LEC 17

Question 1

Law of Independent Assortment

Answer 1

The alleles of different genes are distributed to the egg and sperm cells independently of each other during meiosis.

Question 2

Mendel’s Second Law

Answer 2

Law of Independent Assortment (ONLY PARTIALLY CORRECT)

Question 3

Incomplete Dominance

Answer 3

Heterozygous genotype results in a phenotype that is in between the two homozygous conditions

Question 4

Incomplete Dominance Example

Answer 4

In Caucasians, curly hair (cc) combined with straight hair (ss) results in an offspring with wavy hair (sc)

Question 5

Co-dominance

Answer 5

1. A pair of non-identical alleles specify two different phenotypes
2. If both non-identical alleles are inherited, both phenotypes are expressed equally

Question 6

Co-dominance Example:

Answer 6

Blood types
- Have three (3) possible alleles: A, B and O
- O is recessive, A & B are co-dominant

Question 7

Polygenetic Inheritance
Examples

Answer 7

Phenotype is influenced by multiple genes working together

Question 8

Polygenetic Inheritance Examples

Answer 8

Eye color is controlled by at least 3 genes and can result in a range of different eye color phenotypes (nearly black to light blue)

Height, body size and shape are polygenic

Question 9

Polygenetic Inheritance Characteristics

Answer 9

Tend to have a continuous range of variation in the population (more people in the middle and fewer people at the extremes) (BELL CURVE)

Question 10

Heritable diseases

Answer 10

Our genes make us more susceptible to increased risk for conditions such as skin cancer, high cholesterol and heart diseasex

Question 11

Environmental Influences

Answer 11

Interdependence between genes & the environment

Question 12

Epigenetics (2)

Answer 12

Study of how traits can be changed or passed down without changing the DNA sequence itself.

Looks at how genes are turned “on” or “off” by factors like environment, lifestyle, or age.

Question 13

Epigenetics Examples

Answer 13

1. Environmental factors can modify the DNA without changing the nucleotide sequence
2. Adding a methyl (-CH3) group to DNA regions or changing the way DNA is wound around histones

Question 14

Linked Alleles DEF

Answer 14

Many alleles for different traits are often inherited together because they are physically “linked” or joined on the same chromosome

However, they are NOT always inherited together - may get shuffled during crossing-over in meiosis I

Question 15

The likelihood of inheriting the two alleles together is dependent on: (2)

Answer 15

1. How close together the two alleles are on the chromosome (the closer they are, the higher the chance of them staying together)
2. How often crossing-over occurs (the more cross-over the lower the chance of the alleles staying together)

Question 16

Genetic Pedigrees can be used to:

Answer 16

1. Shows typical inheritance patterns in a chart form
2. Uses standard methods, definitions and symbols
3. Relies on knowledge of probability and Mendelian genetics

Question 17

Punnett squares help to determine ______________ expression

Answer 17

1. phenotype