Chapter 30 - Monohybrid inheritance

Question 1

What is inheritance?

Answer 1

Receiving genetic material from parents

Question 2

Define genotype

Answer 2

Genetic make-up of an organism

Question 3

Phenotype

Answer 3

Physical appearance

Question 4

Homozygous

Answer 4

Same alleles for a characteristic

Question 5

Heterozygous

Answer 5

Different alleles for a characteristic

Question 6

Dominant

Answer 6

Allele visible in phenotype

Question 7

Recessive

Answer 7

Only shows in genotype is homozygous recessive

Question 8

State the 7 steps in creating a genetic diagra

Answer 8

1. Parental Phenotype
2. Parental Genotype
3. Gametes
4. Fertilisation
5. Offspring Genotype
6. Offspring Phenotype
7. Ratio

Question 9

State the 4 different genetic ratios

Answer 9

Aa x Aa 3:1
Aa x aa 1:1
AA x aa 4:0
Codominant cross 1:2:1

Question 10

Explain codominance

Answer 10

Both alleles have an effect on the phenotype. They are equally dominant or recessive

Question 11

Explain Albinism

Answer 11

• Little or no melanin in eyes, skin and hair
• Organism with NO melanin = albino
• Organism with LITTLE melanin = albinoid
• Albinism is a genetic mutation

Question 12

Describe sickle cell anaemia

Answer 12

• Red blood cells have crescent shape
• Abnormal haemoglobin called Haemoglobin S
• Sickle cells deliver less oxygen
• Red blood cells can break or get stuck
• This causes lots of pain
• It is a recessive allele
• Normal people suffer from malaria, suckle cell people do not

Question 13

Explain the different blood groups in terms of dominance

Answer 13

AB are codominant

O is recessive

Question 14

Explain sex linkage

Answer 14

• Gene that is only found on sex chromosomes is defined as a sex-linked gene
• Sex linked diseases are faulty genes on sex chromosomes
• X-chromosome is larger than Y-chromosome
• Therefore females will have two alleles for certain characteristics, where males have just one

Question 15

Describe haemophilia

Answer 15

• Impairs blood clotting
• More likely to occur in males
• Y chromosome has no allele to cancel out the fauly gene on the X-chromosome
• It is a recessive allele on the X-chromosome

Question 16

Describe colour blindness

Answer 16

• Sex linked

- Can not distinguish between red and green

Question 17

Explain how Downs Syndrome occurs

Answer 17

During gamete formation, the two X-chromosomes do not separate
The ovum has an extra X chromosome
The ovum now has 24 chromosomes instead of 23
The excessive X chromosome moves to chromosome pair 21, causing it to have three chromosomes
Downs syndrome is a chromosome mutation

Question 18

Define a mutation

Answer 18

A random, sudden change in genetic material OR number of chromosomes.