Genetics 1

Question 1

What are mendel’s two laws?

Answer 1

1) Law of segregation: A parent gives one allele for a gene (consists of a pair of alleles) to each gamete (egg or sperm) they produce.
- occurs in anaphase 1 (separating)
2) law of independent assortment: During gamete formation different pairs of alleles in a gene segregate independently of each other.
- In other words the inheritance of one allele a gamete receives has no affect on the inheritance of the other.

• occurs in metaphase 1 (lining up)
• occurs in anaphase 1 (separating)

Question 2

What is genotype and phenotype?

Answer 2

• Genotype: Genetic makeup of an organism

- Phenotype: Observable traits in an organism

Question 3

1) what is homozygous alleles?
2) what is heterozygous allele?

(Genotypes)

Answer 3

1) homozygous alleles: the same alleles
Ex:
- homozygous recessive: aa
- homozygous dominant: AA

2) heterozygous alleles: Different alleles; one dominant and one recessive
Ex:
-Aa

Question 4

What are other forms of inheritance that are non-Mendelian?

Answer 4

DESCRIPTION: A homozygous dominant allele (AA) expresses a red flower, a homozygous recessive allele (aa) expresses a white flower

• Codominance: both alleles are expressed in a heterozygous individual.

Ex: if a flower has the gene Aa, the flower will show patches of red and white.

• Incomplete dominance: a dominant allele does not completely mask the recessive allele, so colours blend.

Ex: If the flower has an allele that is Aa the flower I’ll be pink.

Question 5

What is polygenic inheritance?

Answer 5

It’s when more than one gene determines a character.

Ex: skin colour, eye colour, hair

Question 6

What is pleiotropy?

Answer 6

It’s when a single gene has Multiple phenotypic effects.

Ex: one mouse has fur and another does not.

Question 7

Give an example on how the environment can influence gene action?

Answer 7

Skin tones could also be enhanced by usage of suntan lotions

Question 8

What is monohybrid cross?

Answer 8

• it is used to study the dominance of genes
• the law of segregation is explained by this cross
• the phenotypic ratio is 3:1
• the genotypic ratio is 1:2:1

Question 9

What is a dihybrid cross?

Answer 9

• it is used to study offspring assortment
• the law of independent assortment is explained by this cross
• the phenotypic ration is 9:3:3:1
• the genotypic ratio is 1:2:2:4:1:2:1:2:1 (not important)