Genetics: Mendel, Genetic Crosses, Traits

• Test date is Thursday, February 27, 2025

Gregor Mendel

• Gregor Mendel is known as "The Father of Modern Genetics"
• He determined dominant and recessive traits using pea plants
• His detailed notes made it easier for scientists to understand

Genetic Crosses with Pea Plants

• Dominant trait is yellow
• Recessive trait is green
• The genotype of the pure-breeding yellow line is YY
• The genotype of the pure-breeding green line is yy

Inherited vs Aquired Traits

• Inherited traits are passed down from family members
• Acquired traits result from doing something

Homologous Chromosomes

• There are 5 genes on this chromosome example
• Genes that are heterozygous are s, S, and Rr
• Genes that are homozygous are QQ, tt, UU
• A human body cell contains 46 chromosomes

Punnett Squares and Pedigrees

• A heterozygous man for tongue rolling (dominant) marries a woman non-tongue roller (recessive)
• The probability the child will be a tongue roller is 2/4
• The probability the child will not roll his or her tongue is 2/4
• The probability that the child would be homozygous dominant is 0
• Cross of two heterozygous curly-haired dogs
• Possible genotypes of possible puppies are CC Cc, Cc cc
• Possible phenotypes of possible puppies are curly hair or straight hair
• The probability that a puppy would be heterozygous is 2/4
• The probability that a puppy would have curly hair is 3/4

Pedigree

• A pedigree traces an inherited disease through a family
• Four generations are shown from the original parents (A and B) to offspring D
• The disease is recessive because the parents are unaffected, but the children are affected, with only some shaded, and most aren't shaded
• Persons A and B are not directly affected
• Persons A and C are father and daughter
• The genotype of Person A is Bb
• The genotype of Person B is Bb
• The genotype of Person C is bb

DNA Structure and Function

• The genetic code is like a "blueprint" of the cell
• It's like a chore sheet or to-do list
• DNA has a double helix shape
• The 4 bases that make up the rungs of the DNA ladder are thymine, cytosine, adenine, and guanine
• Adenine bonds with thymine, and guanine bonds with cytosine
• Complementary strand:
  • ATC CGT GTC AAT GGC CCG
  • TAG GCA CAG TTA CCG GGC
• The sides of a DNA molecule are called the backbone and are made of sugar and phosphate
• DNA is found in the nucleus of an animal cell

Mutations

• Original DNA: AAA TGG TAC TGT
  • Mutation A (AAA TGG ACT GT): deletion
  • Mutation B (AAA TGA GTA CTG T): addition
  • Mutation C (AAA TCG TAC TGT): substitution
• Mutations can be harmful, beneficial, or neutral to an individual
  • Harmful mutations can cause diseases like Tay-Sachs or sickle cell anemia
  • Beneficial mutations provide more protein and do their job
  • Neutral mutations might have diseases that are not so severe that the other cell can heal the body
• They create variation among populations
• Variation is beneficial because it helps people learn more things and not everybody is the same

Genes and Heredity

• Eye color is inherited, meaning it is derived from either or both parents
• A gene is a specific segment in DNA that produces protein
• Chromosomes are like a case for a gene, storing all the genes
• If DNA is inside a cell's nucleus and instructions for a specific protein need to travel outside the Ribosomes, mRNA is used
• An allele is a variant of a particular nucleotide sequence with at least 2 for every trait
• Alleles are different from each other, matching with each other, and inherited from each parent
• Dominant alleles are represented with a capital letter
• Recessive alleles are represented with a lowercase letter
• Genotype is the sequence of the allele and Phenotype is how it looks
• A dominant homozygous allele is CC
• A recessive homozygous allele is cc
• A heterozygous allele is Cc, also known as a hybrid

Explore Gregor Mendel's contributions to genetics, including his work with pea plants and the discovery of dominant and recessive traits. Learn about genetic crosses, inherited versus acquired traits, homologous chromosomes, and how to use Punnett squares and pedigrees to determine genetic probabilities.