Mendelian Genetics

Question 1

Which sexually producing organisms are unique?

Answer 1

Diploid apart from monozygotic multiplies

Question 2

In his studies of peas, how many traits were studied?

Answer 2

7

Question 3

What were these traits?

Answer 3

round or wrinkled
yellow or green interior
purple or white petals
inflated or pinched pods
green or yellow pods
axial or terminal flowers
long or short stems

Question 4

What is a phenotype?

Answer 4

trait, appearance (defined by genes)

Question 5

What is meant by dominant?

Answer 5

trait that persists in F1 generation of monohybrid cross

Question 6

What is meant by recessive?

Answer 6

trait that disappears in F1 generation but reappears in F1 cross

Question 7

What is Mendel’s 1st law?

Answer 7

Each trait is governed by two hereditary determinants (alleles of a gene)

If a parent has two different alleles, each will be passed on in equal proportions

Question 8

What is a allele?

Answer 8

variant copies of same gene

Question 9

What is meant by Genotype?

Answer 9

combination of alleles present

Question 10

What does the SBE1 gene encode?

Answer 10

a starch de-branching enzyme that converts starch to sucrose allowing pea hydration.

Question 11

Would starch conversion occur in a round pea?

Answer 11

Homozygous for 2 functional alleles
Heterozygous with 1 functional & 1 non functional
Starch sucrose conversion takes place and pea is hydrated

Question 12

Would starch conversion occur in a wrinkled pea?

Answer 12

Homozygous for 2 non functional SBE1 alleles

Conversion does not take place, pea remains dehydrated (wrinkled)

Question 13

What does independent assortment of two genes predicts..?

Answer 13

a 9:3:3:1 phenotype ratio

Question 14

What is Mendel’s 2nd Law?

Answer 14

Where several traits are followed in a dihybrid cross, the traits segregate independently of each other.
(independent assortment)

Question 15

Where dihybrid crosses do not give the expected genotype and phenotype ratios, there is evidence of?

Answer 15

Genetic linkage

Question 16

Genes that are very close together on a chromosome tend to be inherited as ?

Answer 16

a single unit or haplotype.

Question 17

Genes which are physically linked on the same chromosome can still show ?

Answer 17

independent segregation.

Question 18

Which traits do not follow Mendelian inheritance pattern?

Answer 18

Real Non-Mendelian Inheritance

• Maternal inheritance
• Phenocopies

Question 19

Apparent Non-Mendelian Inheritance doesn’t follow Mendel’s inheritance pattern, what does it consist of?

Answer 19

Incomplete penetrance of dominant traits, where the individual has the dominant allele but does not express the phenotype – important in medical genetics
Incomplete dominance – trait is intermediate
Lethal alleles (homozygosity for lethal allele removes a genotype option in the offspring)
Traits governed by linked genes (linkage phase)
Traits were a gene governs several traits

Question 20

Why do all children of affected mother express trait, but no children of affected father do?

Answer 20

traits are determined by genes on mitochondrial genome and all mitochondria in egg cells are maternal in origin

Question 21

What is a phenocopy?

Answer 21

A phenocopy is a trait that is not the true phenotype determined by the genotype