Chapter 18

Question 1

Gregor Mendel (1822-1884)

Answer 1

A pioneer of genetics, responsible for the laws governing inheritance of traits. Laws which he developed via studying the inheritance of traits in pea plants

Question 2

Monohybrid vs Dihybrid

Answer 2

Monohybrid cross is the cross involving a single trait. While Dihybrid cross is the cross involving two traits

Question 3

Alleles

Answer 3

The two forms of a gene (dominant & recessive)
Ex. R and r

Question 4

Genotype

Answer 4

Gene combination for a trait
(ex. RR, Rr, rr)

Question 5

Phenotype

Answer 5

The physical features resulting from a genotype
(ex. Red, white, yellow, etc)

Question 6

Homozygous genotype

Answer 6

Gene combination involving 2 dominant or 2 recessive genes (ex. RR or rr)
Also called “pure”

Question 7

Heterozygous genotype

Answer 7

Gene combination of one dominant & one recessive allele (ex. Rr); also called hybrid

Question 8

Reproduction in flowering plants

Answer 8

Pollen produced by the stamen contains the sperm while the ovaries are found inside the flower. The flowers can either self fertilize or cross fertilize

Question 9

Mendel’s Laws of Heredity

Answer 9

1. Inherited characteristics are controlled by genes that occur in pairs
2. Law of Dominance; One factor or gene masks effect of another
3. Law of Segregation; the two alleles in gametes separate from eachother during formation then reform at fertilization producing the genotype (During Anaphase 1)
4. Law of Independent Assortment; Alleles for different traits are distributed to sex cells (& offspring) independently of one another

Question 10

Pedigree Charts

Answer 10

A pedigree chart is like a family tree in which the inheritance of a trait can be traced from parents to offspring

Question 11

Pleiotropy

Answer 11

Pleiotropy is a genetic phenomenon where a single gene or DNA variant influences multiple traits, or phenotypic expressions. (One gene, many effects)

Ex. Dwarfism, gigantism, cystic fibrosis and sickle cell anemia

Question 12

Sickle-cell anemia

Answer 12

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Question 13

Marfan’s syndrome

Answer 13

An inability to produce normal connective tissue, is also associated with a single gene. Symptoms of Marfan’s Syndrome show up as eye skeleton and cardiovascular defects

Question 14

Co-dominance
or Intermediate Inheritance

Answer 14

Codominance essentially means that no allele can block or mask the expression of the other allele. Causing both genes to be expressed at the same time