Meiosis

New cells are produced by cell division.

Figure 5 shows sperm formation in a human.

Where in the body are sperm cells produced?

How many chromosomes are there in cell A and in cell D ?

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Complete the sentence.

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Strawberry plants can reproduce both sexually and asexually.

Figure 6 shows a strawberry plant reproducing:

• sexually, using flowers, fruits and seeds

• asexually, using horizontal stems called runners.

Meiosis produces gametes.

What is the name of the male gamete in a flower?

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Which process produces new cells in runners?

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Substances used for growth pass through the runners from the parent plant to the offspring plants.

Which two substances pass through the runners?

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Sexual reproduction and asexual reproduction each have different advantages for the strawberry plant.

Give one advantage of reproducing sexually.

Give one advantage of reproducing asexually.

New cells are produced by cell division.

Figure 5 shows sperm formation in a human.

Which cell division in Figure 5 represents mitosis?

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Which two cells in Figure 5 are genetically identical?

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How many chromosomes are there in cell J in Figure 5 ?

How many of the cells C, D, E, F, G, H, I and J contain a Y chromosome?

Use Figure 5.

Strawberry plants can reproduce both sexually and asexually.

Figure 6 shows a strawberry plant reproducing:

• sexually using flowers, fruits and seeds

• asexually using horizontal stems called runners.

Explain why the offspring produced using runners are genetically identical.

Explain why the offspring produced using flowers, fruits and seeds are not genetically identical.

Describe two advantages of asexual reproduction for the survival of strawberry plants.

Describe two advantages of sexual reproduction for the survival of strawberry plants.

Figure 13 shows six stages in the process of meiosis.

In Figure 13, A is the first stage and F is the final stage. Stages B to E are not in the correct order. Give the correct order of stages A to F.

At the end of meiosis the number of chromosomes is different from the number of chromosomes at the start of meiosis.

Give the number of chromosomes in one cell in Figure 13:

• at the start of meiosis

• at the end of meiosis.

Explain why the change in the number of chromosomes is important.

Meiosis produces cells that are genetically different. Describe how meiosis produces cells that are genetically different.

Chromosomes contain DNA. Figure 14 shows part of a DNA molecule.

What type of substances are labelled A, C, G and T in Figure 14 ?

DNA is made of nucleotides. How many nucleotides are shown in Figure 14 ?

There are two types of reproduction:

• sexual reproduction

• asexual reproduction.

Complete Table 4 to compare sexual reproduction with asexual reproduction.

The first row has been completed for you.

Gametes are formed in sexual reproduction. Name the male gamete formed in flowering plants.

Cell division by meiosis forms gametes. Figure 12 shows the mean mass of DNA per cell before, during and after meiosis.

Use information from Figure 12 to answer questions 08.3 to 08.6.

When is the DNA in the chromosomes being copied? Tick (✓) one box.

Cells divide twice during meiosis. Which two times in Figure 12 show one cell dividing into two cells? Tick (✓) two boxes.

What is the mean mass of DNA in arbitrary units in a sperm cell? Tick (✓) one box.

What is the mean mass of DNA in arbitrary units in each cell in an embryo? Tick (✓) one box.

There are two types of reproduction:

• sexual reproduction

• asexual reproduction.

Complete Table 1 to compare sexual reproduction with asexual reproduction.

The first row has been completed for you.

Gametes are formed in sexual reproduction. Name the male gamete formed in flowering plants.

Cell division by meiosis forms gametes. Figure 1 shows the mean mass of DNA per cell before, during and after meiosis.

Use information from Figure 1 to answer questions 01.3 to 01.6.

When is the DNA in the chromosomes being copied? Tick (✓) one box.

Cells divide twice during meiosis. Which two times in Figure 1 show one cell dividing into two cells? Tick (✓) two boxes.

What is the mean mass of DNA in arbitrary units in a sperm cell? Tick (✓) one box.

What is the mean mass of DNA in arbitrary units in each cell in an embryo? Tick (✓) one box.

The nucleus of a cell contains DNA.

Name the structures inside the cell nucleus that contain DNA.

Figure 13 shows part of a DNA molecule.

Name the part of the DNA molecule labelled X.

What type of substances are labelled A, C, G and T in Figure 13 ?

Figure 14 shows another section of a DNA molecule.

Four of the substances you named in Question 08.3 are not labelled in part Y of Figure 14. Label each of these substances with the correct letter, A, C, G or T. Use information from other parts of Figure 14 to help you.

What is happening to the DNA in part Z of Figure 14 ?

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A gene is a length of DNA. What type of substance does a gene code for?

Most human body cells contain 6 10^–12 grams of DNA. What mass of DNA will a human sperm cell contain?

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What is the name of the type of cell division that produces sperm cells?

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The nucleus of a cell contains DNA.

Name the structures inside the cell nucleus that contain DNA.

Figure 1 shows part of a DNA molecule.

Name the part of the DNA molecule labelled X.

What type of substances are labelled A, C, G and T in Figure 1 ?

Figure 2 shows another section of a DNA molecule.

Four of the substances you named in Question 01.3 are not labelled in part Y of Figure 2. Label each of these substances with the correct letter, A, C, G or T. Use information from other parts of Figure 2 to help you.

What is happening to the DNA in part Z of Figure 2 ? Tick (✓) one box.

A gene is a length of DNA. What type of substance does a gene code for?

Most human body cells contain 6 10^–12 grams of DNA. What mass of DNA will a human sperm cell contain? Tick (✓) one box.

What is the name of the type of cell division that produces sperm cells? Tick (✓) one box.

Sperm cells and egg cells are formed by meiosis.

During meiosis a cell divides twice.

How many sperm cells are formed when a cell divides by meiosis?

Human body cells contain 46 chromosomes.

How many chromosomes are in each human egg cell?

Dupuytren’s is a disorder that affects the hands.

One form of Dupuytren’s is caused by a dominant allele (D).

The allele for not having Dupuytren’s is recessive (d).

What is an allele?

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A man with Dupuytren’s has the genotype Dd.

Which word describes the man’s genotype?

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The man with Dupuytren’s (Dd) and a woman who does not have Dupuytren’s (dd) plan to have a child.

Complete the genetic diagram in Figure 4 to show the possible genotypes of the child.

Draw a ring around the genotype of a child in Figure 4 who will have Dupuytren’s.

What is the chance of the child having Dupuytren’s?

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A genetic disorder develops as a result of a change in a gene.

What scientific term describes a change in a gene?

People with a family history of some genetic disorders are offered embryo screening.

Suggest one way embryo screening can help people with a family history of a genetic disorder.

Figure 6 shows the production of sperm cells in humans.

Cell A is a normal body cell.

How many chromosomes are there in cell A ?

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What is the mass of DNA in cell E ?

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What type of cell division produces sperm cells?

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Sometimes there are errors in copying the genetic material.

What term describes an error in the genetic material?

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A woman has three children, aged 4, 6 and 9 years.

Why are the children not genetically identical?

In sexual reproduction, a sperm cell fuses with an egg cell to form a new single cell.

An embryo develops from the single cell.

The cell divides three times to produce the embryo.

How many cells are there in the embryo after three cell divisions?

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Figure 7 shows a different human embryo.

Measure image length X on Figure 7.

Give your answer in millimetres (mm).

The image in Figure 7 has been magnified 500

Calculate the real length of the embryo.

Use the equation:

Give your answer in micrometres (m).

The embryo may not implant in the lining of the uterus.

The embryo will then be lost from the woman’s body several days later.

Explain why the woman may not notice this has happened.