B13 - Reproduction PART 2 OF ACC VERSION

Question 1

How do the cells read the DNA sequences ?

Answer 1

The cells read the DNA sequences as triplets of bases .

Question 2

What does each triplet base encode for ?

Answer 2

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

Question 3

How many stages does protein synthesis have ?

Answer 3

Protein synthesis consists of two stages .

Question 4

Where does the first stage of protein synthesis take place ?

Answer 4

In the nucleus .

Question 5

Where does the second stage of protein synthesis take place ?

Answer 5

In the cytoplasm .

Question 6

What is the first stage of protein synthesis called ?

Answer 6

Transcription .

Question 7

What happens in transcritpion ?

Answer 7

• 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 .

Question 8

c

Answer 8

Single stranded molecule .

Question 9

What is the second stage of protein synthesis called ?

Answer 9

Translation .

Question 10

What happens in translation ?

Answer 10

• 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 .

Question 11

What happens in translation (part two )

Answer 11

• 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 .

Question 12

What is a mutation ?

Answer 12

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

Question 13

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

Answer 13

This had no change in the amino acid sequence .

Question 14

Why did the mutation not make a difference ?

Answer 14

• 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 ).

Question 15

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

Answer 15

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

Question 16

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

Answer 16

-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 .)

Question 17

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

Answer 17

-It may lose its strength .

Question 18

Chromosomes contain coding parts of DNA and …

Answer 18

-Non-coding parts of DNA .

Question 19

What do non-coding parts of DNA do ?

Answer 19

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

Question 20

What can mutation do to non-coding genes ?

Answer 20

• 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 .

Question 21

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

Answer 21

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

Question 22

What is Nonsense ?

Answer 22

-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 .

Question 23

What is Missense ?

Answer 23

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

Question 24

What is Silent ?

Answer 24

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

Question 25

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

Answer 25

-The protein will be unchanged .

Question 26

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

Answer 26

causing the protein to be non-functional .

Question 27

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

Answer 27

giving it a new function or making it more effective .

Question 28

-Where do chromosomes come from ?

Answer 28

- One chromosome pair comes from your father . - The other Chromosome pair comes from your mother .

Question 29

What are alleles ?

Answer 29

Alleles are different versions of the gene | (genes come in different versions )

Question 30

What is geneotype ?

Answer 30

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

Question 31

What is homozygous?

Answer 31

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

Question 32

What is phenotype ?

Answer 32

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

Question 33

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

Answer 33

:))

Question 34

What is heterozygous

Answer 34

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

Question 35

What is a dominant allele ? Give e.g .

Answer 35

- 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 .

Question 36

What is recessive allele ? Give e.g .

Answer 36

- 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 .

Question 37

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

Answer 37

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

Question 38

What is Cystic Fibrosis a disorder of ?

Answer 38

-Cystic Fibrosis is a disorder of cell membranes .

Question 39

What is Cystic Fibrosis controlled by ?

Answer 39

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

Question 40

What is the allele for normal cell membrane function?

Answer 40

Dominant

Question 41

What is the allele for defective cell membranes ?

Answer 41

Recessive .

Question 42

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

Answer 42

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 .

Question 43

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

Answer 43

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

Question 44

What is wrong with Punnet diagrams .

Answer 44

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

Question 45

What happens when people have Polydactyl ?

Answer 45

-People with polydactyl have extra fingers or toes .

Question 46

What allele causes Polydactyl ?

Answer 46

-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 .

Question 47

Can you be a carrier of Polydactyl ?

Answer 47

No - it is a dominant allele .

Question 48

WHat is a solution to inherited disorders to prevent it ?

Answer 48

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 .

Question 49

What is one problem with embryo screening ?

Answer 49

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

Question 50

What is the second problem with embryo screening ?

Answer 50

-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 .

Question 51

What is the third problem with embryo screening ?

Answer 51

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

Question 52

What is gene therapy ?

Answer 52

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 .

Question 53

What do family trees show ?

Answer 53

Only phenotypes not genotypes .

Question 54

Answer questionns on family tree video on free science lessons ?

Answer 54

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