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Bio PPQs > Genetics and inheritance > Flashcards

Genetics and inheritance Flashcards

1
Q

A breeder crossed a black male cat with a black female cat on a number of occasions. The female cat produced 8 black kittens and 4 white kittens.

Explain the evidence that the allele for white fur is recessive.

(1 mark)

A
  • Parents are heterozygous
  • Kittens recieve white allele from parents/ black cat
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2
Q

A cat breeder expects an equal no. of 2 types of kittens. Explain why the actual numbers were different from those expected.

(1 mark)

A
  • Offspring ratios are a probablitly
  • Gametes may not be produced in equal numbers
  • Random fusion of gametes
  • Small sample
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3
Q

Explain what is meant by codominant alleles

(1 mark)

A
  • Both alleles are equally expressed within the phenotype
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4
Q

Explain what is meant by the term phenotype

(2 marks)

A
  • Expression due to genetic constitution
  • Due to environment
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5
Q

Males are more likely than female to show a phenotype produced by a recessive allele carried on the X chromosome. Explain why

(2 marks)

A
  • Males only have 1 allele
  • Females need 2 recessive alleles
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6
Q

Explain how a substitution mutation leads to the formation of a non-functioning enzyme

(3 marks)

A
  • Change in amino acid sequence
  • Change in hydrogen/ ionic/ disulphide bonds alters tertiary structure
  • Substrate not compementary/ cannot bind to active site
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7
Q

Describe how alterations to tumour supressor genes can lead to the development of tumours

(3 marks)

A
  • Increased methylation of TSG
  • Mutation
  • Tumour supressor genes are not transcribed

When the queation asks about “alterations” you must specify the alteration (mutation)

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8
Q

Papaya plants reproduce sexually by means of seeds. Papaya plants grown from seeds are very variable in their yield. Explain why.

(2 marks)

A
  • Independant segregation
  • Random fertilisation
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9
Q

Explain the advantage of growing plants from tissue culture rather than from seeds

(1 mark)

A
  • All plants will have desired characteristics
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10
Q

Describe the method used to find the mean no. of capillaries per mm^2 of samples of heart muscle tissue

(4 marks)

A
  • Measure diameter of field of view and calculate area
  • Using micrometer slide and eyepiece graticule
  • Count no. of capillaries in large no. of fields of view and calculate mean
  • Select fields of view randomly

Always mention how to improve validity

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11
Q

Define what is meant by epigenetics

(2 marks)

A
  • Heritable chnages in gene function
  • Without changes to base sequence of DNA
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12
Q

Explain how increased methylation could lead to cancer

(3 marks)

A
  • Methyl groups added to a tumour supressor gene
  • The transcription of tumour supressor genes is inhibited
  • Leading to uncontrolled cell division
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13
Q

Give one way in which benign tumours differ from malignant tumours

(1 marks)

A

Cells of benign tumours cannot metastasise

(1 mark)

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14
Q

Explain how the methylation of tumour supressor genes can lead to cancer

(3 marks)

A
  • Methylation prevents transcription of gene
  • Protein not produced that prevents cell division
  • No control of mitosis
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15
Q

Explain how an activated oestogen receptor affects the target cell

(2 marks)

A
  • Receptor/ transcription factor binds to promoter which stimuates RNA polymerase
  • Transcribes gene
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16
Q

Describe 2 ways in which both malignant and benign tumours may cause harm to the body

(2 marks)

A
  • May damage organ concerned
  • May cause blockages/ obstructions
  • May damage/ exert pressure on other organs

(Max 2)

17
Q

Suggest why people with a family history of no cancer are at a greater risk of cancer than those with no family history of cancer

(1 mark)

A
  • Cancer has genetic component/ may have inherited gene which gives predisposition to cancer
18
Q

Describe he role of 2 named types of enzymes used to insert DNA fragments into plasmids

(2 marks)

A
  1. Restrtictionj endonuclease to cut plasmid/ vector
  2. DNA ligase to join gene to plasmid/ vector

2 mark question means little detail but it’s imortant to remeber its hydrolysis and condensation

19
Q

Suggest and explain how delayed insertion of a gene could produce offspring of a transgenic species without the desired characteristic

(2 marks)

A
  • Cell division has occured before the gene is added
  • Gametes fo not recieve the gene
20
Q

What is a DNA probe

(2 marks)

A
  • Short single strand of DNA
  • Bases complementary with gene/ DNA
21
Q

During genetic screening, the DNA is treated to form single strands. Explain why.

(1 mark)

A

So DNA probe binds

22
Q

Explain the role of reverse transcriptase in reverse transcriptase PCR

(1 mark)

A

Produces (c)DNA using (m)RNA

23
Q

Explain the role of DNA polymerase in PCR

(1 mark)

A

Joins nucleotides to produce complementary strands of DNA

24
Q

In recombinant DNA technology, an insect gene is inserted into plant DNA. The plant is able to synthesise the insect protein.
Explain why this is possible.

(3 marks)

A
  • Genetic code is universal/ triplets in DNA always code for the same amino acid
  • Insect DNA can be transcribed
  • Can be translated
25
Q

Name the type of enzyme used to produce the cDNA

(1 mark)

A

Reverse transcriptase

26
Q

Recombinant gene tech question

Explain the purpose fo attaching a gene that codes for a protein that glows green under florescent light.

(2 marks)

A
  • Acts as a marker gene to show that the gene has been expressed
  • Only implant cells that show fluoresence
27
Q

Suggest one reason why very few live birhs result from embryos implanted to produce transgenic animals

(2 marks)

A
  • Mutation/ DNA may be damaged
  • May interfere with gene expression
28
Q

Explain how electrophoresis seperates fragments of DNA

(2 marks)

A
  • Move towards anode
  • Different rates of movement related to charge
29
Q

Explain why radioactive DNA probes are used to locate specific DNA fragments

(2 marks)

A
  • DNA invisible on gel
  • Allows detection
30
Q

Explain why the DNA of different species shows difference in base sequence

(2 marks)

A
  • Different genes (due to mutations), base sequence determines protein
  • Different species have different protein structures
31
Q

The length of replicated DNA fragments is different for each species. Explain why this is important in identifying the species involved.

(3 marks)

A
  • Electrophoresis separates DNA
  • So they can be identified by position on gel
  • Smaller/ shortest fragments travel furthest
32
Q

Describe the polymerase chain reaction

(6 marks)

A
  • Heat DNA
  • Breaks H bonds/ seperates strands
  • Add primers
  • Add nucleotides
  • Cool
  • (to allow) binding of nucleotides/ primers
  • DNA polymerase
  • Joins nucleotides together
  • Repeat cycle many times

Bio PPQs (7 decks)

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