Introduction%20to%20Mendelian%20Genetics

1
Introduction to Mendelian Genetics
2
Objectives

• Define key terms used in Mendelian Genetics

3
Key Terms

• Heredity The passing of characters from parents
  to offspring.
• Genetics The branch of biology that focuses on
  heredity.
• Traits Specific characteristics that vary from
  one individual to another. Ex. Hair color, skin
  color
• Gene- a specific nucleotide sequence of DNA that
  codes for a protein

4
Key Terms

• Allele alternative forms of a gene. Ex. flower
  color purple (P) or white (p)

5
Key Terms

• Phenotype- organisms expressed traits Ex. Brown
  coat
• Genotype An organisms genetic makeup the
  combination of alleles in the homologous
  chromosomes. Ex. - BB, Bb, bb
• Homozygous having identical alleles for the
  trait Ex. WW, ww
• Heterozygous having two different alleles for
  the trait- Ex.Ww.

6
Definitions

• Dominant- an allele that determines the phenotype
  of heterozygote. (Ex. YY-yellow plant or Yy).
• Recessive the allele that is masked by the
  dominant allele in heterozygotes
• not observed in the phenotype unless homozygous
  recessive (yy-green plant).

7
Purpose of Punnet Square

• Examines the probability of getting a particular
  phenotype based on combination of gametes
• Trait resides on the homologous chromosomes
• Each square in a monohybrid cross (i.e. one
  trait) represents 25 chance
• Summarize result with genotypic ratio and
  phenotypic ratio

8
Practice Problem

• Draw a Punnett square for the following cross
• Tt X Tt
• Give the genotypic and phenotypic ratio.

9
Practice Punnett Square Problem

• A plant that is heterozygous for green (G) pods
  is crossed with a plant that has yellow (g) pods.
  Green pod is dominant and yellow pod is
  recessive. What are the probable genotypic and
  phenotypic ratios in the offspring from this
  cross? What is the probability that plant will
  produce yellow pods?

10
Paraphrase
Write down two genetic terms you learned today
Write the definitions of those terms in your own
words
PROPERTY OF PIMA COUNTY JTED, 2010
11
Human Traits
12
Detached Earlobes
13
Hitchhikers Thumb
14
Tongue Rolling
15
Dimples
16
Cleft Chin
17
Widows Peak