B1 - You And Your Genes

Question 1

How many chromosomes are there in a gamete?

Answer 1

23 chromosomes

Question 2

What is an allele?

Answer 2

A variation of the same type of gene.

Question 3

Where are chromosomes found within a cell?

Answer 3

In the nucleus

Question 4

True or false - in humans, chromosomes are usually found in groups of four?

Answer 4

False - they are found in pairs

Question 5

How do genes control the different characteristics we develop?

Answer 5

They code for the proteins which structure our features and therefore the characteristics we display

Question 6

What do the words ‘genotype’ and ‘phenotype’ mean?

Answer 6

Genotype = All of the genes in an organism
Phenotype = The genes the organism displays

Question 7

Is a person’s weight determined by genes, the environment or a combination of both?

Answer 7

Both

Question 8

Name the two types of sex cell.

Answer 8

Egg cells and sperm cells

Question 9

How many chromosomes are found in sex cells? And what are these cels called?

Answer 9

23 chromosomes

Gametes

Question 10

Why do most children look a bit like both of their parents but not identical to either?

Answer 10

Because you receive half of your genes from both parents

Question 11

What is the difference between homozygous and heterozygous?

Answer 11

Homozygous = both your alleles for that particular gene are the same e.g. AA
Heterozygous = your alleles for that particular gene are different e.g. Aa

Question 12

What sex chromosomes do human males have?

Answer 12

X and Y

Question 13

How does a gene on one of the human sex chromosomes cause embryos to develop into males?

Answer 13

Because it codes for the protein which develops the testes and the rest of the male reproductive system.

Question 14

Is the allele for cystic fibrosis dominant or recessive?

Answer 14

Recessive

Question 15

What are the symptoms of cystic fibrosis?

Answer 15

• thick, sticky mucus
• difficulty breathing
• difficulty digesting food = often small and skinny
• chest infections =painful coughing

Question 16

What are the symptoms of Huntington’s disease?

Answer 16

• Clumsiness
• Memory loss
• Poor concentration
• Mood changes
• Tremors (shaking)

Question 17

What is the chance of a child inheriting Huntington’s disease if one of their parents has one copy of the faulty allele?

Answer 17

50%

Question 18

During IVF treatment, what is the process of testing embryos to see if they have a genetic disorder called?

Answer 18

Pre-implantation genetic diagnosis

Question 19

Other than testing embryos during IVF, give other uses of genetic testing.

Answer 19

• To check if you have a condition before antibiotics are prescribed to you and prevent adverse reactions
• Children and adults can be checked to see if they carry alleles for genetic disorders.

Question 20

What happens to an embryo in IVF treatment of it carries a genetic disorder?

Answer 20

It is discarded.

Question 21

Describe three issues surrounding genetic testing.

Answer 21

1- That all of the embryos have equal rights to life and should not be discarded
2- If someone in the family has a genetic disorder should all their relatives be tested?
3- If someone has a genetic disorder is it right for them to have children?

Question 22

Write a definition of the word ‘clone’.

Answer 22

A clone is an organism with identical DNA to another.

They have the same genes and the same alleles of those genes.

Question 23

How can bacteria reproduce asexually?

Answer 23

Their cells duplicate, doubling the population each time.

Question 24

How can plants reproduce asexually?

Answer 24

Some plants produce horizontal stems called runners that move out from the base of the plant and form new clones at their tips e.g strawberry plants
Other plants produce underground fleshy structures called bulbs. These can then grow to form a new identical plant e.g garlic

Question 25

How can animals reproduce asexually?

Answer 25

Some animals can lay eggs that are already fertilised and then become identically organisms e.g female greenfly
Female greenfly’s can also reproduce sexually when they feel like it

Question 26

How are identical twins formed?

Answer 26

Identical twins are also clones. One egg is fertilised by sperm and starts to develop. The embryo then splits in 2 and they begin to develop separately. These 2 embryos are still genetically identical.

Question 27

What are stem cells?

Answer 27

Unspecialised cells - they can develop into different types of cells depending on what ‘instructions’ they are given

Question 28

What are the two main types of stem cells and what are their differences?

Answer 28

Embryonic Stem Cells - found in early embryos, the stem cells are removed and then the embryo is destroyed. They can turn into ANY cell.
Adult Stem Cells - found in adult animals and can maintain and repair old and damaged tissues. CANNOT turn into any cell type. No embryos have to be destroyed as they can be removed from the bone marrow of the animal

Question 29

Describe ways in which stem cells could be used to treat an illness.

Answer 29

Embryonic Stem Cells - replace faulty cells such as creating a new heart muscle for those with heart disease, insulin-producing cells for those with diabetes and nerve cells for those paralysed by spinal injuries.
Adult Stem Cells - cure diseases such as those with blood diseases can have bone marrow transplants as the stem cells can turn into new blood cells and replace the faulty ones.