjunction?

A

When chromosomes dont separate properly

29
Q

When can chromosome non-disjunction take place?

A

Meiosis 1 and Meiosis 2

30
Q

What does a chromosome non-disjunction cause?

A

An uneven number of chromosomes in the gametes and therefore genetic diseases such as down syndrome

31
Q

Within a human haploid cell, how many chromosomes are there?

A

23

32
Q

When a sperm and an egg fuse together, what is the cell it forms called?

A

Zygote

33
Q

By the end of meiosis, how many resulting cells are there?

A

4

34
Q

Which substitutions does not end up coding for a different amino acid?

A

Silent

35
Q

3 things that can be formed from meiosis

A

Sperm, Egg, Pollen

36
Q

What is the name for when the base sequence is changed within a DNA molecule?

A

Mutation

37
Q

Genetic diversity is ensured by meiosis in which way?

A

Independent segregation and crossing over

38
Q

At which point in DNA will a deletion mutation have the least effect?

A

No difference where, even at the end it will effect the stop codon

AQA AS Biology (18 decks)

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