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GCSE WJEC Biology > Topic 9 - DNA and Inheritance > Flashcards

Topic 9 - DNA and Inheritance Flashcards

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1
Q

What is a genome?

A

The genome is the entire genetic material of an organism.

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2
Q

What is DNA?

A

DNA is a double-helix polymer, which means it is a polymer made up of two strands forming a twisted, ladder shape.

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3
Q

What is a gene?

A

A gene is a small section of DNA that codes for a sequence of amino acids, which combine to give a specific protein.

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4
Q

What is a chromosome?

A

Long strands of DNA are coiled up to form chromosomes containing many genes.

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5
Q

What is a nucleotide?

A

Units that repeat throughout the structure of DNA are called nucleotides. Each of these is made up of a sugar, with a phosphate and a base attached to the sugar.

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6
Q

What is a polymer?

A

A large, chain-like molecule, extending for hundreds or thousands of atoms joined by strong covalent bonds.

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7
Q

What are the 4 bases?

A

Thymine - Adenine

Guanine - Cytosine

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8
Q

How is DNA held together?

A

By the attractions between 2 opposite bases

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9
Q

Which part of DNA do the sugar and phosphate make up?

A

The long strands

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10
Q

What is a codon?

A

A specific sequence of three bases that codes for a specific amino acid. This is known as the ‘triplet code’.

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11
Q

What significance does the order of the bases have in protein synthesis?

A

The order of the bases on the DNA tells us the order for combining amino acids to create particular proteins.

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12
Q

How are different proteins made?

A

The protein made by a gene is different because each gene has a different sequence of bases.

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13
Q

What is a ‘DNA fingerprint’?

A

Each person has a unique set of chromosomes which can be used to identify them using genetic profiling.

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14
Q

Genetic Profiling Step 1

A

Isolation - DNA from an individual is taken (e.g. through a cheek swab) and extracted from the cell’s nucleus.

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15
Q

Genetic Profiling Step 2

A

Fragmentation - Chromosomes are broken up into shorter segments of DNA.

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16
Q

Genetic Profiling Step 3

A

Separation - Using electrophoresis, whereby an electric current is passed through gel, the fragments of DNA are separated out according to size.

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17
Q

Genetic Profiling Step 4

A

Comparison - The fragments of DNA can then be compared to other DNA fingerprints to work out whether two DNA fingerprints are the same, or to identify whether certain genes are present.

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18
Q

What can genetic profiling be used for?

A

Identifying disease genes, classifying species, solving crimes and paternity tests.

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19
Q

How can genetic profiling be used to identify disease genes?

A

Comparing band patterns from different patients with the same genetic disease shows which genes the patients have in common, which helps identify genes linked to genetic disorders.

20
Q

How can genetic profiling be used to classify species?

A

Comparing band patterns of different species shows scientists how closely related different species are (in terms of evolution), which helps them classify species.

21
Q

How can genetic profiling be used to solve crimes?

A

Comparing band patterns of any DNA found at a crime scene (e.g. from blood) with that of the victim and with different suspects can place suspects at the scene of the crime.

22
Q

How can genetic profiling be used to test paternity?

A

Comparing the band patterns from a child with that of its mother and with possible fathers, and discounting the genes inherited from the mother, it can be worked out which DNA came from the father.

23
Q

What are alleles?

A

Alleles are different forms of the same gene

24
Q

How are characteristics determined?

A

Humans have pairs of every gene and in one gene, each half of the pair may have different alleles. People’s characteristics are determined by the alleles that they have.

25
Q

What is a dominant allele?

A

A dominant allele is always expressed, regardless of the identity of the other allele. It is represented by a capital letter.

26
Q

What is a recessive allele?

A

A recessive allele is only expressed if the other allele is also recessive. It is represented by a lowercase letter.

27
Q

What is the phenotype?

A

A phenotype is an observed characteristic of an individual, determined by the interaction between the genotype and environment.

28
Q

What is the genotype?

A

Genotype refers to the combination of alleles an organism has.

29
Q

What does heterozygous mean?

A

A person with two different alleles (Bb)

30
Q

What does homozygous mean?

A

A person with two of the same alleles, homozygous recessive (bb) or homozygous dominant (BB).

31
Q

What is a monohybrid cross?

A

When the inheritance of traits is determined by a single gene.

32
Q

What kind of diagram can be used to show monohybrid crosses?

A

Punnett Squares

33
Q

Where are the parents’ genes drawn on a Punnett Square?

A

Along the top and left side, the possible offspring are then filled in on the grid.

34
Q

What are parents called on a Punnett Square?

A

F0 generation

35
Q

What are the offspring called on a Punnett Square?

A

F1 generation

36
Q

What would the offspring’s offspring be called on a Punnett Square?

A

F2 generation

37
Q

What else can Punnett Squares represent?

A

Selfing, where plants pollinate themselves; the plant is both ‘parents’.

38
Q

What are the sex chromosomes of a female?

A

Females are XX, so an egg contains one X chromosome.

39
Q

What are the sex chromosomes of a male?

A

Males are XY, so a sperm contains either one X or one Y chromosome.

40
Q

What is genetic engineering?

A

Genetic engineering involves changing the genetic material of an organism by removing, changing or inserting individual genes from another source to produce the desired characteristic.

41
Q

What can genetic engineering be used for?

A

Inserting genes into crop plants to provide additional vitamins, into bacteria to produce human insulin, into crop plants to give them resistance to herbicides or insects.

42
Q

What are the advantages of genetic engineering?

A

Preventing inherited diseases, improving food production efficiency due to increased yields, providing missing nutrients, no complications so far.

43
Q

What are the disadvantages of genetic engineering?

A

Negatively impact wild flower and insect populations i.e. ‘superweed’, thus reducing biodiversity, long-term effects on human health, unethical to create new life.

44
Q

What does GM stand for?

A

Genetically modified

45
Q

What is a permanent change in the nucleotide sequence of DNA called?

A

A mutation

GCSE WJEC Biology (9 decks)

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