Unit 4: Inheritance

Question 1

Define GENOTYPE:

Answer 1

the GENETIC CONSTITUTION 📜 of an organism - the alleles an organism has

Question 2

what’s meant by the “F2 generation” aka F squared

Answer 2

the SECOND set of offspring

Question 3

Define HOMOZYGOTE:

Answer 3

organism that carries TWO copies of the SAME allele e.g. bb

Question 4

Define HETEROZYGOTE:

Answer 4

organism carries two DIFFERENT alleles e.g. Bb

Question 5

What does it mean if a characteristic is said to be SEX LINKED?

Answer 5

the ALLELE that codes 📲for the characteristic is carried on a SEX CHROMOSOME 🍆

Question 6

Define GENE

Answer 6

a SEQUENCE 🌊 of BASES on a DNA MOL that codes 📲 for a PROTEIN (polypeptide) which results in a characteristic 👱

Question 7

two genetic disorders caused by sex linkage:

Answer 7

• Haemophilia 💔

* Colour Blindness 😎

Question 8

Blood Group Alleles:
Ia
Ib
Io

rank them in hierarchy of dominance

Answer 8

Ia and Ib co dominant

Io is recessive

Question 9

What does a Genetic Pedigree Diagram show?

Answer 9

An INHERITED TRAIT in a group of RELATED individuals

Question 10

How is Cystic Fibrosis caused?

Answer 10

Faulty RECESSIVE allele

Question 11

Define GENE POOL 🏊

Answer 11

the complete RANGE of ALLELES present in a POPULATION

Question 12

Define Allele Frequency

Answer 12

How OFTEN an ALLELE occurs in a POPULATION

Question 13

What does the Hardy-Weinberg principle predict?

Answer 13

the FREQUENCY of ALLELES in a POPULATION remains CONSTANT one generation to the next 👴 ➡️ 👶

Question 14

Criteria for the Hardy Weinberg principle to be true:

Answer 14

• NO mutation
• NO selection
• LARGE population
• Mating at RANDOM
• NO migration

Question 15

Equation to predict ALLELE FREQUENCY:

Answer 15

P + Q = 1

Question 16

Equation to predict GENOTYPE frequency?

Answer 16

p2 + 2pq + q2 = 1

Question 17

What is allele frequency affected by?

Answer 17

Dhanya (Differential)
Ruined (Reproductive)
Stephen (Success)

i.e. allele ⬆️ their chance of survival

Question 18

The two different types of Selection:

Answer 18

• DIRECTIONAL selection 🏃

* STABILISING selection 🚶

Question 19

When does STABILISING selection 🚶occur?

Answer 19

individuals with ALLELES for CHARACTERISTICS to the MIDDLE of the RANGE are more likely to
• survive and reproduce 👶

• occurs when environment 🌍 IS NOT changing
• reduces the range of possible PHENOTYPES

Question 20

When does DIRECTIONAL selection 🏃 occur?

Answer 20

individuals with ALLELES for CHARACTERISTICS of an ❌treme TYPE are more likely to
• survive and reproduce
• in response to an ENVIRONMENTAL CHANGE 🌏

Question 21

Explain how Speciation occurs (6 marks):

Answer 21

• Geographical isolation 🌍
• NO interbreeding between populations 👶
• Variation due to mutation
• DIFF. selection pressures
• DIFF. REPRODUCTIVE SUCCESS
• leads to change in ALLELE FREQUENCY
• Occurs over a LONG PERIOD OF TIME

Question 22

Define “Dominant” allele:

Answer 22

is ALWAYS e✖️pressed in the PHENOTYPE

Question 23

Define “Recessive” allele:

Answer 23

• Only expressed in the PHENOTYPE when TWO alleles are present
• is NOT expressed when HETERozygous