Biology - Gr.11 🧬 (UNIT 1: GENETICS): Heredity & Inheritance

Who is the father of genetics? What was his experiment?

• Gregor Mendel

• Investigated the heredity of pea plants. Inheritance of a single characteristic (ex. flower colour)

Mendel’s 1st Law:

“PRINCIPLE OF DOMINANCE”

→ There are DOMINANT and RECESSIVE traits where certain alleles dominate over others

Mendel’s 2nd Law:

“PRINCIPLE OF SEGREGATION”

→ organisms inherit genes, one from each parent.

→ organisms donate only one copy of each gene to their gametes because the genes separate during gamete formation (Meiosis).

Mendel’s 3rd Law:

 “LAW OF  INDEPENDENT ASSORTMENT”

→ dihybrid crosses

→ If genes are located on separate chromosomes, they will be inherited independently of one another.

What are the types of genetic crosses

• Monohybrid crosses

• Dihybrid crosses

• Incomplete dominance

• Lethal Alleles

• Complete dominance

• Blood type crosses

• Polygenic Inheritance*

A parent could be…

• unaffected: if he does not have the gene and is not likely to pass it to his descendants

• carrier: if they are not affected by the disease, but if they have the gene transmitted to them by one of their own parents

• affected: if the illness manifests itself

What are THREE cases with the mother?

1. The mother is a carrier, but is not affected

   → If father carries, he is affected

   → If the father is healthy, only half the kids will carry it.

2. The mother is affected

   → Father is affected, all children will be affected

   →If father is not affected, all boys will be affected and girls would have the risk of passing it on

3. The mother is healthy and the father is affected

   → All girls are carriers, the boys will be healthy

What are the FOUR chromosmal mutations?

• Deletion

• Duplication

• Addition

• Translocation

What is silent mutation?

code changes, but the amino acid/protein does not. ex CUU → CUC

What causes mutations?

• environmental factors (induced)

• random errors in DNA replication, repair, recombination (crossing over)

What is point mutation?

small scale change in sequence of nitrogenous bases

→ FRAME-SHIFT (insertion or deletion): one or more nucleotides add/deleted

Types of cells where mutation occurs:

• SOMATIC - not passed down

• GERM CELL - passed down

Sickle-cell (ANEMIA)

AA - normal

Aa - Carrier

aa - affected

*protection against malaria

practice (header)

—

Monohybrid Cross (use punnet squares):

1. A brown eyed man and a brown eyed woman decide to have children. If both are heterozygous, what possible genotypes and phenotypes might their offspring have? (Brown is dominant)

Possible Genotypes:

• BB – Homozygous dominant

• Bb – Heterozygous

• bb – Homozygous recessive

Genotype Ratios:

• 1 BB : 2 Bb : 1 bb

Phenotypes:

• Brown eyes (BB or Bb) – Dominant

• Blue eyes (bb) – Recessive

Phenotype Ratios:

• 3 Brown : 1 Blue

— (percents)

Their children have:

• A 75% chance of having brown eyes

• A 25% chance of having blue eyes
  And genetically:

• 25% will be BB

• 50% will be Bb

• 25% will be bb

2. Suppose that a cross had been performed with a garden pea, between parents with round seed (RR) and a parent with wrinkled seeds (rr). What would be the genotypes and phenotypes in the F1 generation? If two F1 offspring were crossed to produce F2 generation, what would be the resulting genotypes and phenotypes?

F1

Genotype(s): All Rr

Genotype Ratio: 100% Rr

Phenotype(s): All round

Phenotype Ratio: 100%

F2

Genotype(s): RR, Rr, rr

Genotype Ratio: 1:2:1

Phenotype(s): Round, wrinkled

Phenotype Ratio: 3 round: 1 wrinkled

3. A black rabbit is crossed with a white rabbit and one of the seven offspring is white. What is the genotype of the black rabbit parent?

The genotype of the black rabbit is Bb.

Dihybrid Crosses (use punnet squares):

1. Two pea plants are crossed, one parent plant is dwarf, yellow-padded (ttgg) and the other parent is homozygous tall and homozygous green-padded (TTGG). Find:

   a) the F1 gen phenotypes and genotypes

   b) the F2 gen phenotypes and genotypes

a) F1:

Genotype: 100% TtGg
Phenotype: 100% Tall with green-padded

b) F2

Genotypes:

TTGG, TTGg, TtGG, TtGg → Tall, green

TTgg, Ttgg → Tall, yellow

ttGG, ttGg → Dwarf, green

ttgg → Dwarf, yellow

Phenotypes:

9:3:3:1

2. Brown hair colour in hamsters are dominant to white. Long hair is dominant to short. If a homozygous white long haired male is crossed with a heterozygous brown, short haired female, what are the genotypes and phenotypes for the F1 generation?

F1 Genotypes:

BbLl (brown, long)

bbLl (white, long)

F1 Phenotypes:

50% brown, long hair

50% white, long hair

—

100% long hair

50% brown and 50% white