Genetics

Question 1

What is the structure of DNA?

Answer 1

Deoxyribonucleic acid is a double stranded, double helix molecule

Question 2

Where in the cell is DNA found?

Answer 2

Deoxyribonucleic acid is found in the nucleus of a cell. It is arranged wound up in Chromosomes.

Question 3

What is a gene?

Answer 3

A gene is a section of a Chromosome that codes for a particular trait/characteristic e.g. hair colour.

Question 4

What is an allele?

Answer 4

An allele is an alternative form of a gene e.g. if the gene is eye colour an allele may be blue eyes, green eyes.

Question 5

What can cause variation within a species?

Answer 5

Genetic and environmental factors

Question 6

What is a dominant allele?

Answer 6

An allele that will always be expressed

Question 7

What is a recessive allele?

Answer 7

An allele that will need to be in a homozygous pair to be expressed

Question 8

How are recessive and dominant alleles written?

Answer 8

A dominant allele is always a capital letter while a recessive allele is always the corresponding smaller letter

Question 9

What is the genotype?

Answer 9

The allele pair for each characteristic

Question 10

What is the phenotype?

Answer 10

The physical expression of an allele pair

Question 11

How many chromosomes do humans have?

Answer 11

Humans have 23 pairs of chromosomes in each cell

Question 12

How many chromosomes does each gamete (sex cell) have?

Answer 12

The human egg and sperm cell contain 23 chromosomes each.

Question 13

What is the name of the cell created after fertilisation?

Answer 13

A zygote

Question 14

What is cystic fibrosis?

Answer 14

An inherited disease that affects the respiratory system and digestive system. Sufferers produce much more, thicker mucus which lines the respiratory system.

Question 15

What is cystic fibrosis?

Answer 15

An inherited disease that affects the respiratory system and digestive system. Sufferers produce much more, thicker mucus which lines the respiratory system.

Question 16

Is Cystic Fibrosis caused by a dominant or recessive allele?

Answer 16

Cystic Fibrosis is caused by a recessive allele

Question 17

What is a clone?

Answer 17

A genetically identical organism

Question 18

What (naturally) creates clones?

Answer 18

Asexual reproduction

Question 19

How can plants be cloned?

Answer 19

By taking a cutting of the plant

Question 20

How was Dolly the sheep cloned?

Answer 20

• Cell was taken from the udder of a Finn-Dorset sheep
• An egg was taken from a Scottish Blackface sheep and it’s nucleus was removed.
• the two cells were combined with an electric shock
• the combined cell now has a single nucleus from the nuclear donor (Finn Dorset)
• Egg divides normally to form a blastocyst
  Blastocyst is placed in the uterus of a surrogate ewe
• 5 months later a lamb is born - Dolly the sheep

Question 21

How does selective breeding work?

Answer 21

• A farmer decides which characteristic is most important
• Parents that show high levels of this characteristic are selected and bred
• Best offspring is chosen and bred again from this generation
• process repeated over generations until all animals have high levels of the desired characteristic

Question 22

How does genetic engineering work?

Answer 22

Genes from the chromosomes of humans and other organisms can be ‘cut out’ using enzymes and transferred to cells of other organisms

Question 23

How is insulin produced?

Answer 23

• Gene that codes for insulin is extracted from normal human cell using enzyme
• A plasmid is isolated from a bacterium and the human insulin gene is inserted
• plasmid vector is inserted into a bacterium
• Bacteria reproduces, producing new bacteria that all have the plasmid vector and produce insulin
• Insulin can be extracted and used to treat people with diabetes

Question 24

Advantages of genetic engineering

Answer 24

Quicker than selective breeding, can produce medicinal drugs, produces crops with specific characteristics

Question 25

Disadvantages of genetic engineering

Answer 25

Unknown long term effects, can bring up ethical issues, possible escape of genes into wild population, high cost to poorer farmers