Mr. Luke’s Life Science
Mendel’s Work

 Mendel experimented with thousands of pea plants
to understand the process of HEREDITY.
What Mendel Found
Definition
Heredity
The passing of physical characteristics
from parents to offspring.
Factors present within organisms that
make them different from others.
Traits or Characteristics
Mendel saw that some pea plants were tall
and some short. As well as some produced
green seed and others yellow seeds.
Genetics
The study of heredity
Crossing Pea Plants

 Mendel started his experiment crossing plants that
were PUREBRED by helping with FERTILIZATION.
What Mendel Found
Definition
Fertilization
An organism forms when an egg
and sperm join.
Purebred or Homozygous
2 identical alleles for a trait.
Mendel crossed two purebred plants.
Hybrid or Heterozygous
2 different alleles for a trait.
Mendel found that in F2 Generation
that about 75 percent of the offspring
had tall stems and 25 percent had short
stems.
Mendel’s Pea Plants

Mendel’s Conclusion

 Mendel concluded that traits get passed on by
getting a trait from the female parent and one from
the male parent.
Mendel’s Conclusion
Definition
Allele or Gene
Different forms of a gene
Dominant Allele
Mendel noticed that one factor in a pair
can mask the other factor.
The trait that always shows up in the
organism.
Represented by Upper Case letters
Recessive Allele
The trait that is hidden whenever the
dominant allele is present.
Represented by Lower Case letters
Genetics of Pea Plants

Probability & Punnett
Squares

 Probability is important, because it applies to
genetics. It predicts genetic ratio.
Genetic Probability
Definition
Probability
Predicts the results of a
particular event.
Punnett Square
Is a chart that shows all the
possible combinations of
alleles that can result from
genetic cross.
Punnett Square

Hybrid Parents
Purebred Parents
¾=
Green
¼=
White
Upper Case Letter: Dominant Allele
Lower Case Letter: Recessive Allele
Probability:
Genetic Makeup

Genetic Makeup
Definition
Phenotype
Genotype
Organism’s Physical appearance
Codominance
Alleles are neither dominant nor
recessive. Both alleles are
expressed
Organism’s allele combination
(Tt, TT, tt)
Bikini Bottom Activity

Individually, figure out
SpongeBob & Friends
genetics. Follow the
instructions on the worksheet
from H/O Box 1.
Cell Inheritance

Inheritance

 Sex cells go through a process call Meiosis to divide.
4 daughter cells are produced. With half the
chromosomes from the parents.
Sexual/Asexual
Reproduction

Types of Reproductions
Sexual Reproduction
Asexual Reproduction
Definition
Two parents combine their genetic
material to produce a new
organism, which differs from both
parents.
Only one parent produces
offspring that are identical to the
parent.
Ex.: Bacteria
Genes

 Each human body cell contains 23 chromosome
pairs or 46 chromosomes.
 Sex cells have half as many chromosomes than
body cells.
 According to the chromosome theory of
inheritance, genes are carried from parents to their
offspring on chromosomes.
Patterns of Inheritance

Allele
Definition
Single gene with Two Alleles
Determine trait with one dominant
and one recessive allele.
Ex: Widow’s peak, earlobe attached
Single gene with Multiple Alleles
Determines the trait with more than
two alleles. Three or more forms of a
gene.
Ex: Blood Type, Height, Hair Color
Sex Chromosomes

 Sex Chromosomes are one of the 23 pairs of
chromosomes in each body cell.
 It determines whether you are a boy or girl.
Human Traits Carried
on the Sex Chromosome

 These genes are called SEX-LINKED GENES.
 To get the trait a parent must be a carrier.
 Carrier: a person who has the gene
 Ex: Colorblindness
DNA & RNA

 The order of the nitrogen bases along a gene forms a
genetic code that specifies what type of protein will
be produced.
 During protein synthesis, the cell uses information
from a gene on a chromosome to produce a specific
protein.
 Before protein synthesis can take place, a
“messenger” must first carry the genetic code from
the DNA inside the nucleus into the cytoplasm. This
is RNA.
RNA

Types of RNA
Messenger RNA
Transfer RNA
Definition
Copies the coded message from the
DNA in the nucleus, and carries the
message to the ribosome in the
cytoplasm.
Carries amino acids to the ribosome
and adds them to the growing
proteins.
Mutations

 Mutation: Any change in a gene or chromosome.
 Mutations can cause a cell to produce an incorrect
protein during protein synthesis.
 Result: Organism’s trait, or phenotype, may differ
from what normally would have been.
How Mutations Happen:

 Substitution:
Addition:
 Deletion:
Genetic Disorders

 An Abnormal condition that a person inherits through
genes or chromosomes. It is caused by changes in the
overall structure of the DNA or number of chromosomes.
Types of Genetic Disorders
Definition
Cystic Fibrosis
The body produces abnormally thick
mucus in the lungs and intestines
making it hard to breathe.
Sickle-Cell Disease
When oxygen concentrations are
low, the red blood cell is an unusual
shape. It clogs blood vessels and
cannot carry as much oxygen as
normal cells. It is codominant.
Genetic Disorders

Types of Genetic Disorders
Definition
Hemophilia
A person’s blood clots very slowly or
not at all. The danger of internal
bleeding from small bumps and
bruises is very high.
A person’s cells have an extra copy of
chromosome 21. They have three
copies of a chromosome instead of two.
It can be caused by chromosomes not
separating properly during meiosis.
Down Syndrome
Genetic Disorders

Sickle-Cell Disease
Down Syndrome
Cystic Fibrosis
Hemophilia
Tracing Genetics

 Pedigree: a chart or “family tree” that tracks which
members of a family have a particular trait.
Help With Genetics

 Karotype: a picture of all the chromosomes in a cell.
 Genetic Counseling: understanding chances of child
having disorder from a genetic counselor.
Advances in Genetics

• Selective Breeding: The process of selecting organisms with
desired traits to be parents of the next generation.
Types of Selective Breeding:
Definition:
Inbreeding
Crossing two individuals that have
similar characteristics.
Inbred organisms have alleles that are
very similar to those of their parents.
Hybridization
Breeders cross two genetically different
individuals.
It is bred to have the best traits from
both parents.
Advance in Genetics

Advances in Genetics
Definition
Cloning
An organism that has exactly the same
genes the organism from which it was
produced.
You can cut a stem off of a plant and
then plant that stem. It will grow to be
exactly like the plant you cut it from.
Genetic Engineering
Genes from one organism are
transferred into the DNA of another
organism. It can produce medicines and
improve food crops.
Ex: Engineered bacteria: Insulin, helping
crops survive cold temps or poor soil,
and cows producing milk with human
gene code to help with hemophilia.