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AQA Biology GCSE > Inheritance - DNA > Flashcards

Inheritance - DNA Flashcards

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1
Q

Where is DNA found

A

in the chromosomes

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2
Q

what is DNA

A

a polymer made up of two strands forming a double helix

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3
Q

why is DNA our genetic material

A

because our DNA determines our inherited features

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4
Q

what is a gene

A

a small section of DNA on a chromosome

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5
Q

how are proteins made

A

by joining together amino acids

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6
Q

what do genes do

A

each gene codes for a specific sequence of amino acids to make a specific protein

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7
Q

what is the genome

A

the entire genetic material of an organism

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8
Q

what are the benefits of the human genome

A
  • understanding the human genome will help us search for genes that are linked to a specific disease, e.g - genes that are linked to cancer or Alzheimer’s
  • Understanding the human genome may help us understand and treat inherited disorders such as Cystic fibrosis
  • We can use the human genome to trace human migration patterns from the past, and this can help people discover their ancestry
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9
Q

what are DNA strands made from

A

nucleotides

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10
Q

what are nucleotides made up of

A
  • a sugar
  • a phosphate
  • a base
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11
Q

what does the circle represent in a nucleotide

A

the phosphate group

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12
Q

what does the pentagon represent in a nucleotide

A

the sugar

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13
Q

what does the rectangle represent in a nucleotide

A

the base

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14
Q

what does complementary mean in terms of DNA bases

A

the same bases always pair on opposite strands

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15
Q

which bases pair to which in DNA

A

A and T pair
C and G pair

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16
Q

how many different amino acids are there in humans

A

20

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17
Q

what is the order of amino acids in a protein determined by

A

the sequence of bases in the gene for that protein

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18
Q

Stages of protein synthesis

A
  1. Proteins are made in the cell cytoplasm on tiny structures called ribosomes
  2. To make proteins, ribosomes use the code in the DNA, and dna is found in the nucleus, and cant move our as its too big, so the cell needs to get the code from the DNA to the ribosomes
  3. This is done using a molecule called mRNA which is made by copying the code from the DNA. The mRNA acts as a messenger between the DNA and ribosomes- carrying the code between the two
  4. the correct amino acids are brought to the ribosomes in the correct order by carrier molecules
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19
Q

what are proteins

A

polymers of amino acids

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20
Q

what does the order of amino acids in a protein determine

A

its shape and function

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21
Q

what is mRNA

A

a single stranded molecule

22
Q

what is a mutation

A

a change to a base of DNA

23
Q

why might mutations not change an amino acid sequence

A

because different base triplets can sometimes encode for the same amino acid

24
Q

why might a mutation which changes the shape of a protein, have a massive effect on it

A
  • because the active site of the enzyme may change shape, so it’ll no longer attach to the substrate
  • if the mutation changes the shape of a structural protein such as collagen, it may lose it’s strength
25
Q

what do non coding parts of DNA do

A

they switch genes on and off, they tell genes when to produce proteins

26
Q

what would happen if a non - coding part of DBA was mutated

A

a gene may be turned off when it’s meant to be turned on, or vice versa
- meaning a cell would produce a protein that its not meant to have at the time
- this could have a very significant effect on the cell, eg uncontrolled mitosis leading to cancer

27
Q

what are alleles

A

versions of genes

28
Q

what is a genotype

A

something that tells us what alleles are present in a person

29
Q

meaning of homozygous alleles

A

having two copies of the same allele

30
Q

what is a phenotype

A

something that tells us the characteristics caused by the persons alleles

31
Q

what is heterozygous

A

when someone has two different alleles

32
Q

what is a dominant allele

A

an allele that will show in the phenotype even if there is only one copy present

33
Q

what is a recessive allele

A

an allele that will only show in the phenotype if two copies are present( so if no dominant alleles are present)

34
Q

what is cystic fibrosis

A

a disorder of the cell membranes

35
Q

what needs to happen in order for a person to have cystic fibrosis

A

they need to have two copies of the defective allele

36
Q

what is meant by a carrier of cystic fibrosis

A

when a person has one defective allele and one normal allele

37
Q

What is polydactyly

A

a disorder where someone is born with extra fingers or toes

38
Q

what type of allele is polydactyly caused by

A

dominant

39
Q

what is embryo screening

A

a process in which embryos are tested to see if they have the alleles for inherited disorders

40
Q

how does embryo screening work

A
  1. cell is taken out of and embryo is tested to see if it has the alleles for an inherited disorder
  2. Embryo which do not have the defective alleles are implanted into the woman
  3. These can help them develop healthy offspring
41
Q

what are issues around embryo screening

A
  • its expensive, and people think that the money should be spent elsewhere un the health service
  • implies that people with genetic problems are undesirable and this may cause prejudice
  • in the future we may be able to screen embryos to produce offspring with desirable features, this is also unethical
  • often, a large number of embryos are created, but only a small number are implanted, meaning that some healthy embryo are destroyed and people think its unethical
42
Q

what is gene therapy

A
  • correcting faulty alleles and using these to treat inherited disorders
43
Q

what chromosomes do males have

A

XY

44
Q

what chromosomes do females have

A

XX

45
Q

where does the first stage of protein synthesis happen

A

nucleus

46
Q

where does the second stage of protein synthesis take place

A

cytoplasm

47
Q

Summarise the stages of protein synthesis

A
  1. Transcription - the base sequence of the gene is copied into a complementary template molecule
    • scientists call this template mRNA and it is a single stranded molecule
  2. the mRNA then passes out of the nucleus into the cytoplasm
  3. Translation - In this stage, the mRNA molecule attaches to a ribosome. amino acids are then brought to the ribosome on carrier molecules
    • these carrier molecules are called tRNA
  4. the ribosome then reads the triplets of bases on the mRNA and uses this to join the correct amino acids in the correct order
  5. once the protein chain is complete, it now folds into its unique shape
48
Q

what happens when a protein formed

A

it folds into a unique shape

49
Q

What has to happen in order for someone to inherit cystic fibrosis

A

The person has to have two copies of the defective allele

50
Q

Why aren’t punnet squares that accurate?

A

Because they are just probabilities

51
Q

how do DNA bases in a gene code for specific chains of amino acids

A
  • each sequence of the three bases codes for one specific amino acids, so the order of the bases in the gene decides the order of amino acids in the chain
52
Q

advantages of embryo screening

A
  • will help people stop suffering from genetic disorders
  • treating these disorders. it’s the government and taxpayers a lot of money, screening to reduce the number of people suffering from these disorders could save money
  • parents can’t use it to select desirable characteristics as there are laws to stop screening going to far

AQA Biology GCSE (36 decks)

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