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Biology Paper 1 > B3- Genetics > Flashcards

B3- Genetics Flashcards

1
Q

What is sexula reproduction?

A
  • A type of reproduction
  • Involves the production of gametes by meiosis
  • A gamete from each parent fuses to from a zygote
    Genetic information from eahc gamete is mixed so the resulting zygote is unique
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2
Q

What is meiosis?

A
  • Form of cell division involved in the information of gamets
  • Chromosone number is halved
    Involves two divisions
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3
Q

What must occur prior to meiosis?

A

Interphase

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4
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)

● Chromosome number is halved

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5
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 unique haploid gametes are produced

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6
Q

Why is meiosis important for sexual reproduction?

A

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

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7
Q

What is the advantage of sexual reproduction?

A

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

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8
Q

Describe the disadvantages of sexual reproduction

A

● Two parents are required. This makes reproduction
difficult in endangered populations or in species which
exhibit solitary lifestyles
● More time and energy is required so fewer offspring
are produced

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9
Q

What is asexual reproduction?

A

● Type of reproduction
● Involves mitosis
● Produces genetically identical offspring
known as daughter cells

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10
Q

Describe the advantages of asexual reproduction

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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11
Q

What is the disadvantage of asexual reproduction?

A

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

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12
Q

What are alleles?

A

Different versions of the same gene

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13
Q

Define genotype

A

An organisms genetic composition, describes all alleles

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14
Q

Define phenotype

A

An organisms observabel characteristics due to interatcions of the genotype and environment

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15
Q

What is homozygous

A

Having two iddenticles alleles of a gene. e.g FF or ff

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16
Q

Define hetrozygous

A

Having two different alleles of a gene e.g Ff or

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17
Q

what is monohybriod inheritence?

A

The inheritence of a single gene

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18
Q

What is a problem with single gene crosses?

A

Most charcteristics are contorled by multiple alleles not just one

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19
Q

What are the monomers of DNA?

A

Nucleotides

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20
Q

What are DNA nucleotides made up of?

A

● Common sugar
● Phosphate group
● One of four bases: A, T, C or G

21
Q

State the full names of the four bases found in
nucleotides

A

Adenine
Thymine
Cytosine
Guanine

22
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
● Base connected to each sugar
● Complementary base pairs (A pairs with T, C pairs with G)
joined by weak hydrogen bonds

23
Q

Define genome

A

The entire genetic material of an organism

24
Q

What is a chromosome?

A

A long molecule fo DNA that carries genetic informationm

25
Q

Describe the method used to extract DNA from fruit

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 chilled ethanol into the test tube
  5. DNA precipitates forming a fibrous white solid
  6. Use a glass rod to collect the DNA sample
26
Q

Why is detergent added to the crushed fruit?

A

It disrupts the cell membranes, releasing DNA into solution

27
Q

Why is salt added to the crushed fruit ?

A

Salt encourages the precipitation of DNA

28
Q

Why is chilled ethanol added ratehr than water ?

A

DNA is insoluble in ethanol, encouraging the precipitation

29
Q

Explain how a gene codes for a protein

A

● A sequence of three bases in a gene forms a triplet
● Each triplet codes for an amino acid
● The order of amino acids determines the structure
(i.e. how it will fold) and function of protein formed

30
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.

31
Q

What is protein synthasis

A

The formation of a protein from a gene

32
Q

What are the two stages of protein synthasis?

A

-Transcription
-Translation

33
Q

What does transcription involve?

A

The formation of mRNA from a DNA template

34
Q

Outline transcription

A
  1. DNA double helix unwinds
  2. RNA polymerase binds to a specific base sequence of non-coding
    DNA in front of a gene and moves along the DNA strand
  3. DNA polymerase joins free RNA nucleotides to complementary bases
    on the coding DNA strand
  4. mRNA formation complete. mRNA detaches and leaves the nucleus.
35
Q

Describe the difference between mRNA and DNA

A

● mRNA is single stranded whereas
DNA is double stranded

● mRNA uses U whereas DNA uses T

36
Q

Why is mRNA used in translation rather than DNA?

A

DNA is too large to leave the nucleus so cannot reach the ribosome.

37
Q

What does translation involve?

A

A ribosome joins amino acids in a
specific order dictated by mRNA to form a protein.

38
Q

Outline translation

A
  1. mRNA attaches to a ribosome
  2. Ribosome reads the mRNA bases in triplets. Each triplet codes
    for one amino acid which is brought to the ribosome by a tRNA
    molecule
  3. A polypeptide chain is formed from the sequence of amino
    acids which join together
39
Q

How is a tRNA molecule adapted to its function?

A

Each tRNA molecule has an anticodon which is specific to the codon of the amino acid that it carries.

40
Q

What is a mutation?

A

A random change in the base sequence of DNA which results in genetic variants

41
Q

What is non-coding DNA?

A

DNA which does not code for a protein but instead controls gene expression

42
Q

Outline how the work of Mendel helped scientists to develop their understanding of genetics

A

● Mendel studied the inheritance of different phenotypes of pea plants
● He established a correlation between parent and offspring phenotypes
● He noted that inheritance was determined by ‘units’ passed on to
descendants
● Using gene crosses, he devised the terms ‘dominant’ and ‘recessive’

43
Q

Why was Mendel’s work initially overlooked?

A

Scientist’s didn’t understand Mendel’s work as there was no knowledge of genes or DNA at the time.

44
Q

What is a mutation?

A

A random change to the base sequence in DNA which results in genetic variants

45
Q

State the three types of gene mutation

A

● Insertion
● Deletion
● Substitution

46
Q

How may a gene mutation affect an organism’s
phenotype?

A

● Neutral mutation does not change the sequence of amino acids.
Protein structure and function same. No effect on phenotype.
● Mutation may cause a minor change in an organism’s phenotype e.g.
change in eye colour.
● Mutation may completely change the sequence of amino acids. This
may result in a non-functional protein. Severe changes to phenotype.

47
Q

What is the Human Genome Project?

A

● Scientific research project involving thousands of
scientists across the globe which successfully mapped the
entire human genome

● Scientists now aim to identify the function of every gene in
the human genome

48
Q

How can the results of the Human
Genome Project be applied to medicine?

A

● Enables scientists to understand how lifestyle factors interact with genes -
identifying predisposition to disease and possible preventions
● Disease-causing alleles identified more rapidly and the appropriate
treatments prescribed earlier on
● Scientists can predict an individual’s response to certain drugs. New drugs
can be developed which are tailored to a specific allele.

49
Q

What are drawbacks associated with the discoveries of the Human Genome Project?

A

● Knowledge of predisposition to a disease can be stressful

● Societal pressure influencing the decision to have children

● Discrimination by employers, insurance firms etc.

Biology Paper 1 (5 decks)

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