Genetics

Question 1

Why did Mendel use pea plants to study genetics?

Answer 1

Pea plants are a model system because they have easy characteristics to study
- The understanding of these plants can be applied to other systems

Pea plants can be considered a true-breeding plant
- True breeding : the plant produces an offspring that look like its parents

Pea pants grow quickly
- It can be easily harvested and lots of seeds (data) can be obtained over several pea generations

Question 2

Continuous vs Discontinuous Variation

Answer 2

• Continuous = range of small differences within a trait
• Ex : height
• Discontinuous = discrete, distinguishable traits
• Ex : blood type

Question 3

Dominant vs Recessive Traits

Answer 3

Dominant traits continue to be expressed in a hybrid
- The trait will present itself more often

Recessive traits become latent in a hybrid but can reappear in later generations

Question 4

Inheritance of Genes

Answer 4

Each individual has two copies of characteristic
(genes)

During gamete formation (meiosis), only one copy is carried in gamete (sex) cell
- Results in a haploid set of chromosomes

After fertilization, the zygote has a diploid (2) set of chromosomes and the genes therein
- New individual now has two copies of genes

Question 5

Genotype vs Phenotype

Answer 5

Genotype : is the genetic make-up of an individual

Phenotype : is the outward expression of those genes

Question 6

Homozygous Dominant & Expression

Answer 6

BB
- Two copies of dominant traits

Expression : Dominant trait will be presented

Question 7

Heterozygous & Expression

Answer 7

Bb
- One copy of dominant trait and one copy of recessive trait

Expression : Dominant trait will be presented

Question 8

Homozygous Recessive & Expression

Answer 8

bb
- Two copies of recessive traits

Expression : Recessive trait will be presented

Question 9

Dominance

Answer 9

Heterozygous organisms will express the dominant trait and appear similar to homozygous-dominant individuals
- Recessive allele can still be transmitted to next generation

Question 10

Punnett Squares

Answer 10

A way to calculate probabilities for offspring
- Shows possible combinations of alleles

Parents are along the X and Y axes
- Copy of gene goes into separate column or row

Offspring have genotype where columns
and rows intersect
- Phenotype depends on alleles present