1. Textbook Chapters 10-13 Review Book Topic 3
Genetics
Textbook Chapters 10-13
Review Book Topic 3

2. Mendelian Genetics 1866 – Gregor Mendel (Austrian monk)
Studied inheritance of traits in pea plants
Easy to grow, breed, control
“True breeding” – meaning they always produce offspring with only one form of a trait
Inheritance (heredity) – passing of traits onto
the next generation
Known as the “father of genetics”

3. Noticed that certain
characteristics are
passed onto offspring
from generation to
generation (traits)
Mendel controlled cross-
pollination (breeding)
between plants by
removing the male
organs from the flower
He then chose which
plants reproduced

4. Mendel called the
parent plants the
“P” generation
When crossing two
“P” generation, the
offspring produced
were called the “F1”
generation (hybrids)
By crossing two “F1”
generation, Mendel
could study if
characteristics could
skip generations
Creates the “F2” generation

5. Mendel studied seven different traits
Seed color
Flower color
Seed pod color
Seed shape or
texture
Seed pod shape
Stem length
Flower position

7. After his experiments Mendel concluded:
There must be two forms of a trait
Each form is controlled by an allele
Allele – alternate form of a single gene passed on from generation to generation

8. Doesn’t mean it is stronger or more present in the population
Dominant allele (A) – form of the trait that appears in the F1 generation (shown)
Doesn’t mean it is stronger
or more present in the
population
Ex. Polydactyly
Recessive allele (a) – form of the trait that is masked in the F1 generation (not shown)

9. Traits are different forms of a single gene
Genes contain a segments of DNA which codes for a specific protein

10. Law of Segregation Homologous traits occur in pairs on homologous
chromosomes
Separated from each other during gamete
formation (Law of Independent Assortment)
Recombine at fertilization
One form of a trait is inherited from each parent

12. Law of Dominance Homozygous – an organism with two of the
same alleles for a given trait (AA, aa)
Heterozygous – an organism with two
different alleles for a given trait (Aa)
When heterozygous, the dominant trait will be observed

13. Three forms of dominance:
Homozygous dominant – AA
Heterozygous – Aa
Homozygous recessive – aa

14. Characteristics The outward appearance does not always
indicate which pair of alleles is present
Genotype – organism’s allele pairs (AA,
Aa, aa)
Phenotype – observable characteristic of
an allele pair (tall, short, green, yellow)

15. It is possible for two organisms to have the
same phenotype but different genotypes
The genotype and phenotype of an
organism is called a genome

16. Activity #1
Genotype versus phenotype smiley face activity

17. Punnett Squares (1900s) Used to predict the possible offspring of a
cross between two known genotypes
Each parent contributes one allele per square in the box

18. Homozygous-homozygous AA x AA AA x aa aa x aa Homozygous-heterozygous
Monohybrid cross – only the inheritance of one
trait is being studied
Homozygous-homozygous
AA x AA
AA x aa
aa x aa
Homozygous-heterozygous
AA x Aa
aa x Aa
Heterozygous-heterozygous
Aa x Aa

22. Dihybrid cross – inheritance of two or
more different traits are being studied

24. Test Cross
An individual of unknown genotype is mated with an individual showing the homozygous recessive trait
Unknown could be homozygous or
heterozygous
Look at offspring produced to determine
unknown genotype

26. Law of Independent Assortment
Allele pairs are randomly separated
independently during gamete formation (meiosis)
Different traits are inherited separately
Exception is gene linkage
Linked genes are inherited together

27. Activity #2
Punnett square practice worksheet

28. Law of Probability “Law of chance” Inheritance of genes
can be compared to
flipping a coin
Probability = # of ways a specific event can occur
# of total possible outcomes

29. Activity #3
Probability and Inheritance Lab

30. Heredity BrainPop

31. Exceptions to Mendel’s Laws
Incomplete dominance
Both alleles contribute to the phenotype
Heterozygote is an intermediate of two parent’s traits

32. Codominance No single allele is dominant Both alleles expressed
at same time

33. Polygenic Inheritance
More than one gene can affect a single trait
Ex. Four genes are involved in eye color
Ex. Human height
Ex. Skin color

35. Pleiotrophy A single gene can affect more than one trait
Ex. Cystic fibrosis, sickle cell anemia

36. Gene Interactions (epistasis)
Products of genes
(proteins) can
interact to alter
genetic ratios
Ex. Coat color in
mammals
Ex. Purple pigment
in corn

39. Environmental Effects
Genes may be
affected by the
environment
Ex. coat color in arctic
fox or hares (rabbits)
Ex. Siamese cats

40. Multiple alleles for one gene
Genes may have more than two alleles
Ex. blood type
A, B, O alleles
Types: A, B, AB, O
IAIA / IAi (A); IBIB / IBi (B); IAIB (AB); ii (O)

42. Pedigrees
Diagram that shows the phenotypes of several generations in a family tree for a specific trait
Symbols used:
Female - 
Male – 
Shading indicates individual shows the trait
Marriage represented by horizontal line between
Offspring represented by vertical lines

44. Applied Genetics Selective Breeding
Humans breed animals/plants with certain
traits to obtain offspring that have desired traits
Results in traits becoming more
common in a breed
                                                         

45. Hybridization Animals/plants are bred to form heterozygotes
Heterozygous advantage
Ex. Disease resistance, increased offspring variation, faster growth, higher fruit yield
Disadvantages:
Time consuming
Expensive
Careful selection of parents to produce correct combinations of traits in offspring

46. Inbreeding Two closely related organisms are bred to
have the desired traits
Also to eliminate the undesired traits in future
generation
Disadvantage – harmful recessive traits also
can be passed on to future generations in
homozygous recessive individuals

48. Examples of Human Inbreeding
Ancient Egypt
Pharaohs married their sisters
Royal Europe
Royalty married within their family