IB Biology SL 3.3 Meiosis Name:

3.3 Meiosis

Essential idea: Alleles segregate during meiosis allowing new combinations to be formed by the fusion of gametes.

Nature of Science: Making careful observations—meiosis was discovered by microscope examination of dividing germ-line cells.

Statement Guidance3.3 U1 One diploid nucleus divides by meiosis to produce four haploid

nuclei.3.3 U2 The halving of the chromosome number allows a sexual life cycle

with fusion of gametes.3.3 U3 DNA is replicated before meiosis so that all chromosomes consist of

two sister chromatids.3.3 U4 The early stages of meiosis involve pairing of homologous

chromosomes and crossing over followed by condensation.3.3 U5 Orientation of pairs of homologous chromosomes prior to separation

is random.3.3 U6 Separation of pairs of homologous chromosomes in the first division

of meiosis halves the chromosome number.3.3 U7 Crossing over and random orientation promotes genetic variation. The process of

chiasmata formation need not be explained.

3.3 U8 Fusion of gametes from different parents promotes genetic variation.3.3 A1 Application: Non-disjunction can cause Down syndrome and other

chromosome abnormalities.3.3 A2 Application: Studies showing age of parents influences chances of

nondisjunction.3.3 A3 Application: Description of methods used to obtain cells for

karyotype analysis e.g. chorionic villus sampling and amniocentesis and the associated risks.

3.3 S1 Skill: Drawing diagrams to show the stages of meiosis resulting in the formation of four haploid cells.

Drawings of the stages of meiosis do not need to include chiasmata.

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IB Biology SL 3.3 Meiosis Name:

1.

Define haploid:

Define diploid:

Define crossing over:

Crossing over is the exchange of genetic material between two homologous chromosomes which have paired up during Prophase I. The result ofcrossing over is genetic recombination: an exchange of genes.

2. Meiosis starts with one cell. State how many cells result from meiosis.

What are those cells called?

3. State the number of chromosomes

a. - in a diploid human cell.

b. -in a haploid human cell.

4. State what is meant by a reduction division of a diploid nucleus?

5. Define the following:Homologous chromosomes

Sister chromatids

Centromere

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IB Biology SL 3.3 Meiosis Name:

6. Draw and annotate the stages of meiosis.

7. Distinguish between mitosis and meiosis.

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IB Biology SL 3.3 Meiosis Name:

Tip- when asked to distinguish, make a table so that each row outlines the differences in one feature of the items being outlined.

Mitosis Meiosis

Results in 2 daughter cells Results in 4 daughter cells

8. What is random orientation and when does it occur in meiosis?

9. Explain how meiosis leads to variation. (6 marks) Tip: When asked to explain, you should always remember to define any key terms & provide named examples. You need to give many details about how and why things are. This question is worth 6 marks- that means you need to include at least 6 details relating meiosis to variation in your explanation.

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IB Biology SL 3.3 Meiosis Name:

10. Draw a labelled diagram of the human life cycle. Use the terms diploid, haploid, gametes, sperm, ovum, fertilization, zygote, adult, & meiosis.

11. What is trisomy?

12. Disjunction is the separation of chromosomes. Outline what happens during non-disjunction & state when it can occur.

13. Explain how non-disjunction can result in Down syndrome. (Use bullet points- it can help)

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IB Biology SL 3.3 Meiosis Name:

14. Outline how a karyograph is made.

15. Analyze the following karyographs.

non-disjunction yes / no Gender? 2) non-disjunction yes / no Gender?

16.

Define prenatal:

Define diagnose:

Define abnormality:

Define fetus:

State the name of the protective liquid surrounding a fetus.

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(from www.intropsych.com)

IB Biology SL 3.3 Meiosis Name:

17. Describe the process of chorionic villus sampling and the associated risks.

18. Describe the process of amniocentesis and the associated risks.

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IB Biology SL 3.3 Meiosis Name:

Use the following graph for questions 19-21.

19. Calculate the change in the risk of down syndrome between ages 30 and 40.Tip: When asked to calculate, you need to show your working and state units.

20. Outline the relationship between maternal age and risk of Down syndrome.

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From: http://courses.lumenlearning.net/biology/wp-content/uploads/sites/5/2014/02/Figure_07_03_03.jpg