Cell Division and Inheritance Revision 3 · (c)€€€€ Bob and Carol know that there is a risk...

Cell Division and Inheritance Revision 3

69 minutes

69 marks

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Q1. Cystic fibrosis is an inherited disorder that can seriously affect health.

(a) Which one of these is affected by cystic fibrosis?

Draw a ring around your answer.

blood cell membranes kidneys nervous system (1)

(b) The diagram shows the inheritance of cystic fibrosis in a family. The allele that produces cystic fibrosis is recessive.

(i) Explain why Alice inherited cystic fibrosis.

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(ii) Explain why Ted did not inherit cystic fibrosis.

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(c) Bob and Carol know that there is a risk that their next baby will have cystic fibrosis.

Embryos can be screened for the allele that produces cystic fibrosis.

Many people support the screening of embryos, but others do not.

(i) Suggest one reason why many people support the screening of embryos for the cystic fibrosis allele.

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(ii) Suggest one reason why many people are against the screening of embryos for the cystic fibrosis allele.

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(Total 7 marks)

Q2. In the 1850s, Gregor Mendel carried out breeding experiments using peas.

(a) The importance of Mendel’s work was not recognised until the early 1900s.

Explain why.

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(b) A student repeated one of Mendel’s experiments.

The flow chart shows her procedure.

The diagram shows a representative sample of seeds produced by second generation plants.

(i) Describe how the student could obtain a sample that is representative of seeds produced by the second generation.

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(ii) What was the approximate ratio of yellow seeds to green seeds in the seeds produced by the second generation?

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(iii) Seed colour in peas is controlled by a single gene which has two alleles.

Use a genetic diagram to show why this ratio of yellow seeds to green seeds was produced by the second generation.

Use the symbol A to represent the dominant allele, and a to represent the recessive allele. (4)

(Total 8 marks)

Q3. The diagram shows a spider plant during one type of reproduction.

Complete the sentences using words from the box.

(a) The colour and shape of the leaves of a spider plant are known

as ................................................................................................................................ (1)

asexual characteristics chromosomes

gametes genes mitosis sexual

(b) The shape of the leaves is controlled by .................................................................... (1)

(c) The thread-like structures inside the nucleus of the cells are

called .......................................................................................................................... (1)

(d) The spider plant produces new cells in the runner by a process

called .......................................................................................................................... (1)

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(e) This type of reproduction is called ...................................................... reproduction. (1)

(Total 5 marks)

Q4. Diagram 1 shows the nucleus of a body cell as it begins to divide by mitosis.

Diagram 1

(a) Use a word from the box to label Diagram 1.

(1)

alleles chromosomes gametes

(b) Complete Diagram 2 to show what the nucleus of one of the cells produced by this mitosis would look like.

Diagram 2

(1)

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(c) Stem cells from a recently dead embryo can be grown in special solutions.

Some facts about stem cells are given below.

• Stem cells from an embryo can grow into any type of tissue.

• Stem cells may grow out of control, to form cancers.

• Large numbers of stem cells can be grown in the laboratory.

• Stem cells may be used in medical research or to treat some human diseases.

• Patients treated with stem cells need to take drugs for the rest of their life to prevent rejection.

• Collecting and growing stem cells is expensive.

Use only the information above to answer these questions.

(i) Give two advantages of using stem cells.

1 ........................................................................................................................

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2 ........................................................................................................................

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(ii) Give two disadvantages of using stem cells.

1 ........................................................................................................................

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2 ........................................................................................................................

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(Total 6 marks)

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Q5. The diagram shows a family tree in which some individuals have an inherited disorder, which may cause serious long-term health problems.

(a) What proportion of the children of A and B have the disorder?

..................................................................................................................................... (1)

(b) Explain the evidence from the diagram which shows that the allele for the disorder is dominant.

Use the appropriate letters to identify individuals in your answer.

You may use genetic diagrams in your explanation. There is space for you to draw a genetic diagram at the top of the facing page.

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(c) (i) What is meant by ‘embryo screening’?

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(ii) A doctor suggests that couple C and D should have their embryos screened but that couple G and H do not need this procedure.

Explain the reasons for the doctor’s suggestions.

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(Total 8 marks)

Q6. A woman gives birth to triplets. Two of the triplets are boys and the third is a girl. The triplets developed from two egg cells released from the ovary at the same time.

The diagram shows how triplets A, B and C developed.

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(a) Which stages on the diagram show gametes?


1 and 2 2 and 3 3 and 7 1 and 7 (1)

(b) Embryo B is male.

Which of the following explains why embryo B is male?

Tick ( ) one box.

Cell P has an X chromosome; cell R has an X chromosome.

Cell P has a Y chromosome; cell R has an X chromosome.

Cell P has an X chromosome; cell R has a Y chromosome. (1)

(c) The children that develop from embryos A and C will not be identical.

Explain why.

You may use words from the box in your answer.

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egg genes sperm

(d) Single cells from an embryo at Stage 7 can be separated and grown in a special solution.

(i) What term describes cells that are grown in this way?


lleles screened cells stem cells (1)

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(ii) What happens when the cells are placed in the special solution?

Tick ( ) two boxes.

The cells divide

The cells fertilise

The cells differentiate

The cells separate (2)

(iii) Give one use of cells grown in this way.

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(iv) Some people might object to using cells from embryos in this way.

Give one reason why.

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(Total 9 marks)

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Q7. DNA fingerprinting can be used to identify people. One example of the use of DNA fingerprinting is to find out which man is the father of a child. The diagram shows the DNA fingerprints of a child, the child’s mother and two men who claim to be the child’s father. The numbers refer to the bars on the DNA fingerprints.

(a) Only half the bars of the child’s DNA fingerprint match the mother’s DNA fingerprint. Explain why.

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........................................................................................................................ (2)

(b) Which man, A or B, is more likely to be the father of the child?

Use the numbers on the DNA fingerprints to explain your choice. In your answer you should refer to all four people.

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(Total 5 marks)

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Q8. Sometimes babies are born with extra fingers or toes as shown in the photograph.

This condition is called polydactyly.

©CNRI / SCIENCE PHOTO LIBRARY

The diagram shows the inheritance of polydactyly in a family.

(a) Polydactyly is caused by a dominant allele, D. The recessive allele of the gene is represented by d.

Use one genetic diagram to show the inheritance of the polydactyly gene by R and S.

(4)

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(b) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.

Embryos can be screened for genetic disorders.

Many people would favour the use of embryo screening for cystic fibrosis but not for polydactyly.

Compare the issues involved in the use of embryo screening for cystic fibrosis and for polydactyly. You should use your knowledge and understanding of the process and the two conditions.

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(Total 10 marks)

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Q9. The diagram shows one way that stem cells can be produced from human embryos.

Sue Medaris/University of Wisconsin-Madison

(a) Stem cells can be used to treat a condition such as paralysis.

Explain why.

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(b) During pregnancy, an umbilical cord and a placenta join the embryo to the mother. At birth the umbilical cord is cut.

Stem cells can be obtained from the umbilical cord.

Many people think that the stem cells for treating human conditions should be obtained from umbilical cords rather than human embryos.

Suggest one reason why.

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(c) Stem cells divide by mitosis. Gametes are formed by meiosis.

Give two differences between mitosis and meiosis.

1 .....................................................................................................................

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(Total 5 marks)

Q10. The diagram shows how cells from human embryos can be used to grow ‘replacement body parts’ for humans.

Sue Medaris/University of Wisconsin-Madison

(a) Complete the following sentences.

(i) The fertilised egg has ................................. sets of genetic information. (1)

(ii) The fertilised egg divides to form the 5-day-old embryo by a process

called ................................................................ (1)

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(b) Some statements about stem cells are given below.

Tick ( ) two advantages and two disadvantages of using stem cells to grow ‘replacement body parts’ for humans.

(4) (Total 6 marks)

Advantage Tick ( )

Disadvantage Tick ( )

Stem cells can grow into many different kinds of body cells.

Stem cells may grow out of control.

Large numbers of stem cells can be grown in the laboratory.

Stem cells may be used to treat some human diseases.

Collecting and growing stem cells is expensive.

Patients treated with stem cells may need to take drugs for the rest of their life to prevent rejection.

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M1. (a) cell membranes 1

(b) (i) two recessive / cystic fibrosis / faulty / diseased / the allele(s) / genes two can be implied by second marking point ignore chromosomes

1

from Bob and Carol / both parents / the parents

if no other marks awarded ‘Carol is a carrier’ gains 1 mark 1

(ii) (inherited) dominant / normal allele / gene 1

from Carol / mother ignore references to recessive allele / gene from father / Bob if no other marks awarded he has just / only one recessive allele gains 1 mark

1

(c) (i) reduce number of people with cystic fibrosis (in population)

or

reduce health-care costs

or

expensive to have baby with cystic fibrosis accept to allow decision / emotional argument qualified eg allows abortion or allows people to make choices about termination or help to prepare financially / emotionally etc

1

(ii) any one from:

• possible damage / risk to embryo / fetus / baby allow possible harm / risk to mother

• screening / it is expensive

• (may) have to make ethical / moral / religious decisions ignore not natural / playing God / unethical / immoral / religious unqualified

• right to life 1

[7]

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M2. (a) any two from:

accept other logical / reasonable ideas

• other scientists not aware of his work

• chromosomes / DNA / genes not seen / discovered / known do not accept there was no interest in genetics

• other theories accepted at the time

• not considered to be a scientist / not eminent / respected allow ‘he was just / only a monk’

2

(b) (i) random selection accept a method of achieving random selection eg “take a handful” if number given, minimum 20

1

(ii) any one from:

• 1:1 / one to one

• 19:21 accept any ratio to give correct answer, eg “50:50” do not accept 21:19 unqualified

1

(iii) A + a as gametes from 1st parent

1

a + a as gametes from 2nd parent allow a alone

1

(offspring / 2nd generation) Aa aa

offspring must be derived from correct gametes

correct identification of yellow (Aa) other symbols correctly used can gain full marks

1

or

green (aa) (if both given, both must be correct) ignore references to previous generations if no other marks awarded, both correct parental genotypes given gains 1 mark

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examples of award of first three marks

1

[8]

M3. (a) characteristics 1

(b) genes 1

(c) chromosomes 1

(d) mitosis 1

(e) asexual 1

[5]

-

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M4. (a) chromosomes 1

(b) diagram showing four separate chromosomes two long and two short (as in diagram 1)

allow each chromosome shown as two joined chromatids do not allow if chromosomes touching each other

1

(c) (i) any two from:

• can grow into any type of tissue / named tissue

• used in medical research

• used to treat human diseases

• large numbers can be grown 2

(ii) any two from:

• expensive

• grow out of control / ref cancers

• may be rejected

• need for drugs (for rest of life) 2

[6]

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M5. (a) 1 in 4 / 1/4 / 1: 3 / 25% / 0.25

do not accept 3:1 / 1:4 / 2:6 1

(b) either from C and D

accept synonyms for dominant / recessive eg Normal / faulty accept genetic diagram if clearly referring to correct individuals or genotypes on family tree allow ‘gene’ for ‘allele’

any three from:

• C and D have disorder

ignore ‘C & D are carriers’

• I/J don’t have disorder

• C and D have dominant and recessive alleles

• recessive alleles from C and D passed to I/J or I/J have two recessive alleles

NB if allele was recessive then all offspring of C and D would have the disorder = 3 marks

or from A and B

assume response refers to A + B unless contradicted

• A is homozygous recessive / rr, and B is heterozygous / Rr can be shown in words or symbols

allow any symbol

• offspring can be rr or Rr described

allow without key 3

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(c) (i) (embryos) checked for inherited / genetic disorders / conditions accept diseases for disorders

1

(ii) any three from:

• C/D have disorder / have dominant allele accept disease / condition accept ‘gene’ for ‘allele’ ignore reference to ‘carriers’

• chance of embryo / foetus / child having disorder or may pass on alleles for disorder to their offspring

• C/D might want to decide on termination or prepare for child with disorder

• G and H don.t have disorder / both homozygous recessive / have no dominant alleles (for this disorder)

• so offspring (of G and H) cannot / don.t have disorder 3

[8]

M6. (a) 2 and 3 1

(b) cell P has an X chromosome; cell R has a Y chromosome 1

(c) any two from:

• (formed from) different egg / 2 eggs

• (formed from) different sperm / 2 sperm

• have different genes / alleles / chromosomes / DNA allow genetics

2

(d) (i) stem cells 1

(ii) the cells divide 1

the cells differentiate 1

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(iii) (medical) research / named eg growing organs or

medical / patient treatment allow (embryo) cloning do not allow designer babies / more babies

1

(iv) any one from:

• ethical / moral / religious objections ignore cruel / not natural / playing God

• potential harm to embryo allow deformed ignore harm to mother

1 [9]

M7. (a) eggs produced by meiosis 1

therefore contain only half of mother’s DNA 1

(b) (man B) no marks

(child has) mother’s 25 / 28 / 30 / 31 or child gets 17 / 19 / 22 / 24 from mother

1

(child has) man B’s 10 / 12 / 13 / 14 or child gets 18 / 20 / 21 / 23 from B

1

no bars / DNA / lines from man A correspond to child 1

[5]

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M8. (a) (genotype / gametes from P / father) D and d (*) 1

(genotype / gametes from Q / mother) d and d / accept d(*) 1

offspring genotypes correctly derived from correct gametes(*) 1

offspring phenotypes R and S identified 1

(*) eg may be in punnett square allow own upper and lower case symbols or allow any symbol correctly used with key

(b) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response.

No relevant content. 0 marks

There is a brief description of the issues involved in screening for at least one condition.

Level 1 (1–2 marks)

There is some description of issues involved in screening for both conditions but there is a lack of both pros and cons for the two conditions.


There is a clear, balanced and detailed description of the issues involved in screening for both conditions, giving pros and cons for each condition.


examples of biology points made in the response

For cystic fibrosis

pros:

• reduce number of people with cystic fibrosis (in population)

• reduce health-care costs

• allows decision / emotional argument, eg allows people to make choices about termination

cons:

• possible damage / risk to embryo / fetus / baby

• possible harm / risk to mother

• (may) have to make ethical / moral / religious decisions

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for polydactyly:

• cures ‘disfigurement’

• but condition not life threatening

• so risks to foetus / mother unjustified [10]

M9. (a) because stem cells can (be made) to differentiate 1

into nerve / muscle cells 1

(b) ethical issues with destruction / damage to embryo 1

(c) mitosis one cell division, meiosis two cell division 1

cells produced by mitosis have two sets of chromosomes, cells produced by meiosis have one set of chromosomes

accept cells produced by mitosis are genetically identical, cells produced by meiosis have some genetic differences

1 [5]

M10. (a) (i) two 1

(ii) mitosis 1

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(b)

1 mark for each correctly ticked advantage up to a maximum of 2 marks 1 mark for each correctly ticked disadvantage up to a maximum of 2 marks deduct 1 mark each for every incorrect box ticked in each column up to a maximum of 2 deductions in each column

4 [6]

Adv. Disadv.

Stem cells can grow into many different kinds of body cells.

Stem cells may grow out of control.

Large numbers of stem cells can be grown in the laboratory.

Stem cells may be used to treat some human diseases.

Collecting and growing stem cells is expensive.

Patients treated with stem cells need to take drugs for the rest of their life to prevent rejection.

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Cell Division and Inheritance Revision 3 · (c)€€€€ Bob and Carol know that there is a risk...

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