SB3g-i

Question 1

What do chromosomes contain?

Answer 1

Genes.

Question 2

What is a gene?

Answer 2

A piece/section of DNA.

Question 3

What is the purpose of a gene?

Answer 3

Contain instructions for a certain characteristic.

Question 4

What are alleles?

Answer 4

Different forms of the same gene.

Question 5

What is the least amount of alleles for every gene?

Answer 5

2.

Question 6

What is monohybrid inheritance?

Answer 6

The inheritance of one gene at a time.

Question 7

What is a dominant allele?

Answer 7

An allele that overrides an equivalent recessive allele and always shows its characteristic.

Question 8

How do we represent a dominant allele?

Answer 8

With a capital letter e.g. “B”

Question 9

What is a recessive allele?

Answer 9

An allele that is overridden by an equivalent dominant allele and remains hidden. It can only be expressed and show the characteristic when it is found with another recessive allele.

Question 10

How do we represent a recessive allele?

Answer 10

Show with a lowercase letter e.g. “b”

Question 11

What alleles are present when there is a heterozygous characteristic?

Answer 11

Two different alleles for one particular gene.

Question 12

What alleles are present when there is a homozygous characteristic?

Answer 12

Two identical alleles for one particular gene.

Question 13

What is a genotype?

Answer 13

The combination of alleles.

E.g. homozygous dominant / BB

Question 14

What is a phenotype?

Answer 14

The appearance of the organism.

E.g. brown eyes

Question 15

What are the two types of sex chromosomes?

Answer 15

• X chromosome
• Y chromosome

Question 16

What chromosomes do egg cells carry?

Answer 16

X chromosomes.

Question 17

What chromosomes do sperm cells carry?

Answer 17

Either X or Y chromosomes.

Question 18

How do we demonstrate inheritance?

Answer 18

• Punnet Squares
• Genetic diagrams

Question 19

How do we show how genotypes and their resulting phenotypes are inherited in families?

Answer 19

Using a genetic pedigree diagram.

Question 20

What is codominance?

Answer 20

When both alleles for the characteristic are dominant and they are both expressed.

Question 21

What blood groups are there?

Answer 21

• A
• B
• AB
• O

Question 22

What are the three alleles that control the blood group and how are they represented?

Answer 22

A, B and O.

A = Iᴬ
B = Iᴮ
O = Iᴼ

Question 23

Which are the dominant and recessive blood group alleles?

Answer 23

Dominant: Iᴬ, Iᴮ
Recessive: Iᴼ

Question 24

When do sex-linked disorders occur?

Answer 24

When the faulty allele is located on the X chromosome.

Question 25

What happens to a female with a faulty recessive allele on a sex chromosome?

Answer 25

The female could either be a carrier, healthy or diseased.

Question 26

What happens to a male with a faulty recessive allele on a sex chromosome?

Answer 26

The male will either be healthy or diseased.

Question 27

Why can a male never be a carrier of a recessive sex-linked disease?

Answer 27

They only have one X chromosome.

Question 28

How does colour blindness occur?

Answer 28

Due to a recessive allele on the X chromosome.

Question 29

Why does colour blindness have its effects?

Answer 29

Colour vision is due to cones found in the eye and the ability to see light is the result of multiple genes. Mutation in these genes affect the ability to see and distinguish different colours.

Question 30

Which gender is colour blindness more common in and why?

Answer 30

Men since colour blindness is caused by a recessive allele and they only have one X chromosome.

Question 31

What are the different examples of colour blindness in males and females?

Answer 31

Females: - Homozygous dominant (XᴮXᴮ) normal vision - Homozygous recessive (XᵇXᵇ) colour blind - Heterozygous (XᴮXᵇ) normal vision Males: - XᴮY normal vision - XᵇY colour blind

Question 32

How does haemophilia occur?

Answer 32

Due to a recessive allele on the X chromosome.

Question 33

What is haemophilia?

Answer 33

When blood does not clot normally so bleeding is very difficult to stop.

Question 34

What are the different examples of haemophilia in males and females?

Answer 34

Females: - Homozygous dominant (XᴴXᴴ) healthy - Homozygous recessive (XʰXʰ) zygote does not survive - Heterozygous (XᴴXʰ) healthy and carrier Males: - XᴴY healthy - XʰY haemophiliac