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GCSE Biology > Topic 3: Genetics > Flashcards

Topic 3: Genetics Flashcards

1
Q

What is sexual reproduction?

A

When genetic information from two organisms is combined to produce offspring which are genetically different to either parent

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2
Q

What are the steps of sexual reproduction?

A
  1. Parents produce haploid gametes (reproductive cells)
  2. Gametes fuse at fertilisation
  3. A diploid zygote is produced
  4. The zygote divides by mitosis and becomes an embryo
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3
Q

What are chromosomes?

A

Long molecules of DNA that normally come in pairs

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4
Q

What does haploid mean?

A

Contains half the number of chromosomes of normal cells

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5
Q

What does diploid mean?

A

Contains a full set of chromosomes

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6
Q

What is meiosis?

A

Type of cell division that produces four haploid daughter cells

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7
Q

Meiosis v Mitosis: uses

A

Meiosis - creating sex cells
Mitosis - growth and repair

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8
Q

Meiosis v Mitosis: type of reproduction

A

Meiosis - sexual
Mitosis - asexual

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9
Q

Meiosis v Mitosis: number of cells created

A

Meiosis - 4 cells
Mitosis - 2 cells

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10
Q

Meiosis v Mitosis: number of chromosomes in the cells produced

A

Meiosis - 23 chromosomes (haploid)
Mitosis - 46 chromosomes (diploid)

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11
Q

Meiosis v Mitosis: the created cells’s genetics

A

Meiosis - cells are genetically different
Mitosis - cells are genetically identical

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12
Q

What does asexual reproduction mean?

A

When a single parent produces genetically identical offspring e.g. mitosis

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13
Q

Advantages of asexual reproduction?

A

Fast compared to sexual reproduction

Only one parent needed - no energy wasted finding a mate

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14
Q

Disadvantages of asexual reproduction?

A

No genetic variation between offspring - whole population can be affected by unfavourable conditions

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15
Q

Advantages of sexual reproduction?

A

Variation in offspring - increased chance that some individuals in the species may survive a change in environment leading to evolution or natural selection

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16
Q

Disadvantages of sexual reproduction?

A

Need to find a mate - takes time and energy

Hard for isolated individuals

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17
Q

What is the structure of DNA?

A

A polymer made of two strands coiled into a double helix

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18
Q

What are the parts of a DNA strand?

A

Sugar-phosphate backbone
Phosphate
Sugar

The above are part of a nucleotide - the monomers that make up DNA

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19
Q

What are the complimentary base pairs?

A

A T
G C

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20
Q

What are complimentary bonds held together with?

A

Weak hydrogen bonds

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21
Q

Practical: how to extract DNA from fruit?

A
  1. Mash the fruit - to break down cell wall
  2. Add detergent, salt and proteases - detergent breaks down the cell membrane to release DNA, salt makes DNA stick together and proteases prevents the enzymes breaking down DNA
  3. Filter - to filter large and insoluble clumps of fruit and get rid of them
  4. Pour ice cold ethanol over the solution - precipitates DNA and makes it visible
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22
Q

What is a genome?

A

All an organisms DNA

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23
Q

What is a gene?

A

A small section of DNA found on a chromosome that codes for a particular protein

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24
Q

What are the processes in protein synthesis?

A

Transcription then translation

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25
Q

Where does transcription take place?

A

In the nucleus

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26
Q

What is the process of transcription?

A
  1. DNA strands unwinds because of helicase, then the RNA polymerase will bind with DNA as they have complimentary base pairs
  2. Base paring between DNA and RNA makes a complimentary mRNA strand
  3. The mRNA moves out of the nucleus and binds to the ribosome
27
Q

What is the difference between RNA and DNA?

A

RNA - single stranded & there are difference base pairs (A pairs with U and C pairs with G)
DNA - double stranded & the base pairs are different (A pairs with T and C pairs with G)

28
Q

Where does translation take place?

A

In the cytoplasm/ribosomes

29
Q

What are the steps of translation?

A
  1. mRNA leaves the nucleus and goes to the ribosome where they bind together
  2. tRNA brings amino acids to the ribosome
  3. Anticodons on the tRNA are complimentary to codons on the mRNA and they bind together
  4. Amino acids are therefore joined in the correct order
  5. The ribosome join the amino acids together making a polypeptide - which folds up to make the protein
30
Q

What is a mutation?

A

A random change to the base sequence of DNA

31
Q

What did Mendel study?

A

How characteristics in plants are passed on from one generation to the next

32
Q

What did Mendel find out when he bred a tall pea plant and a dwarf pea plant?

A

That a tall pea plant when bred with a dwarf pea plant made all tall pea plant offspring

33
Q

What were Mendels conclusions?

A
  1. Hereditary units determine characteristics
  2. Units are passed on to offspring unchanged
  3. The units can be dominant or recessive
34
Q

How did Mendel’s findings help other discoveries?

A

Scientists learnt about chromosomes
‘Units’ were named genes
Structure of DNA was able to be determined

35
Q

What is an allele?

A

A version of a gene

36
Q

What does dominant mean?

A

An allele that is always expressed

37
Q

What does recessive mean?

A

An allele that is only expressed when two copies are present

38
Q

What does homozygous mean?

A

When both of an organisms alleles for a trait are the same
E.g. bb or BB

39
Q

What does heterozygous mean?

A

When an organisms alleles for a trait are different
E.g. Bb

40
Q

What is a genotype?

A

An organisms combination of alleles

41
Q

What is a phenotype?

A

The characteristics an organism has

42
Q

What does a punnet square show?

A
  1. The gametes’ genotypes of both parents (female and male)
  2. The offspring’s genotypes
43
Q

What can a punnet square represent?

A

The likelihood the offspring will have a certain characteristic, blood group or what it’s sex will be

44
Q

What do family pedigrees have?

A
  1. A key showing males & females specifically: those that are affected by the disease, those that are carriers, those that are unaffected
  2. Horizontal lines link the parents
  3. Vertical lines connect parents to offspring
45
Q

What is a family pedigree similar to?

A

Family tree

46
Q

What can family pedigree represent?

A

The likelihood the offspring will have the disease and what it’s sex will be

47
Q

What’s a sex linked disorder?

A

When the allele that codes for a disorder is located on a sex chromosome

48
Q

What can sex linked disorders of parents and how it’ll affect offspring be represented on?

A

Punnet square

49
Q

How is a sex linked disorder shown?

A

E.g. X^N X^n
E.g. X^n X^n
E.g. X^N X^N

50
Q

How is a genotype shown where one chromosome is affected not the other?

A

E.g. X^n Y

Unaffected chromosome stays the same

51
Q

What are the different alleles for the different blood type?

A

I^O
I^A
I^B

52
Q

Which of the blood type alleles are codominant?

A

I^A
I^B

53
Q

What are the 4 blood groups?

A

O
A
B
AB

54
Q

What blood type allele is recessive?

A

I^O

55
Q

What can blood groups of parents and how it’ll affect offspring be represented on?

A

Punnet square

56
Q

What is variation?

A

Differences in the characteristics of organisms

57
Q

Where does genetic variation come from?

A
  1. Sexual reproduction - since offspring made aren’t identical
  2. Mutations
58
Q

What affect do mutations have on phenotypes?

A

It depends

59
Q

What happens in environmental variation?

A

Differences in the conditions in which organisms develop cause variation - they get acquired characteristics
E.g. leaf colour

60
Q

What happens in genetic and environmental variation?

A

For most characteristics, variation is caused by both genetics and the environment
E.g. plant height

61
Q

What has the human genome project done?

A

Worked out the complete human genome

62
Q

What has the human genome project helped do?

A
  1. Predict and prevent diseases - knowing which gene leads to what disease can help doctors tailor advice and treatments
  2. Test and treat inherited disorders - people can be tested early and we can develop better treatments
  3. Develop new and better medicines - drugs can be tailored to individuals and there is potential for more effective treatments with fewer side effects
63
Q

What is the negative of the human genome project?

A

Could lead to some people to being more stressed & more discrimination by employers and insurers

GCSE Biology (9 decks)

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