Inheritance

Question 1

What is a genome?

Answer 1

The entire DNA of an organism

Question 2

What is a gene?

Answer 2

A short length of DNA that carries the genetic code that determines characteristics by instruction cells to produce a particular protein

Question 3

Describe the structure of DNA

Answer 3

A double helix with four bases
Adenine and thymine
Guanine and cytosine
Angry tiger called Greg

Question 4

What is RNA?

Answer 4

A single stranded molecule
Contains the base uracil instead of thymine

Question 5

What is a chromosome and where is it found?

Answer 5

A chromosome is a long length of DNA that has been coiled up. They are found in the nucleus of cells.

Question 6

What is an allele?

Answer 6

Different versions of the same genes, which give different characteristics, are called alleles

Question 7

What is a dominant allele?

Answer 7

A dominant allele is always expressed, even if one copy is present

Question 8

What is a recessive allele?

Answer 8

A recessive allele is only expressed if the individual has two copies and does not have the dominant allele of that gene

Question 9

What does heterozygous mean?

Answer 9

If there are two different alleles for a particular gene

Question 10

What does homozygous mean?

Answer 10

If there are two alleles the same for a particular gene

Question 11

What is a phenotype?

Answer 11

The characteristics that alleles produce

Question 12

What is a genotype?

Answer 12

the collection of alleles that determine an organism’s characteristics

Question 13

What is codominance?

Answer 13

When neither alleles are recessive, so characteristics from both alleles are shown

Question 14

What is polygenic inheritance?

Answer 14

Characteristics that are controlled by more than one gene are described as being polygenic. Most characteristics are a result of multiple genes interacting, rather than a single gene. An example of polygenic inheritance is eye colour – while it is true that brown eyes are dominant to blue eyes, it is not as simple as this as eye colour is controlled by several genes

Question 15

How is the sex of a person controlled?

Answer 15

Of the 23 pairs of chromosomes, one determines sex. Males must have both an X and Y chromosomes and females have 2 X chromosomes.

Question 16

What are the chances of having a girl or boy?

Answer 16

When you use a genetic diagram to show sex, you would get a 50/50 chance of either sex. This is because sex depends on whether the sperm carries an X or Y chromosome.

Question 17

What does diploid mean?

Answer 17

The nucleus contains two copies of each chromosome. The diploid number for humans is 46

Question 18

What does haploid mean?

Answer 18

A nucleus that has a single set of unpaired chromosomes

Question 19

What is variation caused by?

Answer 19

Genes cause variation, e.g. eye colour, hair colour
Environment also causes variation
Some variation is caused by both e.g. health (genetic risk and lifestyle), intelligence and sporting ability

Question 20

What is a mutation?

Answer 20

A rare, random change in an organism’s DNA that can be inherited

Question 21

What is Darwin’s theory of evolution?

Answer 21

Life began as simple organisms and more complex organisms evolved. Organisms with more suitable characteristics for their environment have a better chance of survival and so will pass their genes on. Over time, this characteristic will become more common so the species is better able to survive and the species has adapted to its environment.

Question 22

How can bacteria become resistant to antibiotics?

Answer 22

1. Bacteria mutates and sometimes a mutation can mean the bacteria is less affected by an antibiotic
2. The bacteria is better able to survive in the host so live for longer and reproduces much more often
3. The allele for resistance is passed on and becomes more popular over time and the bacteria can’t be treated by that antibiotic anymore
4. Sometimes drug companies invent new antibiotics but ‘superbugs’ that are resistant to most known antibiotics are becoming more common