Inheritance, Variation & Evolution

Question 1

What type of plants did Mendel use?

Answer 1

Pea plants

Question 2

What 3 conclusions did Mendel reach?

Question 3

What were Mendel’s “units”?

Answer 3

Genes

Question 4

Cystic fibrosis.

Answer 4

A medical condition, where a thick, sticky mucus is produced. This coats the airways & lungs.
If the mucus is not cleared daily, there can be chest infections.

Question 5

Is cystic fibrosis caused by a recessive allele or a dominate allele?

Answer 5

A recessive allele.

Mnemonic (O)CR

Question 6

Polydactyly.

Answer 6

A medical condition that causes extra digits (fingers/toes) on the hands/feet.

Question 7

Is polydactyly caused by a recessive allele or a dominate allele?

Answer 7

A dominant allele.

Mnemonic PD

Question 8

Sickle cell anaemia.

Answer 8

A medical condition which causes mutations in red blood cells so they are less efficient at transporting oxygen around the body.

Question 9

Is sickle cell anaemia caused by a recessive allele or a dominate allele?

Answer 9

A recessive allele.

Mnemonic S(I)R

Question 10

What is unusual about sickle cell anaemia carriers?

Answer 10

The carriers are malaria-resistant.

Question 11

Huntington’s disease.

Answer 11

A medical condition where nerve cells in the brain are damaged, reducing the brain function.

Question 12

Is Huntington’s disease caused by a recessive allele or a dominate allele?

Answer 12

A dominant allele.

Mnemonic HD

Question 13

What type of substance does a gene code for?

Answer 13

Protein.

Question 14

Without medical treatment, people with sickle cell anaemia are frequently ill and have a reduced life expectancy.
The malarial parasite cannot live in the red blood cells of a person who has the H^S allele.
A scientist stated:
‘It is an advantage for people to have the H^S allele in countries where malaria occurs.’
Evaluate the scientist’s statement. [3 marks]

Note:
H^A is the normal haemoglobin allelle, producing normal red blood cells.
H^S is the mutated allele.

A person has sickle cell anaemia if they are homozygous for H^S.
A person who is heterozygous has sickle cell trait - both normal and abnormal haemoglobin in the red blood cells.

Got 1/3 marks in the Easter holiday.

Answer 14

any three from:

points for:
* H^AH^S do not get malaria
* H^AH^S survive sickle cell
anaemia

points against:
* H^AH^A may die from malaria
* H^SH^S may become (severely) ill with sickle cell anaemia

Judgement:
if parents HAH^S then some offspring survive both malaria and sickle cell anaemia
or
if parents HAH^S then some offspring may become (severely) ill with malaria and some become (severely) ill with sickle cell anaemia

to gain full marks both point(s) for and point(s) against must be given

Question 15

Figure 17 shows the relationship between the beak depth of parent birds and the beak depth of their offspring.

https://cdn.discordapp.com/attachments/1072263133764268164/1225848596704788673/image.png?ex=66229f78&is=66102a78&hm=d525710b1caff1aa554a8b7add07387be1bc3d8d4b261f936021223d1030631c&

Give evidence from Figure 17 that beak depth is an inherited characteristic. [1 mark]

Got 0/1 marks in the Easter holiday.

Answer 15

Offspring have similar beak depths to parents

ignore same beak depths
ignore positive correlation / described

Question 16

https://cdn.discordapp.com/attachments/1072263133764268164/1225849908406517771/image.png?ex=6622a0b1&is=66102bb1&hm=36f00f821bb14318ea9d560f1257cec093353878b006e85762fb920d83dda436&

The medium ground finch and the small ground finch both feed on seeds.
The size of seeds eaten by each bird depends on the depth of the bird’s beak.
The range of beak depth of medium ground finches on Isabela Island is different from the range on Daphne Island.
Explain what might have caused this difference. [6 marks]

Got 4/6 marks in the Easter holiday.

Answer 16

colonisers of Isabela have a range of beak depths
allow colonisers of Daphne have a range of beak depths

due to different combinations of alleles of several genes
or
due to different alleles of one gene
or
due to mutation

large range of (sizes / species of) seeds / food (on Isabela)
or
large(r) seeds (on Isabela)
allow small range of (sizes / species of) seeds / food on Daphne
or
allow small(er) seeds on Daphne

more competition for seeds / food (on Isabela)
allow less competition for seeds / food on Daphne
ignore competition unqualified

birds with larger beaks get enough food to (survive and) reproduce (on Isabela)
allow birds with smaller / medium beak sizes get enough food to (survive and) reproduce on Daphne

(survivors) pass on (beneficial) alleles to offspring
allow pass on genes / mutation
ignore pass on chromosomes / characteristics