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GCSE - Biology > Topic 3 - Genetics > Flashcards

Topic 3 - Genetics Flashcards

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1
Q

What is sexual reproduction?

A

Reproduction involving production of gametes by meiosis

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2
Q

What happens during sexual reproduction?

A

A gamete from each parent fuses to form a zygote.

Genetic info from each gamete is mixed - zygote = unique.

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3
Q

What are gametes?

A 
Sex cells (sperm cells/egg cells)
Haploid (half no of chromosomes)
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4
Q

What is meiosis?

A

Form of cell division involved in formation of gametes
Chromosome number is halved
Involves 2 divisions

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5
Q

What must occur prior to meiosis?

A

Interphase

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6
Q

Why is meiosis important for sexual reproduction?

A

Increases genetic variation

Ensures resultant zygote is diploid

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7
Q

Advantages of sexual reproduction?

A

Creates genetic variation, increasing probability of species adapting to and surviving environmental changes

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8
Q

Disadvantages of sexual reproduction

A

2 parents needed. Makes difficult in endangered populations or species which exhibit solitary lifestyles.
More time + energy required = fewer offspring produced.

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9
Q

What is asexual reproduction?

A

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

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10
Q

Advantages of asexual reproduction ?

A

Only 1 parent needed
Lots of offspring produced in short time - enables rapid colonisation of area + reduce competition from other species
Requires less emergy

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11
Q

Disadvantage of asexual reproduction?

A

No genetic variation (except spontaneous mutations) reducing probability of species being able to adapt to environmental changes.

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12
Q

What type of reproduction is meiosis used for?

A

Sexual

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13
Q

What is DNA

A

Double stranded polymer of nucleotides, wound to form a double helix

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14
Q

What are the monomers of DNA?

A

Nucleotides

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15
Q

What are DNA nucleotides made up of?

A

Common sugar
Phosphate group
One of 4 bases - A T C G

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16
Q

State the full names of the 4 bases found in nucleotides

A

Adenine
Thymine
Cytosine
Guanine

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17
Q

Describe how nucleotides interact to form a molecule of DNA

A

Sugar + phosphate molecules join to form sugar-phosphate backbone in each strand.
Base connected to each sugar.
Complementary base pairs joined by weak hydrogen bonds.

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18
Q

Define genome

A

The entire genetic material of an organism

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19
Q

What is a chromosome?

A

A long coiled molecule of DNA that carries genetic info in form of genes

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20
Q

Define gene

A

A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein

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21
Q

Describe the method used to extract DNA from fruit

A
  1. Place piece of fruit in beaker + crush
  2. Add detergent + salt. Mix.
  3. Filter mixture + collect liquid in test tube
  4. Pour chilled ethanol into test tube
  5. DNA precipitates forming a fibrous white solid
  6. Use glass rod to collect DNA sample
22
Q

Why is detergent added to crushed fruit?

A

Disrupts cell membranes, releasing DNA into solution

23
Q

Why is salt added to the crushed fruit?

A

Encourages precipitation of DNA

24
Q

Why is chilled ethanol added rather than water?

A

DNA is insoluble in ethanol, encouraging its precipitation.

25
Q

What did Mendel study?

A

He studied inheritance of diff phenotypes of pea plants.

26
Q

What did Mendel establish a correlation between?

A

Parent and offspring phenotypes

27
Q

What did Mendel note about inheritance?

A

It was determined by ‘units’ passed on to descendants

28
Q

What is a mutation?

A

Random change in base sequence of DNA resulting in genetic variants

29
Q

What’s the effect of a gene mutation in coding DNA?

A

If mutation changes amino acid sequence, protein structure + function may change

30
Q

What is non-coding DNA

A

DNA which doesn’t code for protein but controls gene expression

31
Q

Why was Mendel work overlooked initially?

A

Scientists didn’t understand it as there was no knowledge of genes or DNA at the time

32
Q

What is a chromosome?

A

Long coiled molecule of DNA that carries genetic info in form of genes

33
Q

Define gene

A

A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein

34
Q

What are alleles?

A

Different versions of the same gene

35
Q

Define genotype

A

An organisms genetic composition, describes all alleles

36
Q

Define phenotype

A

An organisms observable characteristics due to interactions of the genotype + environment

37
Q

Define homozygous

A

Having 2 identical alleles of a gene

Eg: FF or ff

38
Q

Define heterozygous

A

Having 2 different alleles of a gene

Eg: Ff

39
Q

What is a dominant allele?

A

Describes an allele that is always expressed

Represented with capital letter (F)

40
Q

What is a recessive allele?

A

Allele that is only expressed in the absence of a dominant allele
Represented with small letter (f)

41
Q

What is a monohybrid inheritance?

A

Inheritance of a single gene

42
Q

What is the problem with single gene crosses?

A

Most characteristics are controlled by multiple alleles rather than just one

43
Q

What are sex chromosomes?

A

A pair of chromosomes that determine sex:
Males = XY
Females = XX

44
Q

Why does the inheritance of a Y chromosome mean that an embryo develops into a male?

A

Testes development in an embryo is stimulated by a gene present on the Y chromosome

45
Q

A couple have a child. What’s the probability that the child is female?

A

50% chance

46
Q

How can monohybrid inheritance be represented, other than a punnet square?

A

Family pedigree

47
Q

What is a sex-linked characteristic?

A

A characteristic that is coded for by an allele found on a sex chromosome

48
Q

What is co-dominance?

A

When 2 dominant alleles are expressed together in same individual

49
Q

When are multiple alleles present?

A

When 3 or more alleles are present at same loci

50
Q

An example of co-dominance/multiple alleles?

A

ABO blood group system

51
Q

Is the O allele recessive or dominant?

A

Recessive

52
Q

What are the A and B alleles?

A

Dominant

GCSE - Biology (7 decks)

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