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Biology > B13 - Reproduction PART 2 OF ACC VERSION > Flashcards

B13 - Reproduction PART 2 OF ACC VERSION Flashcards

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1
Q

How do the cells read the DNA sequences ?

A

The cells read the DNA sequences as triplets of bases .

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2
Q

What does each triplet base encode for ?

A

Each triplet encodes for a specific amino acid in the protein .

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3
Q

How many stages does protein synthesis have ?

A

Protein synthesis consists of two stages .

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4
Q

Where does the first stage of protein synthesis take place ?

A

In the nucleus .

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5
Q

Where does the second stage of protein synthesis take place ?

A

In the cytoplasm .

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6
Q

What is the first stage of protein synthesis called ?

A

Transcription .

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7
Q

What happens in transcritpion ?

A
  • In this stage , the base sequence of the gene is copied into a complementary template molecue .
  • Scientists ca; this template RNA or mRNA for short .
  • The mRna now passes out of the nucleus into the cytoplasm .
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8
Q

c

A

Single stranded molecule .

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9
Q

What is the second stage of protein synthesis called ?

A

Translation .

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10
Q

What happens in translation ?

A
  • In this stage , the mRNA molecule attaches to a ribosome .
  • Amino acids are now brought to the ribosome on carrier molecules .
  • These carrier moelcules are called transfer RNA or tRNA for short .
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11
Q

What happens in translation (part two )

A
  • The ribosome now reads the triplets of bases on the mRNA and uses this to join together the correct amino acids in the correct order .
  • Once the prtein chain is complete , it now folds innto the unique shape .
  • The shape enables the protein to do its job .
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12
Q

What is a mutation ?

A

A mutation is a change in the genetic material of an otganism .

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13
Q

(Check mutation sheet )What would have happened when a single base had changed but the same sequence ?

A

This had no change in the amino acid sequence .

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14
Q

Why did the mutation not make a difference ?

A
  • As different base triplets can sometimes encode for the same amino acid sequence .
  • In this case the mutation had no effect on the protein’s shape or function . (most mutations have no effect on the protein ).
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15
Q

(Check mutation sheet) What has the different amino acids done ?

A
  • They have altered the shapeof the protein .
  • This has altered the shape of the protein .
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16
Q

-What can happen if the shape of the protein is altered ?

A

-Tjis caan have a dramtic effect on the protein funciton , (active site of an enxyme may change shape and no longer attach to the substrate .)

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17
Q

What could happen if a mutation changed the shape of a structural protein (collagen ) ?

A

-It may lose its strength .

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18
Q

Chromosomes contain coding parts of DNA and …

A

-Non-coding parts of DNA .

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19
Q

What do non-coding parts of DNA do ?

A

-These regions switch genes on and off - tell genes when to produce proteins .

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20
Q

What can mutation do to non-coding genes ?

A
  • Mutations in these non-coding regions can affect how genes are swtiched on or off .
  • A gene may be turned on when it is menant to be turned off .
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21
Q

What would happen if a geen is turned on when it shouldn’t be in the diagram ?

A

-Cell could produce a protein it isn’t meant to .
This could have a significant effect on the cell - uncontrolled mitosis - Cancer .

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22
Q

What is Nonsense ?

A

-Occurs when a substitution of a base occurs to leading to a premature ‘stop codon’ being coded for . The protein would either not form or would not function correctly .

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23
Q

What is Missense ?

A

-Occurs when a change in base leads to a different amino acid being coded for . The protein would not form or would function corrrectly .

24
Q

What is Silent ?

A

Occurs when a substituition of a base still codes for the same aminoa cid as the original base .

25
Q

If a base changes , but the codon still codes for the same amino aicd , what will happen ?

A

-The protein will be unchanged .

26
Q

If a base changes , a different amino acid ay be used in the protien meaning …

A

causing the protein to be non-functional .

27
Q

Soemtims a mutation will cause a beenficial change in a protein …

A

giving it a new function or making it more effective .

28
Q

-Where do chromosomes come from ?

A
  • One chromosome pair comes from your father .
  • The other Chromosome pair comes from your mother .
29
Q

What are alleles ?

A

Alleles are different versions of the gene

(genes come in different versions )

30
Q

What is geneotype ?

A

The genotype of a person is the genetic makeup of an individual for a particular characteristic

31
Q

What is homozygous?

A

-If the person has two copies of the same allele scientists say they are homozygous . (E,E)(e,e)

32
Q

What is phenotype ?

A

The phenotpe of a person tells us the characterisics caused by the persons alleles .

33
Q

On the alleles sheet , state the genotype for the three drawings , and what the phenotype is .

A

:))

34
Q

What is heterozygous

A

If the person has two different alleles , this is known as heterozygous (E,e).

35
Q

What is a dominant allele ? Give e.g .

A
  • A dominat allele will show in the phenotype even if there is only one copy present .
  • E.g the allele for wet ear was (E) is dominant so the persons phenotype is wet ear wax .
36
Q

What is recessive allele ? Give e.g .

A
  • A recessive allele (e) , will only show in the phenotype if two copies are present . In other words if no dominant allele is present .
  • E,g (e,e)- there is no dominant allele (E) , so the phenotype is dry ear wax .
37
Q

What are many characteristics a result of ? Give an example ,

A

Many characteristics are the result of many genes acting together , e.g height .

38
Q

What is Cystic Fibrosis a disorder of ?

A

-Cystic Fibrosis is a disorder of cell membranes .

39
Q

What is Cystic Fibrosis controlled by ?

A

-Cystic fibrosos is controlled by a single gene , which has two alleles .

40
Q

What is the allele for normal cell membrane function?

A

Dominant

41
Q

What is the allele for defective cell membranes ?

A

Recessive .

42
Q

So as the allele is recessive for Cystic Fibrosis , how does offspring get Cystic Fibrosis ?

A

In order to have Cystic Fibrosis , the person has to have two copies of the defective allele (recessive allele ) - have to inherit a defective allele from both parents .

43
Q

What is a person with one defective allelle and normal cell for Cystic Fibrosis ?

A

They do not have cystivc fibrosis , but are known as a CARRIER of the Cystic Fibrosis allele .

44
Q

What is wrong with Punnet diagrams .

A

The percentages are just probabilities , so all of the offspring could be carriers , or all the offspring could be unaffected .

45
Q

What happens when people have Polydactyl ?

A

-People with polydactyl have extra fingers or toes .

46
Q

What allele causes Polydactyl ?

A

-Dominant alleles - meaning if a person has ONE copy of the polydactly and a NORMAL allele , they will have Polydactyl as dominant allele characteristics are always shown .

47
Q

Can you be a carrier of Polydactyl ?

A

No - it is a dominant allele .

48
Q

WHat is a solution to inherited disorders to prevent it ?

A

Embryo screening - in embryo screening , embryos are tested to see if they have alleles for inherited disorders .
-Embryos which do not have defective allels are implanted into the woaman . These can develop into healthy offspring .

49
Q

What is one problem with embryo screening ?

A

-Embryos screening is expensive - some people think the money should be spent elsewhere in the Health Service .

50
Q

What is the second problem with embryo screening ?

A

-Often a large number of embryos are created but , only a small number are implanted . This means that some healthy embryos are destroyed and some people think that is unethical .

51
Q

What is the third problem with embryo screening ?

A

-In the future , we may be able to screen embryos to produce offspring with desirable features (e.g taller) - many find this unethical .

52
Q

What is gene therapy ?

A

In the future , scientists may be able to correct faulty alleles and use this to treat inheried disorders - but at the moment , this is still experimental .

53
Q

What do family trees show ?

A

Only phenotypes not genotypes .

54
Q

Answer questionns on family tree video on free science lessons ?

A

.

55
Q
A

Biology (25 decks)

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