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Mendel and Heredity. Mendel and Heredity Terms. Gregor Mendel- “Father of Genetics” Traits - characteristics that are inherited Ex. Eye color, hair color Genetics- study of biological inheritance patterns Purebred- offspring inherit all of parents characteristics,

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mendel and heredity terms
Mendel and Heredity Terms
  • Gregor Mendel- “Father of Genetics”
  • Traits- characteristics that are


    • Ex. Eye color, hair color
  • Genetics- study of biological inheritance patterns
  • Purebred- offspring inherit all

of parents characteristics,

genetically uniform

mendel and heredity terms1
Mendel and Heredity Terms
  • Cross- mating of two organisms
  • Gene- piece of DNA that provides a set of instruction to a cell
  • Allele- any alternative form

of a gene that may occur

mendel and heredity terms2
Mendel and Heredity Terms
  • Homozygous- two of the same alleles
  • Heterozygous- two different alleles
mendel and heredity terms3
Mendel and Heredity Terms
  • Genotype- genetic makeup of a specific set of genes
  • Phenotype- physical characteristics or appearance of an organism
  • Dominant- allele is expressed when two different alleles are present
  • Recessive- allele is expressed only when two copies are present
  • In the 1800’s, Gregor Mendel laid the groundwork for modern genetics
  • He crossed many pea plants and observed traits of offspring
  • Discovered that
    • Organisms inherit two copies of each gene, one from each parent
  • Peas either:
    • Round (dominant)
    • Wrinkled (recessive)
  • GenotypesPhenotypes
    • RR (homozygous dominant) -round
    • Rr (heterozygous) -round
    • rr (homozygous recessive) -wrinkled
  • Another example:
  • Brown (dominant) vs. black (recessive)
  • Genotypes? Phenotypes?
  • Mendel’s discoveries led to the Punnett square
  • Developed by R.C. Punnett
  • Used to predict genotypes of offspring
  • Example:
    • Straight (dom.) vs. curly (rec.)
    • Dad-heterozygous
    • Mom-homozygous recessive
dihybrid punnett square
Dihybrid Punnett Square
  • Predicting more than one trait
  • EX. Cross a tall pea plant with green leaves with a short pea plant with yellow leaves.
    • Determine parent genotypes.
    • Find combinations of alleles.
    • Fill out Punnett square.
    • Determine phenotypes of offspring.
dihybrid punnett square1
Dihybrid Punnett Square
  • EX. Cross a tall (homozygous) pea plant with green (heterozygous) leaves with a short pea plant with yellow leaves. (Tall is dominant to short, green is dominant to yellow)
dihybrid practice
Dihybrid Practice
  • Cross the parents SsYy x SsYy









Smooth/Yellow __9____

Smooth/Green ___3___

Rough/Yellow ____3__

Rough/Green _____1_

bellringer complete both questions in your notebook
Bellringer:Complete both questions in your notebook
  • 1. In one particular species of cats, long hair is dominant to short hair. If a heterozygous male is crossed with a homozygous recessive female, what is the probability that one of the offspring has long hair?
  • 2. A homozygous dominant flower is crossed with a homozygous recessive flower. Purple flowers are dominant to red flowers. What are the genotypes and phenotypes of the offspring?
sex linked genes
Sex-linked Genes
  • Sex-linked genes- genes located on the sex chromosomes
    • Female (XX), Male (XY)





incomplete dominance
Incomplete Dominance
  • Alleles that show incomplete dominance show both the dominant and recessive traits
  • Neither allele is completely dominant or recessive
  • Ex. If a homozygous red

flower and homozygous white

flower cross, the offspring

have pink flowers

  • Both the dominant and recessive alleles are expressed
  • Ex. Red and white flower are crossed, the offspring will be red and white
exit slip
Exit Slip
  • Sex linked genes are located ______________.

2. A dog that shows the phenotypes of both his mother and father would be an example of (incomplete or codominance).

3. A blue flower crosses with a yellow flower to produce a green flower. This is an example of (incomplete or codominance).

  • Pedigree- chart that can help trace phenotypes and genotypes in a family
    • Helps to determine if people carry the recessive allele
  • Reading a pedigree

○ □

□ ○ □

How many boy children?

How many girl children?

Is the oldest child a boy or girl?

dna structure
DNA Structure
  • DNA is a polymer made of monomers called nucleotides
  • Each nucleotide is made of:
    • A phosphate group
    • Deoxyribose (sugar)
    • Nitrogen containing base
types of nucleotides
Types of Nucleotides
  • C – Cytosine


  • T – Thymine
  • A – Adenine


  • G – Guanine
base pairing rules
Base-Pairing Rules
  • Nucleotides always pair in the same way
    • Thymine (T) always pairs with Adenine (A)
    • Cytosine (C) always pairs with Guanine (G)
    • Ex. TTACGTAG


dna structure1
DNA Structure
  • DNA is in the shape of a double helix
  • Each nucleotide is paired
exit slip1
Exit Slip
  • Thymine is an example of a _____________.
      • nucleotide

2. The shape of DNA is known as a ___________.

      • Double helix

3. Write the DNA base pair:



dna replication
DNA Replication
  • Replication is a process by which DNA is copied
  • Occurs during the S stage of the cell cycle