Genetics
The Study of Inherited
Characteristics
Ch 10.1 and Ch12
Meiosis in the Gonads
makes gametes:
Sperm
Meiotic cell
division Egg
Chromosome
DNA
Code
for
traits
Gene
Segments of Hair
Color
DNA
Code for a
trait Eye
Color
Gene
Segment
For
Hair color
Trait
Characteristic
Feature
Variations in
a population
Dominant Trait
“Dominates”
Shows in the
outward
appearance
Even when
recessive trait is
BB
present
or
Bb Bb
Recessive Trait
Albinism
“hidden”
bb May be
masked by a
dominant
trait
Bb
Alleles
Lettersof the
alphabet
Code for a
trait
One from
father
One from
mother
Dominant Recessive
Allele: Allele:
Upper case Lower case
letter of the letter of the
alphabet alphabet
Codes for Codes for
dominant recessive
traits traits
Chromosomes in Nucleus
Gene
Segments
For a
Trait=
“A” or “a”
Monohybrid Cross
Cross for
one trait Bb
Example: B BB Bb
Hair color
B BB Bb
Punnet Square
F1 Generation
Genetic
Parents
Cross=
Mating B b
BB Bb
F1=
Children
B
BB Bb
1st “filial”
generation
B
2nd Filial Generation- F2
F1= B B
Children of
the cross b Bb Bb
between the b Bb Bb
children of an
F1
F2=
“Incest”
among F1 B b
Only after B BB Bb
pure x pure
b Bb bb
Phenotype
Outward
appearance
Trait that is
shown
Bb looks brown
(has “b” =white
allele)
Genotype
Allele set
True genetic
makeup of
the
chromosome
Homozygous: Heterozygous:
Pure Hybrid
condition condition
2 same case 2 different case
alleles alleles
BB= Bb appears
dominant dominant
bb= recessive
Mendelian Genetics Review:
See Encarta CD-ROM
Dihybrid Cross
Cross with
two traits parents
Example: Children Children Children Children
1. Hair Color Children Children Children Children
2. Eye Color
Children Children Children Children
2 types of
Children Children Children Children
alleles
Codominance
“Incomplete”
Pink Carnation
dominance
Hybrid is a blend of
traits
Example:
RR=red
Rr=pink
rr=white
Multiple Alleles
More than TYPES:
one type of A IAIA, IAi
allele for a B IBIB , IBi
trait AB IAIB
Example: O ii
Blood Type
X-Linked Traits
Female=
Sex-linked XX
Traitin on the sex Add eye trait=
chromosome XRXR or XRXr
XX= XrXr
Female Male=
XY XY
Male Add eye trait=
XRY or XrY
Ex:Red & white
eyes “Y” is empty
Karyotype
Chromosome Number
Homologous
Different # for different
species
Chromosomes
Full set = 2N=Diploid
are the sets of
N=
each pair
# pairs
1 pair from mother
1 pair from father
Humans= 23 pairs or
46 total
Autosomes & Sex Chromosomes
Autosomes = # 1-
22 for all traits
except sex
Sex chromosomes=
Pair # 23 XX(female) or
XY(male)
Down Syndrome= 3 of #21
Klinefelter’s = XXY
Pedigree Charts
Male =
Female=
Sexual Union=
Offspring=
Pedigree Chart -Cystic Fibrosis
Mutation
Change in DNA A A
code T to A
Caused by: G
G
1. Chemical damage C
2. Errors in
C
Replication
3. X-ray damage
4. UV damage
Mutation
Changes in
the DNA code
= Changes in
the final
proteins made
=Changes in
the organism