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Biology > SB3: Genetics > Flashcards

SB3: Genetics Flashcards

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1
Q

What is sexual reproduction?

A

It is a type of reproduction that involves the fusion of gametes. A gamete from each parent fuses to form a zygote. Genetic information from each gamete is mixed so the resulting zygote is unique.

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2
Q

What are gametes?

A

Sex cells (sperm or egg cells). They are haploid, meaning they have half the number of chromosomes (23 chromosomes)

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3
Q

What is meiosis?

A

It is a form of cell division involved in the formation of gametes. The chromosome number is halved and it involves two division (so products are 4 genetically different haploid cells.)

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4
Q

What must happen before in order for meiosis to happen?

A

Interphase

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5
Q

What happens during the first stage of meiosis?

A

Chromosome pairs line up along the cell equator. The pair of chromosomes are separated and move to opposite poles of the cell (the side to which each chromosome is pulled is random, creating variation).

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6
Q

What happens during the second stage of meiosis?

A

Chromosomes line up along the cell equator. The chromatids are separated and move to opposite poles of the cell. Four genetically different haploid cells are produced.

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7
Q

Why is the meiosis important for sexual reproduction? [2 marks]

A

It increases genetic variation. It ensures that the resultant zygote is diploid.

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8
Q

What is the advantage of sexual reproduction?

A

It creates genetic variation, increasing the probability of species adapting to and surviving environmental changes.

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9
Q

Describe the disadvantages of sexual reproduction. [2 marks]

A

Two parents are requires. This makes reproductionn difficult in endangered populations or in species which have a solitary lifestyle. More time and energy is required so fewer offspring are produced.

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10
Q

What is asexual reproduction?

A

Type of reproduction. Involves mitosis. Produces genetically identical offspring.

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11
Q

Describe the advantages of asexual reproduction [3 marks]

A

Only one parent is required. Lots of offspring can be produced in a short period of time, enabling the rapid colonisation of an area and reducing competition from other species. Requires less energy.

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12
Q

What is the disadvantage of asexual reproduction?

A

No genetic variation (except from mutations) reducing the probability of a species being able to adapt to environmental change.

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13
Q

What is DNA?

A

A double-stranded polymer of nucleotides, to form a double helix structure.

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14
Q

What are the monomers of DNA?

A

Nucleotides

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15
Q

What are nucleotides made up of?

A

Common sugar, Phosphate group and one of four bases (A, T, C or G)

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16
Q

What are the full names of the four bases found in nucleotides?

A

Adenine
Thymine
Cytosine
Guanine

17
Q

Describe how nucleotides interact to form a molecule of DNA.

A

Sugar and phosphate molecules join to form a sugar-phosphate backbone in each DNA strand. The bases are connected to each sugar. The complementary base pairs (A with T, C with G) are joined by weak hydrogen bonds.

18
Q

Define genome.

A

The entire genetic material of an organism.

19
Q

What is a chromosome?

A

A long, coiled molecule of DNA that carries genetic information in the form of genes.

20
Q

Define gene.

A

A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation (chemical bonding) to form a protein.

21
Q

Describe the method used to extract DNA from fruit. [6 marks]

A
  1. Place a piece of fruit in a beaker and crush it.
  2. Add detergent and salt, mix.
  3. Filter the mixture and collect the liquid in a test tube.
  4. Pour ice-cold ethanol into the test tube
  5. DNA precipitate forms a white solid
  6. Use a glass rod to collect the DNA sample.
22
Q

Why is detergent added to the crushed fruit?

A

It breaks down the cell membrane releasing the DNA into the solution.

23
Q

Why is salt added to the crushed fruit?

A

Salt precipitates the DNA.

24
Q

Why is ice-cold ethanol added rather than water?

A

DNA is insoluble in ethanol, which makes the DNA visible.

25
Q

Explain how a gene codes for a protein.

A

A sequence of three bases in a gene forms a codon. Each codon codes for one amino acid. The order of amino acids determines the structure and function of protein formed.

26
Q

Why is the ‘folding’ of amino acids important in proteins such as enzymes?

A

The folding of amino acids determines the shape of the active site which must be highly specific to the shape of its substrate.

27
Q

What is protein synthesis?

A

The formation of a protein from a gene.

28
Q

What are the two stages of protein synthesis?

A

Transcription and Translation.

29
Q

What does transcription involve?

A

The formation of mRNA (copy) from a DNA template.

30
Q

Outline the process of transcription.

A

The genome, slide 37

31
Q
A

Biology (3 decks)

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