B1 - You And Your Genes

Question 1

Give an example of a human characteristic determined only by genes

Answer 1

Eye colour, natural hair colour, blood group, dimples

Question 2

Is height affected by genes, environmental factors, or both? Explain your answer

Answer 2

Height is controlled by both genes and environmental factors. For example if your parents are both tall then you’re likely to be tall. However, if you grow up in a place with a food shortage, you’ll be shorter than if you had all the food you needed.

Question 3

Give an example of a human characteristic that is affected by the environment

Answer 3

Weight, height, skin colour, condition of teeth, academic or athletic ability

Question 4

What is in the nucleus?

Answer 4

The ucleus contains genetic material. The genetic material in the nucleus is arranged in to chromosomes. The human cell nucleus contains 23 pairs of chromosomes. Each chromosome is one very long molecule of DNA that is coiled up. A gene is a short length of a chromosome. Genes control the development of different characteristics, for example hair colour and how an organism functions.

Question 5

What are alleles?

Answer 5

Alleles are different versions of the same gene

Question 6

What do genes code for?

Answer 6

Genes code for proteins. Proteins are the building blocks of cells. Having different versions of proteins means that we end up with different characteristics.

Question 7

What is an organism’s genotype?

Answer 7

An organisms genotype is all of the genes it has

Question 8

What is an organism’s phenotype?

Answer 8

The characteristics or physical features that an organism displays

Question 9

Why are children never identical to one of their parents?

Answer 9

Children inherit half their chromosomes from their mother and half from their father. This means that they don’t get all of the same alleles as one of the parents, so they won’t look identical to them.

Question 10

In terms of genes, why do people naturally have different coloured hair?

Answer 10

You can get different versions of the same gene, which give different versions of a particular characteristic. These different versions of genes are called alleles. There are different alleles of the gene for hair colour. The alleles that you have will determine your hair colour.

Question 11

How does sexual reproduction in humans work, and how does it produce variation?

Answer 11

During sexual reproduction a sperm cell fertilises an egg cell. The fertilised egg cell contains a mixture of chromosomes - half from the mother, and half from the father. This means the offspring inherits a combination of alleles (and therefore features) from each parent, producing variation.

Question 12

How is the number of chromosomes in a sex cell different from the number of chromosomes in a body cell?

Answer 12

Body cells contain 46 chromosomes - 23 pairs. Sex cells contain 23 chromosomes.

Question 13

The allele for being a werewolf is recessive (w). Remus is a werewolf. What is his genotype? Explain why

Answer 13

For a recessive characteristic to show an individual must have both recessive allele is. This means we must must have to recessive werewolf alleles (ww). If he only had one recessive werewolf allele then the dominant allele ‘non-werewolf’ characteristic would be displayed.

Question 14

Why do children often resemble their parents?

Answer 14

Children inherit half their chromosomes from their mother and half from the father. This means that they get some alleles from each parent, so will display some characteristics from each parent, for example a child may have their mum’s big nose, and their dad’s little ears.

Question 15

Pink hair (H) is dominant over green hair (h) in giraffes. What colour hair would a giraffe with the genotype Hh have? Explain why

Answer 15

The giraffe will have pink hair, as the pink hair allele (H) is dominant over the recessive green hair allele (h).

Question 16

What do the terms genotype and phenotype mean?

Answer 16

Genotype means what combination of alleles you have. Phenotype means the characteristic (physical feature) you display as a result of your genotype.

Question 17

Define homozygous and heterozygous

Answer 17

Homozygous means you have two of the same alleles for that particular gene. Heterozygous means you have two different alleles for that particular gene.

Question 18

Proteins can be structural or functional give an example of each type

Answer 18

Collagen is a structural protein. The enzyme amylase is a functional protein.

Question 19

How does the presence of a Y chromosome cause an embryo to develop testes?

Answer 19

The Y chromosome (which is only present in males) carries a gene which causes a specific protein to be produced. This protein causes the testes to develop in an embryo. In the absence of this protein (no Y chromosome) the embryo develops ovaries.

Question 20

Alex has an X chromosome and a Y chromosome. Is Alex a boy or a girl?

Answer 20

Alex is a boy. The Y chromosome causes male characteristics.

Question 20

What symptoms will someone suffering from Huntington’s disease experience?

Answer 20

Having tremors, clumsiness, memory loss, inability to concentrate and mood changes.

Question 21

Is the gene for Huntington’s disease dominant or recessive? Explain what your answer means in terms of inheritance of the disorder.

Answer 21

It’s dominant. The disorder can be inherited if just one parent carries the gene. (If the disorder was recessive both parents would need to have the faulty allele for there to be a risk of the child inheriting the condition). If a parent is a carrier, they are also a sufferer.

Question 22

What symptoms will someone suffering from cystic fibrosis experience?

Answer 22

Difficulty breathing, producing a thick mucus, chest infections and difficulty digesting food.

Question 23

What is the risk of carrying out a genetic test during pregnancy?

Answer 23

Genetic testing can increase the chance of miscarriage during pregnancy.

Question 24

What is pre-implantation genetic diagnosis?

Answer 24

This is where embryos produced by IVF are tested for genetic disorders before being implanted into the mothers womb.

Question 25

Describe the concerns genetic testing brings up for the people and families involved.

Answer 25

• Genetic testing increases the chance of miscarriage.
• Using results from genetic tests that may not be accurate can lead to a person making important life decisions based on incorrect information.
• Genetic testing can affect a person’s decision on whether to have children.
• Genetic testing can affect a person’s decision on whether to terminate a pregnancy.
• If a person finds out that they have a genetic disorder, they have to make a decision on whether to inform other family members.

Question 26

Why might a person have genetic testing?

Answer 26

• To see if they carry the genes for a genetic disease

- To see if they might benefit from a certain drug

Question 27

What is a false positive result?

Answer 27

When a person gets told that they have the genetic disorder when they don’t. This could lead to abortion based which would be a decision based on incorrect results.

Question 28

What is a false negative result?

Answer 28

When someone gets told they don’t have the genetic disorder when they do have it.

Question 30

What are clones?

Answer 30

Clones are genetically identical organisms

Question 32

Why are some people worried about employers or insurance companies getting hold of genetic test results?

Answer 32

• Employers might discriminate against people with genetic disorders by refusing to employ them as they are likely to get ill
• Insurance companies might refuse insurance to people with the genetic disorders

Question 34

Describe how a scientist can make an animal clone in a lab.

Answer 34

The scientist removes the nucleus of an unfertilised egg cell, and replaces it with the nucleus of an adult donor cell. The cell is then stimulated so it starts dividing and an embryo that is genetically identical to the donor cell is produced.

Question 35

How do plants reproduce asexually to form clones?

Answer 35

Some plants produce runners that form clones of the parent plant at the tips. Other plants produce bulbs that grow to form a plant identical to the parent.

Question 36

Identical twins are a type of clone. How are they formed?

Answer 36

A single egg fertilised by a sperm begins to develop into an embryo as normal, but then splits. To genetically identical embryos then develop and are born as genetically identical babies.

Question 37

What illnesses are adult stem cells used to treat?

Answer 37

Blood diseases, for example sickle cell anaemia, can be treated through bone marrow transplants. Bone marrow contains adult stem cells that can turn into new blood cells to replace the faulty old ones.

Question 38

How can embryonic stem cells be used to help people with illnesses?

Answer 38

Embryonic stem cells could be used to make beating heart muscle cells for people with heart disease, insulin producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries, and so on.

Question 39

A liver cell is specialised for detoxification. Has this cell always been specialised? Explain your answer.

Answer 39

No. Most cells in our body start off as unspecialised cells called stem cells. During early development they become specialised to do a particular job, for example detoxification.

Question 40

What are embryonic stem cells and why are they exciting to doctors and researchers?

Answer 40

Embryonic stem cells are unspecialised cells found in the early embryo, which have the potential to become any type of cell. They are exciting to doctors and researchers as they could, in theory, be used to replace faulty cells in people with illnesses.

Question 41

What are the differences between adult stem cells and embryonic stem cells?

Answer 41

Embryonic stem cells are unspecialised cells found in the early embryo, which have the potential to become any type of cell. Adult stem cells are also unspecialised cells, but they are found in adult animals. They are able to specialise in to many, but not all, types of cell.