The document discusses genetics, including terms like alleles, dominant and recessive traits, genotype and phenotype. It describes Gregor Mendel's experiments with pea plants that established the laws of inheritance and segregation of traits. The document also covers sex determination and sex chromosomes, explaining how the presence of an X or Y chromosome determines whether offspring are male or female.

1. Chapter 9
Genetics
By Mr. “I love winter” Chapman

5. Intro. Genetics
 Genetics – a field of biology dedicated to
understanding how characteristics are
transmitted from parents to offspring
(heredity).
 Student Characteristics?

6. Genetics Terms
 Allele – several
alternative forms of a
gene; 2 alleles for
hair color (brown and
black hair)
 Ex. Bb

7. Genetic Terms
 Pollination – occurs
when pollen grains
(sperm) produced by
anther reach the
female reproductive
part (stigma).

8. Genetic Terms
 Self-pollination –
when pollen reaches
female part on the
same plant.

9. Genetic Terms
 Cross-pollination –
is the transfer of
pollen between two
different plants.

10. Genetics
 Gregor Mendel the father of genetics.
 Gregor Mendel experimented with peas:
 He observed different traits in peas
 Ex. Plant height, flower position, pod color, seed
color and flower color
 He noticed that purple flowered pea plants
produced purple and white flowered pea
plants.. why?

11. Mendel’s Experiments
 Began by growing plants that were pure for a
trait  they always produce offspring with that
trait (P1 Generation)
 Ex. Purple flowers purple flowers
 Cross pollinate two different traits  their
offspring is the F1 Generation
 Purple and white flowers
 F1 Generation self pollinated  their offspring
is the F2 Generation

12. Mendel’s Experiment
Mendel’s Conclusions
1. Dominant and Recessive Traits
 Dominant allele – an allele that dominates or masks
the other allele
 Ex. When a green pod allele (G) is with a yellow pod
allele (g) the green pod will result
 Recessive allele – an allele that has not observable
effect on an organism’s appearance when paired with a
dominant allele
 Ex. The yellow pod allele

14. Mendel’s Conclusions
 2. The Law of
Segregation
 paired alleles
separate during the
formation of
reproductive cells
(gametes)

15. Mendel’s Experiment
 3. The Law of Independent Assortment
 the alleles for different characteristics are
distributed to gametes independently
 A yellow pod could appear in plants
with purple or white flowers

17. Genetic Terms
 Genotype – the genetic make-up of an
organism.
 Ex. the alleles PP, Pp or pp are three
different genotypes
 Phenotype – the appearance of an
organism
 Ex. Purple flowers or White flowers

18. Example
 Purple allele is P
 White allele is p
 Genotype: PP or Pp
and pp
 Phenotype: Purple or
white

19. Genetic Terms
 Genotype – the genetic make-up of an
organism.
 Ex. the alleles PP, Pp or pp are three different
genotypes
 Phenotype – the appearance of an organism
 Ex. PP and Pp are purple flowers, pp is white
 Homozygous – the two alleles are the same
 Ex. PP or pp
 Heterozygous – the two alleles are different
 Ex. Pp

20. Genetic Terms
 Monohybrid cross – a cross between
individuals that involves one pair of traits
 Ex. crossing a plant with all purple flowers
with a plant with all white flowers.

22. Genetic Terms
 A Punnett Square is a handy dandy
device for predicting the results of a
monohybrid cross.

23. Sex Chromosomes
 Sex Determination
 Thomas Morgan (early 1900’s) bred fruit
flies and observed the sex chromosomes
 Females XX
 Males XY

24. Sex Chromosomes
 Homologous chromosomes separate
during Meiosis I
 Male gametes have either X or Y
 Female gametes have X
 When fertilization occurs who determines
the sex of the offspring?

25. Sex Chromosomes
 What is the chance that the offspring will
be female and what is the chance that
the offspring will be male?

 Sex Linkage – the presence of a gene
on the sex chromosome
 X-linked genes – genes on the X
chromosome